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Macias S, Bakshi K, Smotherman M. Laminar Organization of FM Direction Selectivity in the Primary Auditory Cortex of the Free-Tailed Bat. Front Neural Circuits 2019; 13:76. [PMID: 31827425 PMCID: PMC6890848 DOI: 10.3389/fncir.2019.00076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 11/13/2019] [Indexed: 01/18/2023] Open
Abstract
We studied the columnar and layer-specific response properties of neurons in the primary auditory cortex (A1) of six (four females, two males) anesthetized free-tailed bats, Tadarida brasiliensis, in response to pure tones and down and upward frequency modulated (FM; 50 kHz bandwidth) sweeps. In addition, we calculated current source density (CSD) to test whether lateral intracortical projections facilitate neuronal activation in response to FM echoes containing spectrally distant frequencies from the excitatory frequency response area (FRA). Auditory responses to a set of stimuli changing in frequency and level were recorded along 64 penetrations in the left A1 of six free-tailed bats. FRA shapes were consistent across the cortical depth within a column and there were no obvious differences in tuning properties. Generally, response latencies were shorter (<10 ms) for cortical depths between 500 and 600 μm, which might correspond to thalamocortical input layers IIIb-IV. Most units showed a stronger response to downward FM sweeps, and direction selectivity did not vary across cortical depth. CSD profiles calculated in response to the CF showed a current sink located at depths between 500 and 600 μm. Frequencies lower than the frequency range eliciting a spike response failed to evoke any visible current sink. Frequencies higher than the frequency range producing a spike response evoked layer IV sinks at longer latencies that increased with spectral distance. These data support the hypothesis that a progressive downward relay of spectral information spreads along the tonotopic axis of A1 via lateral connections, contributing to the neural processing of FM down sweeps used in biosonar.
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Affiliation(s)
- Silvio Macias
- Department of Biology, Texas A&M University, College Station, TX, United States
| | - Kushal Bakshi
- Department of Biology, Texas A&M University, College Station, TX, United States
| | - Michael Smotherman
- Department of Biology, Texas A&M University, College Station, TX, United States
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2
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Korzyukov O, Bronder A, Lee Y, Patel S, Larson CR. Bioelectrical brain effects of one's own voice identification in pitch of voice auditory feedback. Neuropsychologia 2017; 101:106-114. [PMID: 28461225 DOI: 10.1016/j.neuropsychologia.2017.04.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Revised: 03/04/2017] [Accepted: 04/27/2017] [Indexed: 01/22/2023]
Abstract
Control of voice fundamental frequency (F0) relies in part on comparison of the intended F0 level and auditory feedback. This comparison impacts "sense of agency", or SoA, commonly defined as being the agent of one's own actions and plays a key role for self-awareness and social interactions. SoA is aberrant in several psychiatric disorders. Knowledge about brain activity reflecting SoA can be used in clinical practice for these disorders. It was shown that perception of voice feedback as one's own voice, reflecting the recognition of SoA, alters auditory sensory processing. Using a voice perturbation paradigm we contrasted vocal and bioelectrical brain responses to auditory stimuli that differed in magnitude: 100 and 400 cents. Results suggest the different magnitudes were perceived as a pitch error in self-vocalization (100 cents) or as a pitch shift generated externally (400 cents). Vocalizations and neural responses to changes in pitch of self-vocalization were defined as those made to small magnitude pitch-shifts (100 cents) and which did not show differential neural responses to upward versus downward changes in voice pitch auditory feedback. Vocal responses to large magnitude pitch shifts (400 cents) were smaller than those made to small pitch shifts, and neural responses differed according to upwards versus downward changes in pitch. Our results suggest that the presence of SoA for self-produced sounds may modify bioelectrical brain responses reflecting differences in auditory processing of the direction of a pitch shift. We suggest that this modification of bioelectrical response can be used as a biological index of SoA. Possible neuronal mechanisms of this modification of bioelectrical brain response are discussed.
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Affiliation(s)
- Oleg Korzyukov
- Department of Communication Sciences and Disorders, Northwestern University, 2240 Campus Dr., Evanston, IL 60208, USA; Neuromagnetic Brain Imaging Laboratory, Meadowlands Medical Center, 55 Meadowlands Parkway, Secaucus, NJ 07094, USA.
| | - Alexander Bronder
- Department of Communication Sciences and Disorders, Northwestern University, 2240 Campus Dr., Evanston, IL 60208, USA
| | - Yunseon Lee
- Department of Communication Sciences and Disorders, Northwestern University, 2240 Campus Dr., Evanston, IL 60208, USA
| | - Sona Patel
- Department of Speech-Language Pathology, Seton Hall University, 400 South Orange Ave, South Orange, NJ 07079, USA
| | - Charles R Larson
- Department of Communication Sciences and Disorders, Northwestern University, 2240 Campus Dr., Evanston, IL 60208, USA
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3
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Kumar V, Nag TC, Sharma U, Mewar S, Jagannathan NR, Wadhwa S. High resolution 1H NMR-based metabonomic study of the auditory cortex analogue of developing chick (Gallus gallus domesticus) following prenatal chronic loud music and noise exposure. Neurochem Int 2014; 76:99-108. [DOI: 10.1016/j.neuint.2014.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 06/16/2014] [Accepted: 07/04/2014] [Indexed: 02/07/2023]
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4
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Differential effects of prenatal chronic high-decibel noise and music exposure on the excitatory and inhibitory synaptic components of the auditory cortex analog in developing chicks (Gallus gallus domesticus). Neuroscience 2014; 269:302-17. [DOI: 10.1016/j.neuroscience.2014.03.061] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 03/28/2014] [Accepted: 03/28/2014] [Indexed: 02/06/2023]
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Abstract
Complex natural and environmental sounds, such as speech and music, convey information along both spectral and temporal dimensions. The cortical representation of such stimuli rapidly adapts when animals become actively engaged in discriminating them. In this study, we examine the nature of these changes using simplified spectrotemporal versions (upward vs downward shifting tone sequences) with domestic ferrets (Mustela putorius). Cortical processing rapidly adapted to enhance the contrast between the two discriminated stimulus categories, by changing spectrotemporal receptive field properties to encode both the spectral and temporal structure of the tone sequences. Furthermore, the valence of the changes was closely linked to the task reward structure: stimuli associated with negative reward became enhanced relative to those associated with positive reward. These task- and-stimulus-related spectrotemporal receptive field changes occurred only in trained animals during, and immediately following, behavior. This plasticity was independently confirmed by parallel changes in a directionality function measured from the responses to the transition of tone sequences during task performance. The results demonstrate that induced patterns of rapid plasticity reflect closely the spectrotemporal structure of the task stimuli, thus extending the functional relevance of rapid task-related plasticity to the perception and learning of natural sounds such speech and animal vocalizations.
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Yokota R, Aihara K, Kanzaki R, Takahashi H. Learning-stage-dependent plasticity of temporal coherence in the auditory cortex of rats. Brain Topogr 2014; 28:401-10. [PMID: 24615394 DOI: 10.1007/s10548-014-0359-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 02/20/2014] [Indexed: 10/25/2022]
Abstract
Temporal coherence among neural populations may contribute importantly to signal encoding, specifically by providing an optimal tradeoff between encoding reliability and efficiency. Here, we considered the possibility that learning modulates the temporal coherence among neural populations in association with well-characterized map plasticity. We previously demonstrated that, in appetitive operant conditioning tasks, the tone-responsive area globally expanded during the early stage of learning, but shrank during the late stage. The present study further showed that phase locking of the first spike to band-specific oscillations of local field potentials (LFPs) significantly increased during the early stage of learning but decreased during the late stage, suggesting that neurons in A1 were more synchronously activated during early learning, whereas they were more asynchronously activated once learning was completed. Furthermore, LFP amplitudes increased during early learning but decreased during later learning. These results suggest that, compared to naïve encoding, early-stage encoding is more reliable but energy-consumptive, whereas late-stage encoding is more energetically efficient. Such a learning-stage-dependent encoding strategy may underlie learning-induced, non-monotonic map plasticity. Accumulating evidence indicates that the cholinergic system is likely to be a shared neural substrate of the processes for perceptual learning and attention, both of which modulate neural encoding in an adaptive manner. Thus, a better understanding of the links between map plasticity and modulation of temporal coherence will likely lead to a more integrated view of learning and attention.
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Affiliation(s)
- Ryo Yokota
- Research Center for Advanced Science and Technology, The University of Tokyo, Komaba 4-6-1, Meguro-ku, Tokyo, 153-8904, Japan
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7
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Abstract
Receptive fields (RFs) of neurons in primary visual cortex have traditionally been subdivided into two major classes: "simple" and "complex" cells. Simple cells were originally defined by the existence of segregated subregions within their RF that respond to either the on- or offset of a light bar and by spatial summation within each of these regions, whereas complex cells had ON and OFF regions that were coextensive in space [Hubel DH, et al. (1962) J Physiol 160:106-154]. Although other definitions based on the linearity of response modulation have been proposed later [Movshon JA, et al. (1978) J Physiol 283:53-77; Skottun BC, et al. (1991) Vision Res 31(7-8):1079-1086], the segregation of ON and OFF subregions has remained an important criterion for the distinction between simple and complex cells. Here we report that response profiles of neurons in primary auditory cortex of monkeys show a similar distinction: one group of cells has segregated ON and OFF subregions in frequency space; and another group shows ON and OFF responses within largely overlapping response profiles. This observation is intriguing for two reasons: (i) spectrotemporal dissociation in the auditory domain provides a basic neural mechanism for the segregation of sounds, a fundamental prerequisite for auditory figure-ground discrimination; and (ii) the existence of similar types of RF organization in visual and auditory cortex would support the existence of a common canonical processing algorithm within cortical columns.
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Washington SD, Kanwal JS. Sex-dependent hemispheric asymmetries for processing frequency-modulated sounds in the primary auditory cortex of the mustached bat. J Neurophysiol 2012; 108:1548-66. [PMID: 22649207 PMCID: PMC3544949 DOI: 10.1152/jn.00952.2011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 05/26/2012] [Indexed: 11/22/2022] Open
Abstract
Species-specific vocalizations of mammals, including humans, contain slow and fast frequency modulations (FMs) as well as tone and noise bursts. In this study, we established sex-specific hemispheric differences in the tonal and FM response characteristics of neurons in the Doppler-shifted constant-frequency processing area in the mustached bat's primary auditory cortex (A1). We recorded single-unit cortical activity from the right and left A1 in awake bats in response to the presentation of tone bursts and linear FM sweeps that are contained within their echolocation and/or communication sounds. Peak response latencies to neurons' preferred or best FMs were significantly longer on the right compared with the left in both sexes, and in males this right-left difference was also present for the most excitatory tone burst. Based on peak response magnitudes, right hemispheric A1 neurons in males preferred low-rate, narrowband FMs, whereas those on the left were less selective, responding to FMs with a variety of rates and bandwidths. The distributions of parameters for best FMs in females were similar on the two sides. Together, our data provide the first strong physiological support of a sex-specific, spectrotemporal hemispheric asymmetry for the representation of tones and FMs in a nonhuman mammal. Specifically, our results demonstrate a left hemispheric bias in males for the representation of a diverse array of FMs differing in rate and bandwidth. We propose that these asymmetries underlie lateralized processing of communication sounds and are common to species as divergent as bats and humans.
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Affiliation(s)
- Stuart D Washington
- 1Department of Physiology and Biophysics, Georgetown University Medical Center, Washington, District of Columbia, USA
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Williams AJ, Fuzessery ZM. Multiple mechanisms shape FM sweep rate selectivity: complementary or redundant? Front Neural Circuits 2012; 6:54. [PMID: 22912604 PMCID: PMC3421451 DOI: 10.3389/fncir.2012.00054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 07/30/2012] [Indexed: 11/16/2022] Open
Abstract
Auditory neurons in the inferior colliculus (IC) of the pallid bat have highly rate selective responses to downward frequency modulated (FM) sweeps attributable to the spectrotemporal pattern of their echolocation call (a brief FM pulse). Several mechanisms are known to shape FM rate selectivity within the pallid bat IC. Here we explore how two mechanisms, stimulus duration and high-frequency inhibition (HFI), can interact to shape FM rate selectivity within the same neuron. Results from extracellular recordings indicated that a derived duration-rate function (based on tonal response) was highly predictive of the shape of the FM rate response. Longpass duration selectivity for tones was predictive of slowpass rate selectivity for FM sweeps, both of which required long stimulus durations and remained intact following iontophoretic blockade of inhibitory input. Bandpass duration selectivity for tones, sensitive to only a narrow range of tone durations, was predictive of bandpass rate selectivity for FM sweeps. Conversion of the tone duration response from bandpass to longpass after blocking inhibition was coincident with a change in FM rate selectivity from bandpass to slowpass indicating an active inhibitory component to the formation of bandpass selectivity. Independent of the effect of duration tuning on FM rate selectivity, the presence of HFI acted as a fastpass FM rate filter by suppressing slow FM sweep rates. In cases where both mechanisms were present, both had to be eliminated, by removing inhibition, before bandpass FM rate selectivity was affected. It is unknown why the auditory system utilizes multiple mechanisms capable of shaping identical forms of FM rate selectivity though it may represent distinct but convergent modes of neural signaling directed at shaping response selectivity for important biologically relevant sounds.
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Affiliation(s)
- Anthony J Williams
- Department of Zoology and Physiology, University of Wyoming Laramie, WY, USA
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Zhang LI, Zhou Y, Tao HW. Perspectives on: information and coding in mammalian sensory physiology: inhibitory synaptic mechanisms underlying functional diversity in auditory cortex. ACTA ACUST UNITED AC 2012; 138:311-20. [PMID: 21875980 PMCID: PMC3171074 DOI: 10.1085/jgp.201110650] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Li I Zhang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, USA.
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11
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Razak KA. Mechanisms underlying intensity-dependent changes in cortical selectivity for frequency-modulated sweeps. J Neurophysiol 2012; 107:2202-11. [PMID: 22279192 DOI: 10.1152/jn.00922.2011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Frequency-modulated (FM) sweeps are common components of species-specific vocalizations. The intensity of FM sweeps can cover a wide range in the natural environment, but whether intensity affects neural selectivity for FM sweeps is unclear. Bats, such as the pallid bat, which use FM sweeps for echolocation, are suited to address this issue, because the intensity of echoes will vary with target distance. In this study, FM sweep rate selectivity of pallid bat auditory cortex neurons was measured using downward sweeps at different intensities. Neurons became more selective for FM sweep rates present in the bat's echolocation calls as intensity increased. Increased selectivity resulted from stronger inhibition of responses to slower sweep rates. The timing and bandwidth of inhibition generated by frequencies on the high side of the excitatory tuning curve [sideband high-frequency inhibition (HFI)] shape rate selectivity in cortical neurons in the pallid bat. To determine whether intensity-dependent changes in FM rate selectivity were due to altered inhibition, the timing and bandwidth of HFI were quantified at multiple intensities using the two-tone inhibition paradigm. HFI arrived faster relative to excitation as sound intensity increased. The bandwidth of HFI also increased with intensity. The changes in HFI predicted intensity-dependent changes in FM rate selectivity. These data suggest that neural selectivity for a sweep parameter is not static but shifts with intensity due to changes in properties of sideband inhibition.
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Affiliation(s)
- K A Razak
- Dept. of Psychology, Graduate Neuroscience Program, Univ. of California, Riverside, CA 92521, USA.
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12
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Sanes DH, Woolley SMN. A behavioral framework to guide research on central auditory development and plasticity. Neuron 2011; 72:912-29. [PMID: 22196328 PMCID: PMC3244881 DOI: 10.1016/j.neuron.2011.12.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2011] [Indexed: 01/14/2023]
Abstract
The auditory CNS is influenced profoundly by sounds heard during development. Auditory deprivation and augmented sound exposure can each perturb the maturation of neural computations as well as their underlying synaptic properties. However, we have learned little about the emergence of perceptual skills in these same model systems, and especially how perception is influenced by early acoustic experience. Here, we argue that developmental studies must take greater advantage of behavioral benchmarks. We discuss quantitative measures of perceptual development and suggest how they can play a much larger role in guiding experimental design. Most importantly, including behavioral measures will allow us to establish empirical connections among environment, neural development, and perception.
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Affiliation(s)
- Dan H Sanes
- Center for Neural Science, 4 Washington Place, New York University, New York, NY 10003, USA.
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Williams AJ, Fuzessery ZM. Differential roles of GABAergic and glycinergic input on FM selectivity in the inferior colliculus of the pallid bat. J Neurophysiol 2011; 106:2523-35. [PMID: 21775712 DOI: 10.1152/jn.00569.2011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Multiple mechanisms have been shown to shape frequency-modulated (FM) selectivity within the central nucleus of the inferior colliculus (IC) in the pallid bat. In this study we focus on the mechanisms associated with sideband inhibition. The relative arrival time of inhibition compared with excitation can be used to predict FM responses as measured with a two-tone inhibition paradigm. An early-arriving low-frequency inhibition (LFI) prevents responses to upward sweeps and thus shapes direction selectivity. A late-arriving high-frequency inhibition (HFI) suppresses slow FM sweeps and thus shapes rate selectivity for downward sweeps. Iontophoretic application of gabazine (GBZ) to block GABA(A) receptors or strychnine (Strych) to block glycine receptors was used to assess the effects of removal of inhibition on each form of FM selectivity. GBZ and Strych had a similar effect on FM direction selectivity, reducing selectivity in up to 86% of neurons when both drugs were coapplied. FM rate selectivity was more resistant to drug application with less than 38% of neurons affected. In addition, only Strych could eliminate FM rate selectivity, whereas GBZ alone was ineffective. The loss of FM selectivity was directly correlated to a loss of the respective inhibitory sideband that shapes that form of selectivity. The elimination of LFI correlated to a loss of FM direction selectivity, whereas elimination of HFI correlated to a loss of FM rate selectivity. Results indicate that 1) although the majority of FM direction selectivity is created within the IC, the majority of rate selectivity is inherited from lower levels of the auditory system, 2) a loss of LFI corresponds to a loss of FM direction selectivity and is created through either GABAergic or glycinergic input, and 3) a loss of HFI corresponds to a loss of FM rate selectivity and is created mainly through glycinergic input.
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Affiliation(s)
- Anthony J Williams
- Dept. of Zoology and Physiology, Univ. of Wyoming, 1000 E. Univ. Ave., Laramie, WY 82071, USA
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Wu GK, Tao HW, Zhang LI. From elementary synaptic circuits to information processing in primary auditory cortex. Neurosci Biobehav Rev 2011; 35:2094-104. [PMID: 21609731 DOI: 10.1016/j.neubiorev.2011.05.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 05/04/2011] [Accepted: 05/09/2011] [Indexed: 11/25/2022]
Abstract
A key for understanding how information is processed in the cortex is to unravel the dauntingly complex cortical neural circuitry. Recent technical innovations, in particular the in vivo whole-cell voltage-clamp recording techniques, make it possible to directly dissect the excitatory and inhibitory inputs underlying an individual cortical neuron's processing function. This method provides an essential complement to conventional approaches, with which the transfer functions of the neural system are derived by correlating neuronal spike outputs to sensory inputs. Here, we intend to introduce a potentially systematic strategy for resolving the structure of functional synaptic circuits. As complex circuits can be built upon elementary modules, the primary focus of this strategy is to identify elementary synaptic circuits and determine how these circuit units contribute to specific processing functions. This review will summarize recent studies on functional synaptic circuits in the primary auditory cortex, comment on existing experimental techniques for in vivo circuitry studies, and provide a perspective on immediate future directions.
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Affiliation(s)
- Guangying K Wu
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, United States
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15
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A bird brain's view of auditory processing and perception. Hear Res 2010; 273:123-33. [PMID: 20851756 DOI: 10.1016/j.heares.2010.08.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 08/12/2010] [Accepted: 08/14/2010] [Indexed: 11/24/2022]
Abstract
By studying the primary forebrain auditory area of songbirds, field L, using a song-inspired synthetic stimulus and reverse correlation techniques, we found a surprisingly systematic organization of this area, with nearly all neurons narrowly tuned along the spectral dimension, the temporal dimension, or both; there were virtually no strongly orientation-sensitive cells, and in the areas that we recorded, cells broadly tuned in both time and frequency were rare. In addition, cells responsive to fast temporal frequencies predominated only in the field L input layer, suggesting that neurons with fast and slow responses are concentrated in different regions. Together with other songbird data and work from chicks and mammals, these findings suggest that sampling a range of temporal and spectral modulations, rather than orientation in time-frequency space, is the organizing principle of forebrain auditory sensitivity. We then examined the role of these acoustic parameters important to field L organization in a behavioral task. Birds' categorization of songs fell off rapidly when songs were altered in frequency, but, despite the temporal sensitivity of field L neurons, the same birds generalized well to songs that were significantly changed in timing. These behavioral data point out that we cannot assume that animals use the information present in particular neurons without specifically testing perception.
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Williams AJ, Fuzessery ZM. Facilitatory mechanisms shape selectivity for the rate and direction of FM sweeps in the inferior colliculus of the pallid bat. J Neurophysiol 2010; 104:1456-71. [PMID: 20631213 DOI: 10.1152/jn.00598.2009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The inferior colliculus (IC) of the pallid bat has a large percentage of neurons that respond selectively to the rate and direction of the bat's echolocation pulse, a downward FM sweep. Three underlying mechanisms have been previously described. Here we describe a fourth mechanism, facilitation, that shapes selectivity for both sweep rate and direction. The neurons studied are termed FM specialists, because they do not respond to tones. Most were selective for the downward sweep direction, and this preference was expressed even when presented with narrowband, 1 kHz sweeps that crossed only a fraction of their excitatory receptive fields. This selectivity was also expressed in response to two tones delayed in time, termed two-tone facilitation (TTF). Direction-selective neurons showed a greatly facilitated response when a higher-frequency tone preceded a lower-frequency tone, simulating conditions in a downward sweep. The degree of temporal asymmetry in facilitation accurately predicted direction selectivity. When the spectral difference between the two tones was increased, the best delay also increased and could be used to predict a neuron's preferred sweep rate. To determine whether TTF alone created rate and direction selectivity, low- and high-frequency inhibitory sidebands, which can also shape selectivity, were eliminated from sweeps. In most cases, selectivity persisted. These results support the idea of spectral delay lines that produce an overlap and summation of excitatory inputs only when a dynamic stimulus traverses a receptive field in one direction at a specific velocity.
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Affiliation(s)
- Anthony J Williams
- Dept. of Zoology and Physiology, Univ. of Wyoming, Laramie, WY 82071, USA
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Fuzessery ZM, Razak KA, Williams AJ. Multiple mechanisms shape selectivity for FM sweep rate and direction in the pallid bat inferior colliculus and auditory cortex. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2010; 197:615-23. [PMID: 20596868 DOI: 10.1007/s00359-010-0554-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 06/18/2010] [Accepted: 06/19/2010] [Indexed: 12/21/2022]
Abstract
The inferior colliculus and auditory cortex of the pallid bat contain a large percentage of neurons that are highly selective for the direction and rate of the downward frequency modulated (FM) sweep of the bat's echolocation pulse. Approximately 25% of neurons tuned to the echolocation pulse respond exclusively to downward FM sweeps. This review focuses on the finding that this selectivity is generated by multiple mechanisms that may act alone or in concert. In the inferior colliculus, selectivity for sweep rate is shaped by at least three mechanisms: shortpass or bandpass tuning for signal duration, delayed high-frequency inhibition that prevents responses to slow sweep rates, and asymmetrical facilitation that occurs only when two tones are presented at appropriate delays. When acting alone, the three mechanisms can produce essentially identical rate selectivity. Direction selectivity can be produced by two mechanisms: an early low-frequency inhibition that prevents responses to upward sweeps, and the same asymmetrical two-tone inhibition that shapes rate tuning. All mechanisms except duration tuning are also present in the auditory cortex. Discussion centers on whether these mechanisms are redundant or complementary.
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Affiliation(s)
- Zoltan M Fuzessery
- Department 3166, Zoology and Physiology, University of Wyoming, 1000 E. University Ave, Laramie, WY 82071, USA.
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18
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Ma J, Naumann RT, Kanwal JS. Fear conditioned discrimination of frequency modulated sweeps within species-specific calls of mustached bats. PLoS One 2010; 5:e10579. [PMID: 20485675 PMCID: PMC2868862 DOI: 10.1371/journal.pone.0010579] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 04/07/2010] [Indexed: 11/19/2022] Open
Abstract
Social and echolocation vocalizations of bats contain different patterns of frequency modulations. An adult bat's ability to discriminate between various FM parameters, however, is not well established. Using changes in heart rate (HR) as a quantitative measure of associative learning, we demonstrate that mustached bats (Pteronotus parnellii) can be fear conditioned to linear frequency modulated (FM) sweeps typically centered at their acoustic fovea (approximately 60 kHz). We also show that HR is sensitive to a change in the direction of the conditional frequency modulation keeping all other parameters constant. In addition, a change in either depth or duration co-varied with FM rate is reflected in the change in HR. Finally, HR increases linearly with FM rate incremented by 0.1 kHz/ms from a pure tone to a target rate of 1.0 kHz/ms of the conditional stimulus. Learning is relatively rapid, occurring after a single training session. We also observed that fear conditioning enhances local field potential activity within the basolateral amygdala. Neural response enhancement coinciding with rapid learning and a fine scale cortical representation of FM sweeps shown earlier make FMs prime candidates for discriminating between different call types and possibly communicating socially relevant information within species-specific sounds.
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Affiliation(s)
- Jie Ma
- Department of Physiology and Biophysics, Georgetown University, Washington, D. C., United States of America
| | - Robert T. Naumann
- Department of Physiology and Biophysics, Georgetown University, Washington, D. C., United States of America
| | - Jagmeet S. Kanwal
- Department of Physiology and Biophysics, Georgetown University, Washington, D. C., United States of America
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19
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Scholl B, Gao X, Wehr M. Nonoverlapping sets of synapses drive on responses and off responses in auditory cortex. Neuron 2010; 65:412-21. [PMID: 20159453 DOI: 10.1016/j.neuron.2010.01.020] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/14/2010] [Indexed: 10/19/2022]
Abstract
Neurons in visual, somatosensory, and auditory cortex can respond to the termination as well as the onset of a sensory stimulus. In auditory cortex, these off responses may underlie the ability of the auditory system to use sound offsets as cues for perceptual grouping. Off responses have been widely proposed to arise from postinhibitory rebound, but this hypothesis has never been directly tested. We used in vivo whole-cell recordings to measure the synaptic inhibition evoked by sound onset. We find that inhibition is invariably transient, indicating that off responses are not caused by postinhibitory rebound in auditory cortical neurons. Instead, on and off responses appear to be driven by distinct sets of synapses, because they have distinct frequency tuning and different excitatory-inhibitory balance. Furthermore, an on-on sequence causes complete forward suppression, whereas an off-on sequence causes no suppression at all. We conclude that on and off responses are driven by largely nonoverlapping sets of synaptic inputs.
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Affiliation(s)
- Ben Scholl
- Institute of Neuroscience, Department of Psychology, University of Oregon, Eugene, OR 97403, USA
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20
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Insanally MN, Albanna BF, Bao S. Pulsed noise experience disrupts complex sound representations. J Neurophysiol 2010; 103:2611-7. [PMID: 20200123 DOI: 10.1152/jn.00872.2009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cortical sound representations are adapted to the acoustic environment. Early exposure to exponential frequency-modulated (FM) sweeps results in more neurons selective to the experienced sounds. Here we examined the influence of pulsed noise experience on the development of sound representations in the primary auditory cortex (AI) of the rat. In naïve animals, FM sweep direction selectivity depends on the characteristic frequency (CF) of the neuron--low CF neurons tend to select for upward sweeps and high CF neurons for downward sweeps. Such a CF dependence was not observed in animals that had received weeklong exposure to pulsed noise in periods from postnatal day 8 (P8) to P15 or from P24 to P39. In addition, AI tonotopicity, tuning bandwidth, intensity threshold, tone-responsiveness, and sweep response magnitude were differentially affected by the noise experience depending on the exposure time windows. These results are consistent with previous findings of feature-dependent multiple sensitive periods. The different effects induced here by pulsed noise and previously by FM sweeps further indicate that plasticity in cortical complex sound representations is specific to the sensory input.
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Affiliation(s)
- Michele N Insanally
- Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720-3190, USA
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21
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Facilitatory mechanisms underlying selectivity for the direction and rate of frequency modulated sweeps in the auditory cortex. J Neurosci 2008; 28:9806-16. [PMID: 18815265 DOI: 10.1523/jneurosci.1293-08.2008] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurons selective for frequency modulated (FM) sweeps are common in auditory systems across different vertebrate groups and may underlie representation of species-specific vocalizations. Studies on mechanisms of FM sweep selectivity have primarily focused on sideband inhibition. Here, we present the first evidence for facilitatory mechanisms of FM sweep selectivity. Facilitatory interactions were found in 46 of 264 (17%) neurons tuned in the echolocation range (25-60 kHz) in the auditory cortex of the pallid bat. These neurons respond poorly to individual tones but are facilitated by combinations of tones with specific spectral and temporal intervals. Facilitation neurons show remarkable sensitivity to sub-millisecond differences in time delays between the two tones. Interestingly, the range of delays eliciting facilitation is not fixed but varies systematically with frequency difference between the two tones. Properties of facilitation strongly predict selectivity for the direction and rate of FM sweeps. Together with previous studies, there appear to be at least three mechanisms underlying FM rate and direction selectivity: sideband inhibition, duration tuning, and facilitation. Interestingly, similar mechanisms underlie direction and velocity tuning in the visual system, suggesting the evolution of similar computations across sensory systems to process dynamic sensory stimuli.
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22
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Qin L, Wang J, Sato Y. Heterogeneous Neuronal Responses to Frequency-Modulated Tones in the Primary Auditory Cortex of Awake Cats. J Neurophysiol 2008; 100:1622-34. [DOI: 10.1152/jn.90364.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies in anesthetized animals reported that the primary auditory cortex (A1) showed homogenous phasic responses to FM tones, namely a transient response to a particular instantaneous frequency when FM sweeps traversed a neuron's tone-evoked receptive field (TRF). Here, in awake cats, we report that A1 cells exhibit heterogeneous FM responses, consisting of three patterns. The first is continuous firing when a slow FM sweep traverses the receptive field of a cell with a sustained tonal response. The duration and amplitude of FM response decrease with increasing sweep speed. The second pattern is transient firing corresponding to the cell's phasic tonal response. This response could be evoked only by a fast FM sweep through the cell's TRF, suggesting a preference for fast FM. The third pattern was associated with the off response to pure tones and was composed of several discrete response peaks during slow FM stimulus. These peaks were not predictable from the cell's tonal response but reliably reflected the time when FM swept across specific frequencies. Our A1 samples often exhibited a complex response pattern, combining two or three of the basic patterns above, resulting in a heterogeneous response population. The diversity of FM responses suggests that A1 use multiple mechanisms to fully represent the whole range of FM parameters, including frequency extent, sweep speed, and direction.
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23
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König R, Sieluzycki C, Simserides C, Heil P, Scheich H. Effects of the task of categorizing FM direction on auditory evoked magnetic fields in the human auditory cortex. Brain Res 2008; 1220:102-17. [PMID: 18420183 DOI: 10.1016/j.brainres.2008.02.086] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Revised: 02/25/2008] [Accepted: 02/27/2008] [Indexed: 10/22/2022]
Abstract
We examined effects of the task of categorizing linear frequency-modulated (FM) sweeps into rising and falling on auditory evoked magnetic fields (AEFs) from the human auditory cortex, recorded by means of whole-head magnetoencephalography. AEFs in this task condition were compared with those in a passive condition where subjects had been asked to just passively listen to the same stimulus material. We found that the M100-peak latency was significantly shorter for the task condition than for the passive condition in the left but not in the right hemisphere. Furthermore, the M100-peak latency was significantly shorter in the right than in the left hemisphere for the passive and the task conditions. In contrast, the M100-peak amplitude did not differ significantly between conditions, nor between hemispheres. We also analyzed the activation strength derived from the integral of the absolute magnetic field over constant time windows between stimulus onset and 260 ms. We isolated an early, narrow time range between about 60 ms and 80 ms that showed larger values in the task condition, most prominently in the right hemisphere. These results add to other imaging and lesion studies which suggest a specific role of the right auditory cortex in identifying FM sweep direction and thus in categorizing FM sweeps into rising and falling.
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Affiliation(s)
- Reinhard König
- Leibniz Institute for Neurobiology, Brenneckestrasse 6, 39118 Magdeburg, Germany
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24
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Atencio CA, Blake DT, Strata F, Cheung SW, Merzenich MM, Schreiner CE. Frequency-modulation encoding in the primary auditory cortex of the awake owl monkey. J Neurophysiol 2007; 98:2182-95. [PMID: 17699695 DOI: 10.1152/jn.00394.2007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many communication sounds, such as New World monkey twitter calls, contain frequency-modulated (FM) sweeps. To determine how this prominent vocalization element is represented in the auditory cortex we examined neural responses to logarithmic FM sweep stimuli in the primary auditory cortex (AI) of two awake owl monkeys. Using an implanted array of microelectrodes we quantitatively characterized neuronal responses to FM sweeps and to random tone-pip stimuli. Tone-pip responses were used to construct spectrotemporal receptive fields (STRFs). Classification of FM sweep responses revealed few neurons with high direction and speed selectivity. Most neurons responded to sweeps in both directions and over a broad range of sweep speeds. Characteristic frequency estimates from FM responses were highly correlated with estimates from STRFs, although spectral receptive field bandwidth was consistently underestimated by FM stimuli. Predictions of FM direction selectivity and best speed from STRFs were significantly correlated with observed FM responses, although some systematic discrepancies existed. Last, the population distributions of FM responses in the awake owl monkey were similar to, although of longer temporal duration than, those in the anesthetized squirrel monkeys.
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Affiliation(s)
- Craig A Atencio
- Bioengineering Graduate Group, University of California San Francisco, San Francisco, CA 94143-0732, USA.
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25
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Voytenko SV, Galazyuk AV. Intracellular recording reveals temporal integration in inferior colliculus neurons of awake bats. J Neurophysiol 2006; 97:1368-78. [PMID: 17135472 DOI: 10.1152/jn.00976.2006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The central nucleus of the inferior colliculus (IC) is a major integrative center in the central auditory system. It receives information from both the ascending and descending auditory pathways. To determine how single IC neurons integrate information over a wide range of sound frequencies and sound levels, we examined their intracellular responses to frequency-modulated (FM) sounds in awake little brown bats (Myotis lucifugus). Postsynaptic potentials were recorded in response to downward FM sweeps of the range typical for little brown bats (80-20 kHz) and to three FM subcomponents (80-60, 60-40, and 40-20 kHz). The majority of recorded neurons responded to the 80- to 20-kHz downward FM sweep with a complex response. In this response an initial hyperpolarization was followed by depolarization with or without spike followed by hyperpolarization. Intracellular recordings in response to three FM subcomponents revealed that these neurons receive excitatory and inhibitory inputs from a wide range of sound frequencies. One third of IC neurons performed nearly linear temporal summation across a wide range of sound frequencies, whereas two thirds of IC neurons exhibited nonlinear summation with different degrees of nonlinearity. Some IC neurons showed different latencies of postsynaptic potentials in response to different FM subcomponents. Often responses to the later FM subcomponent occurred before responses to the earlier ones. This phenomenon may be responsible for response selectivity of IC neurons to FM sweeps.
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Affiliation(s)
- S V Voytenko
- Department of Neurobiology, Northeastern Ohio Universities College of Medicine, 4209 State Route 44, Rootstown, OH 44272, USA
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26
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Fuzessery ZM, Richardson MD, Coburn MS. Neural mechanisms underlying selectivity for the rate and direction of frequency-modulated sweeps in the inferior colliculus of the pallid bat. J Neurophysiol 2006; 96:1320-36. [PMID: 16790604 DOI: 10.1152/jn.00021.2006] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study describes mechanisms that underlie neuronal selectivity for the direction and rate of frequency-modulated sweeps in the central nucleus of the inferior colliculus (ICC) of the pallid bat (Antrozous pallidus). This ICC contains a high percentage of neurons (66%) that respond selectively to the downward sweep direction of the bat's echolocation pulse. Some (19%) are specialists that respond only to downward sweeps. Most neurons (83%) are also tuned to sweep rates. A two-tone inhibition paradigm was used to describe inhibitory mechanisms that shape selectivity for sweep direction and rate. Two different mechanisms can create similar rate tuning. The first is an early on-best frequency inhibition that shapes duration tuning, which in turn determines rate tuning. In most neurons that are not duration tuned, a delayed high-frequency inhibition creates rate tuning. These neurons respond to fast sweep rates, but are inhibited as rate slows, and delayed inhibition overlaps excitation. In these neurons, starting a downward sweep within the excitatory tuning curve eliminates rate tuning. However, if rate tuning is shaped by duration tuning, this manipulation has no effect. Selectivity for the downward sweep direction is created by an early low-frequency inhibition that prevents responses to upward sweeps. In addition to this asymmetry in arrival times of low- and high-frequency inhibitions, the bandwidth of the low-frequency sideband was broader. Bandwidth influences the arrival time of inhibition during an FM sweep because a broader sideband will be encountered sooner. These findings show that similar spectrotemporal filters can be created by different mechanisms.
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Affiliation(s)
- Zoltan M Fuzessery
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA
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27
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Razak KA, Fuzessery ZM. Neural mechanisms underlying selectivity for the rate and direction of frequency-modulated sweeps in the auditory cortex of the pallid bat. J Neurophysiol 2006; 96:1303-19. [PMID: 16775213 DOI: 10.1152/jn.00020.2006] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Frequency-modulated (FM) sweeps are common in vocalizations, including human speech. Selectivity for FM sweep rate and direction is present in the auditory cortex of many species. The present study sought to determine the mechanisms underlying FM sweep selectivity in the auditory cortex of pallid bats. In the pallid bat inferior colliculus (IC), two mechanisms underlie selectivity for FM sweep rate. The first mechanism depends on duration tuning for tones that arises as a consequence of early inhibition generated by an excitatory tone. The second mechanism depends on a narrow band of delayed high-frequency inhibition. Direction selectivity depends on a broad band of early low-frequency inhibition. Here, the contributions of these mechanisms to cortical FM sweep selectivity were determined in pentobarbital-anesthetized pallid bats. We show that the majority of cortical neurons tuned to echolocation frequencies are selective for the downward direction and rate of FM sweeps. Unlike in IC neurons tuned in the echolocation range, duration tuning is rare in cortical neurons with similar tuning. As in the IC, consistent spectrotemporal differences exist between low- and high-frequency sidebands. A narrow band of delayed high-frequency inhibition is necessary for FM rate selectivity. Low-frequency inhibition has a broad bandwidth, early arrival time, and creates direction selectivity. Cortical neurons respond better to slower FM rates and exhibit broader rate tuning than IC neurons. Relative arrival time of high-frequency inhibition is slower in the cortex than in the IC. Thus whereas similar mechanisms shape direction selectivity of neurons tuned in the echolocation range in the IC and the cortex, only one of the two mechanisms underlying rate selectivity in the IC is present in the cortex.
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Affiliation(s)
- Khaleel A Razak
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA
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28
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Gaese BH, King I, Felsheim C, Ostwald J, von der Behrens W. Discrimination of direction in fast frequency-modulated tones by rats. J Assoc Res Otolaryngol 2006; 7:48-58. [PMID: 16411160 PMCID: PMC2504587 DOI: 10.1007/s10162-005-0022-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Accepted: 11/16/2005] [Indexed: 11/26/2022] Open
Abstract
Fast frequency modulations (FM) are an essential part of species-specific auditory signals in animals as well as in human speech. Major parameters characterizing non-periodic frequency modulations are the direction of frequency change in the FM sweep (upward/downward) and the sweep speed, i.e., the speed of frequency change. While it is well established that both parameters are represented in the mammalian central auditory pathway, their importance at the perceptual level in animals is unclear. We determined the ability of rats to discriminate between upward and downward modulated FM-tones as a function of sweep speed in a two-alternative-forced-choice-paradigm. Directional discrimination in logarithmic FM-sweeps was reduced with increasing sweep speed between 20 and 1,000 octaves/s following a psychometric function. Average threshold sweep speed for FM directional discrimination was 96 octaves/s. This upper limit of perceptual FM discrimination fits well the upper limit of preferred sweep speeds in auditory neurons and the upper limit of neuronal direction selectivity in the rat auditory cortex and midbrain, as it is found in the literature. Influences of additional stimulus parameters on FM discrimination were determined using an adaptive testing-procedure for efficient threshold estimation based on a maximum likelihood approach. Directional discrimination improved with extended FM sweep range between two and five octaves. Discrimination performance declined with increasing lower frequency boundary of FM sweeps, showing an especially strong deterioration when the boundary was raised from 2 to 4 kHz. This deterioration corresponds to a frequency-dependent decline in direction selectivity of FM-encoding neurons in the rat auditory cortex, as described in the literature. Taken together, by investigating directional discrimination of FM sweeps in the rat we found characteristics at the perceptual level that can be related to several aspects of FM encoding in the central auditory pathway.
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Affiliation(s)
- Bernhard H Gaese
- Institut für Biologie II, RWTH Aachen, Kopernikusstr. 16, D-52074, Aachen, Germany.
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29
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Cousillas H, Leppelsack HJ, Leppelsack E, Richard JP, Mathelier M, Hausberger M. Functional organization of the forebrain auditory centres of the European starling: a study based on natural sounds. Hear Res 2006; 207:10-21. [PMID: 15996840 DOI: 10.1016/j.heares.2005.01.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2002] [Accepted: 01/10/2005] [Indexed: 10/25/2022]
Abstract
The field L complex is thought to be the highest auditory centre and the input in the song vocal nuclei. Different anatomical and functional subdivisions have been described in field L. Auditory neurons of field L are well activated by natural sounds and especially by species-specific sounds. A complex sound coding appears to exist in field L. However, until now, the spatial organization of the different functional subdivisions has been described only using artificial sounds. Here, we investigated the spatial distribution of neuronal responses in field L to species-specific songs. Starlings seemed to be a very appropriate species for this investigation, both because of their complex vocal behaviour that implies different levels of categorization and their neuronal responses towards complex song elements. Multi-unit recordings were performed in wild starlings that were awake. The method of backward correlation was used to visualize the functional organization and we represented the neuronal responses as both activity maps and correlation maps. The use of natural sounds allowed us to define several functional sub-areas with different neuronal processing. These results show that field L is involved in a more complex task than simple frequency processing.
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Affiliation(s)
- H Cousillas
- UMR 6552 CNRS, Ethologie-Evolution-Ecologie, Université de Rennes 1, 263, Avenue du Général Leclerc, 35042 Rennes Cedex, France.
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30
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Metherate R, Kaur S, Kawai H, Lazar R, Liang K, Rose HJ. Spectral integration in auditory cortex: mechanisms and modulation. Hear Res 2005; 206:146-58. [PMID: 16081005 DOI: 10.1016/j.heares.2005.01.014] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2004] [Accepted: 01/06/2005] [Indexed: 11/19/2022]
Abstract
Auditory cortex contributes to the processing and perception of spectrotemporally complex stimuli. However, the mechanisms by which this is accomplished are not well understood. In this review, we examine evidence that single cortical neurons receive input covering much of the audible spectrum. We then propose an anatomical framework by which spectral information converges on single neurons in primary auditory cortex, via a combination of thalamocortical and intracortical "horizontal" pathways. By its nature, the framework confers sensitivity to specific, spectrotemporally complex stimuli. Finally, to address how spectral integration can be regulated, we show how one neuromodulator, acetylcholine, could act within the hypothesized framework to alter integration in single neurons. The results of these studies promote a cellular understanding of information processing in auditory cortex.
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Affiliation(s)
- Raju Metherate
- Department of Neurobiology and Behavior, University of California, Irvine, 2205 McGaugh Hall, Irvine, CA 92697-4550, United States.
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31
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Brimijoin WO, O’Neill WE. On the prediction of sweep rate and directional selectivity for FM sounds from two-tone interactions in the inferior colliculus. Hear Res 2005; 210:63-79. [PMID: 16263230 PMCID: PMC3901414 DOI: 10.1016/j.heares.2005.07.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2005] [Accepted: 07/08/2005] [Indexed: 11/30/2022]
Abstract
Two-tone stimuli have traditionally been used to reveal regions of inhibition in auditory spectral receptive fields, particularly for neurons with low spontaneous rates. These techniques reveal how different frequencies excite or suppress the response to an excitatory frequency of a cell, but have often been assessed at a fixed masker-probe time interval. We used a variation of this methodology to determine whether two-tone spectrotemporal interactions can account for rate-dependent directional selectivity for frequency modulations (FM) in the mustached bat inferior colliculus (IC). First, we quantified the response to upward and downward sweeping, linear, fixed-bandwidth FM tones centered at a unit's characteristic frequency (CF) at 6 sweep durations ranging from 2 to 64 ms. Then, to examine how responses to instantaneous frequencies contained within the sweeps might interact in time, we varied the frequency and relative onset of a brief (4 ms) "conditioner" tone paired with a fixed 4-ms CF probe tone. We constructed "conditioned response areas" (CRA) depicting regions of suppression and facilitation of the probe tone caused by the conditioning tone. We classified the CRAs as predominantly excitatory (40.9%), inhibitory (22.7%), or mixed (36.4%). To generate FM response predictions, the CRAs were multiplied with spectrograms of the same sweeps used to assess response to FM. The predictions of FM rate and directionality were accurate by our criteria in approximately 20% of units. Conversely, the CRAs from the remaining units failed to predict FM responses as accurately, suggesting that most IC units respond differently to FM sweeps than they do to tone-pairs matched to the instantaneous frequencies contained in those sweeps. The implications of these results for models of FM directionality are discussed.
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Affiliation(s)
- W. Owen Brimijoin
- Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY 14627, USA
| | - William E. O’Neill
- Center for Navigation and Communication Sciences, 601 Elmwood Avenue, Rochester, NY 14642-8603, USA
- Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY 14627, USA
- Department of Neurobiology & Anatomy, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642-8603, USA
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George I, Cousillas H, Vernier B, Richard JP, Henry L, Mathelier M, Lengagne T, Hausberger M. Sound processing in the auditory-cortex homologue of songbirds: functional organization and developmental issues. ACTA ACUST UNITED AC 2005; 98:385-94. [PMID: 16293403 DOI: 10.1016/j.jphysparis.2005.09.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Recent literature on the Field L of songbirds, showing that some neurons present a clear selectivity towards complex sounds, especially conspecific songs, is reviewed. Furthermore, studies on European starlings have revealed a complex functional organization in this central auditory area, with subareas exhibiting different response features. Interestingly, both the functional organization and the neuronal specialization can be drastically affected by early deprivation, clearly showing the existence of a developmental plasticity. Some recovery seems to remain possible at later stages, and social factors may be involved.
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Affiliation(s)
- I George
- UMR CNRS 6552, Université Rennes 1, Campus de Beaulieu, France
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33
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Godey B, Atencio CA, Bonham BH, Schreiner CE, Cheung SW. Functional Organization of Squirrel Monkey Primary Auditory Cortex: Responses to Frequency-Modulation Sweeps. J Neurophysiol 2005; 94:1299-311. [PMID: 16061492 DOI: 10.1152/jn.00950.2004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The squirrel monkey twitter call is an exemplar of a broad class of species-specific vocalizations that contain naturally voiced frequency-modulated (FM) sweeps. To investigate how this prominent communication call element is represented in primary auditory cortex (AI), neuronal receptive field properties to pure-tone and synthetic, logarithmically spaced FM-sweep stimuli in 3 barbiturate-anesthetized squirrel monkeys are studied. Responses to pure tones are assessed by using standard measures of frequency response areas, whereas responses to FM sweeps are classified according to direction selectivity, best speed, and speed tuning preferences. Most neuronal clusters respond to FM sweeps in both directions and over a range of FM speeds. Center frequencies calculated from the average of high and low trigger frequency edges of FM response profiles are highly correlated with pure-tone characteristic frequencies (CFs). However, bandwidth estimates are only weakly correlated with their pure-tone counterparts. CF and direction selectivity are negatively correlated. Best speed maps reveal idiosyncratically positioned spatial aggregation of similar values. In contrast, direction selectivity maps show unambiguous spatial organization. Neuronal clusters selective for upward-directed FM sweeps are located in ventral–caudal AI, where CFs range from 0.5 to 1 kHz. Combinations of pure-tone and FM response parameters form 2 significant factors to account for response variations. These results are interpreted in the context of earlier FM investigations and neuronal encoding of dynamic sounds.
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Affiliation(s)
- Benoit Godey
- Laboratoire IDM, UPRES-EA 3192, Université de Rennes 1, Rennes, France
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34
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Cousillas H, Richard JP, Mathelier M, Henry L, George I, Hausberger M. Experience-dependent neuronal specialization and functional organization in the central auditory area of a songbird. Eur J Neurosci 2004; 19:3343-52. [PMID: 15217389 DOI: 10.1111/j.0953-816x.2004.03376.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The effect of early experience on brain development was investigated in the central auditory area of a songbird, the field L complex, which is analogous to the mammalian auditory cortex. Multi-unit recordings of auditory responses in the field L complex of adult starlings raised without any experience of adult song during development provide strong evidence of developmental plasticity both in the neuronal responses and in the functional organization of this area. Across the entire area, experimental birds, separated from adults from the age of 1 week old until they were 2 years old, had a much larger number of neurons that responded to all the stimuli than did control birds. The well-known tonotopy demonstrated in adult wild birds using the same procedure was altered. This study is the first to bring evidence of developmental plasticity in the organization of the central auditory areas in songbirds. These results are discussed in relation to other reports on effects of early experience on brain development.
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Affiliation(s)
- Hugo Cousillas
- UMR 6552 CNRS, Ethologie-Evolution-Ecologie, Université de Rennes 1, Campus de Beaulieu, 263, Avenue du Général Leclerc, 35042 Rennes Cedex, France.
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35
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George I, Vernier B, Richard JP, Hausberger M, Cousillas H. Hemispheric specialization in the primary auditory area of awake and anesthetized starlings (Sturnus vulgaris). Behav Neurosci 2004; 118:597-610. [PMID: 15174938 DOI: 10.1037/0735-7044.118.3.597] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although evidence exists for a lateralization of song production, few studies have focused on the perceptual aspect of lateralization in songbirds. In the present study, the authors recorded neuronal responses to a variety of species-specific and artificial, nonspecific stimuli in both hemispheres of awake and anesthetized male starlings (Sturnus vulgaris). Recordings were made in the primary auditory area of the songbird brain, the Field L complex. The right hemisphere exhibited significantly more responsive units than the left hemisphere in awake birds, and this difference was significantly reduced in anesthetized birds. Furthermore, clear hemispheric specialization toward categories of behaviorally relevant stimuli and precise parameters of these stimuli were found. The main auditory area of the starling's brain thus appears to show some degree of lateralization.
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Affiliation(s)
- Isabella George
- Unite Mixte de Recherche 6552, Ethologie-Evolution-Ecologie, Centre National de la Recherche Scientifique and Universitee Rennes 1, Campus de Beaulieu, Bâtiment 25, 35042 Rennes Cedex, France.
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Kaur S, Lazar R, Metherate R. Intracortical Pathways Determine Breadth of Subthreshold Frequency Receptive Fields in Primary Auditory Cortex. J Neurophysiol 2004; 91:2551-67. [PMID: 14749307 DOI: 10.1152/jn.01121.2003] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To examine the basis of frequency receptive fields in auditory cortex (ACx), we have recorded intracellular (whole cell) and extracellular (local field potential, LFP) responses to tones in anesthetized rats. Frequency receptive fields derived from excitatory postsynaptic potentials (EPSPs) and LFPs from the same location resembled each other in terms of characteristic frequency (CF) and breadth of tuning, suggesting that LFPs reflect local synaptic (including subthreshold) activity. Subthreshold EPSP and LFP receptive fields were remarkably broad, often spanning five octaves (the maximum tested) at moderate intensities (40–50 dB above threshold). To identify receptive-field features that are generated intracortically, we microinjected the GABAA receptor agonist muscimol (0.2–5.1 mM, 1–5 μl) into ACx. Muscimol dramatically reduced LFP amplitude and reduced receptive-field bandwidth, implicating intracortical contributions to these features but had lesser effects on CF response threshold or onset latency, suggesting minimal loss of thalamocortical input. Reversal of muscimol's inhibition preferentially at the recording site by diffusion from the recording pipette of the GABAA receptor antagonist picrotoxin (0.01–100 μM) disinhibited responses to CF stimuli more than responses to spectrally distant, non-CF stimuli. We propose that thalamocortical and intracortical pathways preferentially contribute to responses evoked by CF and non-CF stimuli, respectively, and that intracortical projections linking frequency representations determine the breadth of receptive fields in primary ACx. Broad, subthreshold receptive fields may distinguish ACx from subcortical auditory relay nuclei, promote integrated responses to spectrotemporally complex stimuli, and provide a substrate for plasticity of cortical receptive fields and maps.
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Affiliation(s)
- Simranjit Kaur
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA
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Weisz N, Wienbruch C, Hoffmeister S, Elbert T. Tonotopic organization of the human auditory cortex probed with frequency-modulated tones. Hear Res 2004; 191:49-58. [PMID: 15109704 DOI: 10.1016/j.heares.2004.01.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2003] [Accepted: 01/09/2004] [Indexed: 11/25/2022]
Abstract
Using neuromagnetic source imaging, we investigated tonotopic representation and direction sensitivity in the auditory cortex of humans (N = 15). For this purpose, source analysis was undertaken at every single sampling point during the presentation of a frequency-modulated tone (FM) sweeping slowly downward or upward across periods of 3 s duration. Stimuli were selected to target response properties of the central part of the primary auditory cortical field, which has been shown to exhibit sensitivity to distinct FM-sound features as compared to the ventral and dorsal part. Linear mixed-effects model statistics confirm tonotopic gradients in medial-lateral and anterior-posterior directions. The high resolution provided by this method revealed that the relationship between frequency and spatial location of the responding neural tissue is nonlinear. The idea that neurons specifically sensitive to the employed sound characteristics (slow, downward modulation) were activated is supported by the fact that the upward sweep of identical duration produced a different pattern of functional organisation.
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Affiliation(s)
- Nathan Weisz
- Department of Psychology, University of Konstanz, Box D25, 78457 Konstanz, Germany.
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Fishbach A, Yeshurun Y, Nelken I. Neural model for physiological responses to frequency and amplitude transitions uncovers topographical order in the auditory cortex. J Neurophysiol 2003; 90:3663-78. [PMID: 12944531 DOI: 10.1152/jn.00654.2003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We characterize primary auditory cortex (AI) units using a neural model for the detection of frequency and amplitude transitions. The model is a generalization of a model for the detection of amplitude transition. A set of neurons, tuned in the spectrotemporal domain, is created by means of neural delays and frequency filtering. The sensitivity of the model to frequency and amplitude transitions is achieved by applying a 2-dimensional rotatable receptive field to the set of spectrotemporally tuned neurons. We evaluated the model using data recorded in AI of anesthetized ferrets. We show that the model is able to fit the responses of AI units to variety of stimuli, including single tones, delayed 2-tone stimuli and various frequency-modulated tones, using only a small number of parameters. Furthermore, we show that the topographical order in maps of the model parameters is higher than in maps created from response indices extracted directly from the responses to any single stimulus. These results suggest a possible ordered organization of a simple rotatable spectrotemporal receptive field in the mammalian AI.
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Affiliation(s)
- Alon Fishbach
- Department of Physiology, Northwestern University, Chicago, Illinois 60611, USA.
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Abstract
ON and OFF auditory responses were examined in the medial geniculate body (MGB) of the guinea pig. Single- and multiunit recordings were carried out on 12 anesthetized animals, and noise-burst or pure-tone stimuli were applied to the ear contralateral to the recording hemisphere. One hundred and thirty-five OFF or ON-OFF neurons and 160 ON neurons were studied, and the tuning curves of 21 ON-OFF or OFF neurons were examined from various nuclei of the MGB. The mean minimum threshold of the OFF responses (40.8 +/- 20.0 dB SPL, mean +/- SD; range: 0-80 dB SPL) was significantly higher than that of the ON responses (28.5 +/- 17.6 dB SPL, range: 0-60 dB SPL; n = 17, P < 0.001). Of 10 ON-OFF neurons that showed identifiable tuning frequencies for both ON and OFF responses, 7 showed a higher OFF than ON best frequency (BF), 2 showed the same BF for both ON and OFF, and only 1 showed a slightly lower OFF than ON BF. Most OFF responses sampled from the borders of the ventral (MGv) and the rostromedial (MGrm) nuclei of the MGB showed single-peaked tuning curves, similar to those of the ON responses in the MGv. The neurons located in the shell (MGs) and dorsal (MGd) nuclei of the MGB showed complicated-either multi-peaked or broad-tuning curves. All OFF responses showed long-duration-selectivity for acoustic stimuli: the mean half-maximum duration was 116.5 +/- 114.8 ms (n = 19, range: 27-411 ms). The latencies of 135 OFF responses were studied in various divisions of the MGB. The ventral border region of MGv showed the shortest latency, followed by the dorsal border region of the MGv, the MGrm, and the caudomedial nucleus (MGcm) of the MGB. The posterior nucleus of the thalamus (Po), the MGd, and the MGs showed much longer mean latencies of >30 ms (P < 0.05 compared with the border regions of the MGv, ANOVA), with Po showing the greatest mean latency of 60.3 ms and the greatest deviation of 25.5 ms). The latency of the OFF response (29.0 +/- 14.0 ms, n = 135) was significantly greater than that of the ON response (15.6 +/- 9.6 ms, n = 160, P < 0.001). The present results provide valuable information about the threshold, frequency tuning characteristics, minimal response latency, and duration selectivity of OFF neurons in the auditory thalamus.
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Affiliation(s)
- Jufang He
- Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China. rsjufang!polyu.edu.hk
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O'Neill WE, Brimijoin WO. Directional selectivity for FM sweeps in the suprageniculate nucleus of the mustached bat medial geniculate body. J Neurophysiol 2002; 88:172-87. [PMID: 12091543 PMCID: PMC3904363 DOI: 10.1152/jn.00966.2001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mustached bats emit echolocation and communication calls containing both constant frequency (CF) and frequency-modulated (FM) components. Previously we found that 86% of neurons in the ventral division of the external nucleus of the inferior colliculus (ICXv) were directionally selective for linear FM sweeps and that selectivity was dependent on sweep rate. The ICXv projects to the suprageniculate nucleus (Sg) of the medial geniculate body. In this study, we isolated 37 single units in the Sg and measured their responses to best excitatory frequency (BEF) tones and linear 12-kHz upward and downward FM sweeps centered on the BEF. Sweeps were presented at durations of 30, 12, and 4 ms, yielding modulation rates of 400, 1,000, and 3,000 kHz/s. Spike count versus level functions were obtained at each modulation rate and compared with BEF controls. Sg units responded well to both tones and FM sweeps. BEFs clustered at 58 kHz, corresponding to the dominant CF component of the sonar signal. Spike count functions for both tones and sweeps were predominantly non-monotonic. FM directional selectivity was significant in 53-78% of the units, depending on modulation rate and level. Units were classified as up-selective (52%), down-selective (24%), or bi-directional (non-selective, 16%); a few units (8%) showed preferences that were either rate- or level-dependent. Most units showed consistent directional preferences at all SPLs and modulation rates tested, but typically showed stronger selectivity at lower sweep rates. Directional preferences were attributable to suppression of activity by sweeps in the non-preferred direction (~80% of units) and/or facilitation by sweeps in the preferred direction (~20-30%). Latencies for BEF tones ranged from 4.9 to 25.7 ms. Latencies for FM sweeps typically varied linearly with sweep duration. Most FM latency-duration functions had slopes ranging from 0.4 to 0.6, suggesting that the responses were triggered by the BEF. Latencies for BEF tones and FM sweeps were significantly correlated in most Sg units, i.e., the response to FM was temporally related to the occurrence of the BEF in the FM sweep. FM latency declined relative to BEF latency as modulation rate increased, suggesting that at higher rates response is triggered by frequencies in the sweep preceding the BEF. We conclude that Sg and ICXv units have similar, though not identical, response properties. Sg units are predominantly upsweep selective and could respond to either or both the CF and FM components in biosonar signals in a number of echolocation scenarios, as well as to a variety of communication sounds.
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Affiliation(s)
- William E O'Neill
- Department of Neurobiology and Anatomy, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642-8603, USA.
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41
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Abstract
ON and OFF auditory responses were examined on the medial geniculate body (MGB) of the guinea pig. Single-unit and multiunit recordings were performed on 13 anesthetized subjects while either noise-burst or pure-tone stimuli were applied to the ear contralateral to the recorded hemisphere. Of 2187 uneven-spaced samples, 1142 were ON neurons, 386 were OFF neurons, and 488 were ON-OFF neurons. Neither ON nor OFF neurons changed their response patterns when the stimulus was changed from a noise burst of 60 dB sound pressure level intensity (expressed in decibels per 20 mPa) to pure tones or noise bursts of other intensities. However, most of the ON-OFF neurons changed to either ON or OFF responses with some stimuli. OFF neurons formed clusters. With anatomical confirmation, we found that OFF neuron clusters are always segregated from ON neuron clusters and form OFF sheets in various divisions of the MGB. In the ventral division of the MGB (MGv), the neurons showed mainly ON responses in its core and OFF responses in its periphery or on its boundary with other divisions. The MGv was partially surrounded by an OFF sheet dorsolaterally at the caudal part and medioventrally at the rostral part and was almost completely surrounded by an OFF sheet at the central level rostrocaudally.
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Abstract
Studies in several mammalian species have demonstrated that auditory cortical neurons respond strongly to single frequency-modulated (FM) sweeps, and that most responses are selective for sweep direction and/or rate. In the present study, we used extracellular recordings to examine how neurons in the auditory cortices of anesthetized rats respond to continuous, periodic trains of FM sweeps (described previously by deCharms et al., Science 280 (1998) pp. 1439-1444, as moving auditory gratings). Consistent with previous observations in owl monkeys, we found that the majority of cortical neurons responded selectively to trains of either up-sweeps or down-sweeps; selectivity for down-sweeps was most common. Periodic responses were typically evoked only by sweep trains with repetition rates less than 12 sweeps per second. Directional differences in responses were dependent on repetition rate. Our results support the proposal that a combination of both spectral and temporal acoustic features determines the responses of auditory cortical neurons to sound, and add to the growing body of evidence indicating that the traditional view of the auditory cortex as a frequency analyzer is not sufficient to explain how the mammalian brain represents complex sounds.
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Affiliation(s)
- I Orduña
- Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, NJ 07102, USA.
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43
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Nieder A, Klump GM. Signal detection in amplitude-modulated maskers. II. Processing in the songbird's auditory forebrain. Eur J Neurosci 2001; 13:1033-44. [PMID: 11264677 DOI: 10.1046/j.0953-816x.2001.01465.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the natural environment, acoustic signals have to be detected in ubiquitous background noise. Temporal fluctuations of background noise can be exploited by the auditory system to enhance signal detection, especially if spectral masking components are coherently amplitude modulated across several auditory channels (a phenomenon called 'comodulation masking release'). In this study of neuronal mechanisms of masking release in the primary auditory forebrain (field L) of awake European starlings (Sturnus vulgaris), we determined and compared neural detection thresholds for 20-ms probe tones presented in a background of sinusoidally amplitude modulated (10-Hz) noise maskers. Responses of a total of 34 multiunit clusters were recorded via radiotelemetry with chronically implanted microelectrodes from unrestrained birds. For maskers consisting of a single noise band centred around the recording site's characteristic frequency, a substantial reduction in detection threshold (21 dB on average) was found when probe tones were presented during envelope dips rather than during envelope peaks. Such effects could also explain results obtained for masking protocols where the on-frequency noise band was presented together with excitatory or inhibitory flanking bands that were either coherently modulated (in-phase) or incoherently modulated (phase-shifted). Generally, masking release for probe tones in maskers with flanking bands extending beyond the frequency range of a cell cluster's excitatory tuning curve was not substantially improved. Only some of the neurophysiological results are in agreement with behavioural data from the same species if only the average population response is considered. A subsample of individual neurons, however, could account for behavioural thresholds.
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Affiliation(s)
- A Nieder
- Institut für Zoologie, Technische Universtät München, Lichtenbergstr. 4, D-85747 Garching, Germany
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44
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Gehr DD, Hofer SB, Marquardt D, Leppelsack H. Functional changes in field L complex during song development of juvenile male zebra finches. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2000; 125:153-65. [PMID: 11154771 DOI: 10.1016/s0165-3806(00)00131-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The field L complex is the highest station of the ascending auditory pathway and is thought to be the input stage of auditory information into the song system in birds. Multi-unit recordings were performed in awake, socially reared zebra finches, 30 and 60 days of age. The responses of the field L complex to synthetic and natural stimuli during important periods of song learning were investigated. According to neural responses in field L, three different functional areas could be distinguished, NA-L(30), NA2b(30) and NA2c(30,) in 30 days old birds. In 60 days old birds five different functional areas, NA-L(60), NA2a(60), NA2b(60), NA2c(60) and NA3(60), were recognised. Especially, NA-L increases its functional volume between the developmental stages. The different areas showed already mature neuronal response behaviours. No preference for a certain song type could be found at all ages. The incomplete functional organisation of the field L complex in young birds (30 days) is a possible reason for the nonselectivity in the song system at this age.
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Affiliation(s)
- D D Gehr
- Institute of Zoology, Technical University of Munich, Lichtenbergstrasse 4, 85747, Garching, Germany
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45
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Gordon M, O'Neill WE. An extralemniscal component of the mustached bat inferior colliculus selective for direction and rate of linear frequency modulations. J Comp Neurol 2000; 426:165-81. [PMID: 10982461 PMCID: PMC3940212 DOI: 10.1002/1096-9861(20001016)426:2<165::aid-cne1>3.0.co;2-i] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Frequency modulations (FMs) are prevalent in human speech, and are important acoustic cues for the categorical discrimination of phonetic contrasts. For bats, FM sweeps are also important for communication and are often the only component in echolocation calls. Auditory neurons tuned to the direction and rate of FM might underlie the encoding of rapid frequency transitions. In the mustached bat, we have discovered a population of such FM selective cells in an area interposed between the central nucleus of the inferior colliculus (ICC) and the nuclei of the lateral lemniscus (NLL). We believe this area to be the ventral extent of the external nucleus of the inferior colliculus (ICXv). To describe FM selectivity of neurons in the ICXv and to compare it to other midbrain nuclei, up- and down-sweeping linear FM stimuli were presented at different modulation rates. Extracellular recordings were made from 171 single units in the ICC, ICXv, and NLL of 10 mustached bats. In the ICXv, there was a much higher degree of FM selectivity than in ICC or NLL and a consistent preference for upward over downward FM sweeps. Anterograde and retrograde transport was examined following focal injections of wheatgerm agglutinin-horseradish peroxidase (WGA-HRP) into ICXv. The main targets of anterograde transport were the deep layers of the superior colliculus and the suprageniculate division of the medial geniculate body. The primary site of retrograde transport was the nucleus of the central acoustic tract in the brainstem. Thus, the ICXv appears to be a part of the central acoustic tract, an extralemniscal pathway linking the auditory brainstem directly to a multimodal nucleus of the thalamus.
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Affiliation(s)
- M Gordon
- Program in Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
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46
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Ohl FW, Schulze H, Scheich H, Freeman WJ. Spatial representation of frequency-modulated tones in gerbil auditory cortex revealed by epidural electrocorticography. JOURNAL OF PHYSIOLOGY, PARIS 2000; 94:549-54. [PMID: 11165919 DOI: 10.1016/s0928-4257(00)01091-3] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The present study investigated the topography of epidurally recorded middle latency components P1 and N1 evoked by spectrally dynamic stimuli (linearly frequency-modulated (FM) tones) with respect to the tonotopic structure of the right primary auditory cortex, field AI. Whereas the gross topography corresponded to the spectral content of the FM tones, specific tonotopic offsets were found between the potential distributions evoked by FM tones of different modulation direction (i.e. 'rising' vs. 'falling'). Potentials evoked by rising FM tones were located at tonotopic positions corresponding to higher frequencies compared with potentials evoked by falling FM tones. Data indicated that the magnitude of these offsets can be attributed to the local tonotopic resolution in AI and are not dependent on the modulation rate.
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Affiliation(s)
- F W Ohl
- Department of Molecular & Cell Biology, Division of Neurobiology, Life Science Addition 129, University of California, Berkeley, CA 94720, USA.
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47
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Sanderson MI, Simmons JA. Neural responses to overlapping FM sounds in the inferior colliculus of echolocating bats. J Neurophysiol 2000; 83:1840-55. [PMID: 10758096 DOI: 10.1152/jn.2000.83.4.1840] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The big brown bat, Eptesicus fuscus, navigates and hunts prey with echolocation, a modality that uses the temporal and spectral differences between vocalizations and echoes from objects to build spatial images. Closely spaced surfaces ("glints") return overlapping echoes if two echoes return within the integration time of the cochlea ( approximately 300-400 micros). The overlap results in spectral interference that provides information about target structure or texture. Previous studies have shown that two acoustic events separated in time by less than approximately 500 micros evoke only a single response from neural elements in the auditory brain stem. How does the auditory system encode multiple echoes in time when only a single response is available? We presented paired FM stimuli with delay separations from 0 to 24 micros to big brown bats and recorded local field potentials (LFPs) and single-unit responses from the inferior colliculus (IC). These stimuli have one or two interference notches positioned in their spectrum as a function of two-glint separation. For the majority of single units, response counts decreased for two-glint separations when the resulting FM signal had a spectral notch positioned at the cell's best frequency (BF). The smallest two-glint separation that reliably evoked a decrease in spike count was 6 micros. In addition, first-spike latency increased for two-glint stimuli with notches positioned nearby BF. The N(4) potential of averaged LFPs showed a decrease in amplitude for two-glint separations that had a spectral notch near the BF of the recording site. Derived LFPs were computed by subtracting a common-mode signal from each LFP evoked by the two-glint FM stimuli. The derived LFP records show clear changes in both the amplitude and latency as a function of two-glint separation. These observations in relation with the single-unit data suggest that both response amplitude and latency can carry information about two-glint separation in the auditory system of E. fuscus.
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Affiliation(s)
- M I Sanderson
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912, USA
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Capsius B, Leppelsack H. Response patterns and their relationship to frequency analysis in auditory forebrain centers of a songbird. Hear Res 1999; 136:91-9. [PMID: 10511628 DOI: 10.1016/s0378-5955(99)00112-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In the field L complex, the auditory part of the caudal telencephalon, multi-unit recordings were performed in seven awake, adult male starlings (Sturnus vulgaris, L). Pure tones in a frequency range between 0.5 and 6.0 kHz were used as stimuli. The field L complex of starlings consists of at least 11 functionally separated, tonotopically organized subcenters. The auditory processing of frequency information was investigated in eight of these areas. Two kinds of response patterns could be distinguished. The centers NA-L, NA2a, NA3 and NA4 showed phasic and sustained excitation, the other areas responded with phasic excitation only. All these auditory areas show strong tonotopic gradients, each of them representing the complete hearing range. The sharpest picture of the stimulus frequency is represented in the functional area NA-L. In relation to its total size, NA-L shows the smallest active area if stimulated by pure tones. In addition, in NA-L, only the excited neurons are surrounded by inhibited neurons during the response to a pure tone. This leads to an additional sharpening of frequency representation. In comparison with the other auditory areas, NA-L shows the greatest spatial extension of the tonotopic gradient. This, in combination with the smallest active size in NA-L, leads to the conclusion that in the primary projection field NA-L, the most neural space is available for the processing of a given frequency range.
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Affiliation(s)
- B Capsius
- Institut für Zoologie, Technischen Universität München, Lichtenbergstr. 4, 85747, Garching, Germany
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49
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Gordon M, O'Neill WE. Temporal processing across frequency channels by FM selective auditory neurons can account for FM rate selectivity. Hear Res 1998; 122:97-108. [PMID: 9714578 DOI: 10.1016/s0378-5955(98)00087-2] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Auditory neurons tuned to the direction and rate of frequency modulations (FM) might underlie the encoding of frequency sweeps in animal vocalizations and formant transitions in human speech. We examined the relationship between FM direction and rate selectivity and the precise temporal interactions of excitatory and inhibitory sideband inputs. Extracellular single-unit recordings were made in the auditory midbrains of eight mustached bats. Up- and down-sweeping linear FM stimuli were presented at different modulation rates in order to determine FM selectivity. Brief tone pairs with varying interstimulus delays were presented in a forward masking paradigm to examine the relative timing of excitatory and inhibitory inputs. In the 33 units for which tone pair data were collected, a correspondence existed between FM rate selectivity and the time delays between paired tones. Moreover, FM directional selectivity was strongly linked to rate selectivity, because directional preferences were expressed only at certain rates and not others. We discuss how abnormalities in the relative timing of inputs could alter or abolish the selectivity of such neurons, and how such a mechanism could account for the perceptual deficits for formant transitions seen in certain children with phonological deficits.
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Affiliation(s)
- M Gordon
- Program in Neuroscience, University of Rochester School of Medicine and Dentistry, NY 14642, USA
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50
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Heil P, Irvine DR. Functional specialization in auditory cortex: responses to frequency-modulated stimuli in the cat's posterior auditory field. J Neurophysiol 1998; 79:3041-59. [PMID: 9636107 DOI: 10.1152/jn.1998.79.6.3041] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The mammalian auditory cortex contains multiple fields but their functional role is poorly understood. Here we examine the responses of single neurons in the posterior auditory field (P) of barbiturate- and ketamine-anesthetized cats to frequency-modulated (FM) sweeps. FM sweeps traversed the excitatory response area of the neuron under study, and FM direction and the linear rate of change of frequency (RCF) were varied systematically. In some neurons, sweeps of different sound pressure levels (SPLs) also were tested. The response magnitude (number of spikes corrected for spontaneous activity) of nearly all field P neurons varied with RCF. RCF response functions displayed a variety of shapes, but most functions were of low-pass characteristic or peaked at rather low RCFs (<100 kHz/s). Neurons with strong responses to high RCFs (high-pass or nonselective RCF response function characteristics) all displayed spike count-SPL functions to tone burst onsets that were monotonic or weakly nonmonotonic. RCF response functions and best RCFs often changed with SPL. For most neurons, FM directional sensitivity, quantified by a directional sensitivity (DS) index, also varied with RCF and SPL, but the mean and width of the distribution of DS indices across all neurons was independent of RCF. Analysis of response timing revealed that the phasic response of a neuron is triggered when the instantaneous frequency of the sweep reaches a particular value, the effective Fi. For a given neuron, values of effective Fi were independent of RCF, but depended on FM direction and SPL and were associated closely with the boundaries of the neuron's frequency versus amplitude response area. The standard deviation (SD) of the latency of the first spike of the response decreased with RCF. When SD was expressed relative to the rate of change of stimulus frequency, the resulting index of frequency jitter increased with RCF and did so rather uniformly in all neurons and largely independent of SPL. These properties suggest that many FM parameters are represented by, and may be encoded in, orderly temporal patterns across different neurons in addition to the strength of responses. When compared with neurons in primary and anterior auditory fields, field P neurons respond better to relatively slow FMs. Together with previous studies of responses to modulations of amplitude, such as tone onsets, our findings suggest more generally that field P may be best suited for processing signals that vary relatively slowly over time.
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Affiliation(s)
- P Heil
- Department of Psychology, Monash University, Clayton, Victoria 3168, Australia
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