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Singh R, Bharadwaj HM. Cortical temporal integration can account for limits of temporal perception: investigations in the binaural system. Commun Biol 2023; 6:981. [PMID: 37752215 PMCID: PMC10522716 DOI: 10.1038/s42003-023-05361-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 09/15/2023] [Indexed: 09/28/2023] Open
Abstract
The auditory system has exquisite temporal coding in the periphery which is transformed into a rate-based code in central auditory structures, like auditory cortex. However, the cortex is still able to synchronize, albeit at lower modulation rates, to acoustic fluctuations. The perceptual significance of this cortical synchronization is unknown. We estimated physiological synchronization limits of cortex (in humans with electroencephalography) and brainstem neurons (in chinchillas) to dynamic binaural cues using a novel system-identification technique, along with parallel perceptual measurements. We find that cortex can synchronize to dynamic binaural cues up to approximately 10 Hz, which aligns well with our measured limits of perceiving dynamic spatial information and utilizing dynamic binaural cues for spatial unmasking, i.e. measures of binaural sluggishness. We also find that the tracking limit for frequency modulation (FM) is similar to the limit for spatial tracking, demonstrating that this sluggish tracking is a more general perceptual limit that can be accounted for by cortical temporal integration limits.
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Affiliation(s)
- Ravinderjit Singh
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Hari M Bharadwaj
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, IN, USA.
- Department of Communication Science and Disorders, University of Pittsburgh, Pittsburgh, PA, USA.
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Xu N, Luo L, Chen L, Ding Y, Li L. Different binaural processing of the envelope component and the temporal fine structure component of a narrowband noise in rat inferior colliculus. Hear Res 2021; 411:108354. [PMID: 34583218 DOI: 10.1016/j.heares.2021.108354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 08/29/2021] [Accepted: 09/15/2021] [Indexed: 11/18/2022]
Abstract
Complex broadband sounds are decomposed by peripheral auditory filters into a series of relatively narrowband signals, each with a slowly varying envelope (ENV) and a rapidly fluctuating temporal fine structure (TFS). ENV and TFS information at the bilateral ears contribute differentially to auditory perception. However, whether the difference could attribute to mechanisms of binaural integration remains an open question. As a potential neural correlate, subsets of neurons in the central nucleus of the inferior colliculus (ICC) are known to integrate binaural information with binaural inhibition or binaural summation. Therefore, we recorded the frequency-following responses (FFRs) to the ENV and TFS components of narrowband noises in the ICC of anesthetized rats and examined changes in FFR amplitude and stimulus-response coherence under various sound-delivery settings. We showed that binaural FFRENV was predominantly elicited by contralateral inputs and inhibited by ipsilateral inputs, exhibiting a "binaural-inhibition" like property. On the other hand, binaural FFRTFS received a balanced contribution from both sides, echoing the "binaural-summation" mechanism. What is more, binaural FFRENV was significantly correlated with contralateral-evoked but not ipsilateral-evoked FFRENV, while binaural FFRTFS correlated with both contralateral- and ipsilateral-evoked FFRTFS. Overall, these results suggest distinct binaural processing of ENV and TFS information at the midbrain level.
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Affiliation(s)
- Na Xu
- School of Psychological and Cognitive Sciences, Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100080, China; Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China.
| | - Lu Luo
- School of Psychological and Cognitive Sciences, Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100080, China; School of Psychology, Beijing Sport University, Beijing 100084, China
| | - Liangjie Chen
- School of Psychological and Cognitive Sciences, Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100080, China
| | - Yu Ding
- School of Psychological and Cognitive Sciences, Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100080, China; Division of Sports Science and physical education, Tsinghua University, Beijing 100084, China
| | - Liang Li
- School of Psychological and Cognitive Sciences, Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100080, China; Speech and Hearing Research Center, Key Laboratory on Machine Perception (Ministry of Education), Peking University, Beijing 100871, China; Beijing Institute for Brain Disorders, Beijing 100096, China.
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Zuk NJ, Delgutte B. Neural coding and perception of auditory motion direction based on interaural time differences. J Neurophysiol 2019; 122:1821-1842. [PMID: 31461376 DOI: 10.1152/jn.00081.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
While motion is important for parsing a complex auditory scene into perceptual objects, how it is encoded in the auditory system is unclear. Perceptual studies suggest that the ability to identify the direction of motion is limited by the duration of the moving sound, yet we can detect changes in interaural differences at even shorter durations. To understand the source of these distinct temporal limits, we recorded from single units in the inferior colliculus (IC) of unanesthetized rabbits in response to noise stimuli containing a brief segment with linearly time-varying interaural time difference ("ITD sweep") temporally embedded in interaurally uncorrelated noise. We also tested the ability of human listeners to either detect the ITD sweeps or identify the motion direction. Using a point-process model to separate the contributions of stimulus dependence and spiking history to single-neuron responses, we found that the neurons respond primarily by following the instantaneous ITD rather than exhibiting true direction selectivity. Furthermore, using an optimal classifier to decode the single-neuron responses, we found that neural threshold durations of ITD sweeps for both direction identification and detection overlapped with human threshold durations even though the average response of the neurons could track the instantaneous ITD beyond psychophysical limits. Our results suggest that the IC does not explicitly encode motion direction, but internal neural noise may limit the speed at which we can identify the direction of motion.NEW & NOTEWORTHY Recognizing motion and identifying an object's trajectory are important for parsing a complex auditory scene, but how we do so is unclear. We show that neurons in the auditory midbrain do not exhibit direction selectivity as found in the visual system but instead follow the trajectory of the motion in their temporal firing patterns. Our results suggest that the inherent variability in neural firings may limit our ability to identify motion direction at short durations.
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Affiliation(s)
- Nathaniel J Zuk
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts
| | - Bertrand Delgutte
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts.,Department of Otolaryngology, Harvard Medical School, Boston, Massachusetts
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Joris PX. Neural binaural sensitivity at high sound speeds: Single cell responses in cat midbrain to fast-changing interaural time differences of broadband sounds. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 145:EL45. [PMID: 30710960 PMCID: PMC7112706 DOI: 10.1121/1.5087524] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Revised: 12/13/2018] [Accepted: 12/18/2018] [Indexed: 06/09/2023]
Abstract
Relative motion between the body and the outside world is a rich source of information. Neural selectivity to motion is well-established in several sensory systems, but is controversial in hearing. This study examines neural sensitivity to changes in the instantaneous interaural time difference of sounds at the two ears. Midbrain neurons track such changes up to extremely high speeds, show only a coarse dependence of firing rate on speed, and lack directional selectivity. These results argue against the presence of selectivity to auditory motion at the level of the midbrain, but reveal an acuity which enables coding of fast-fluctuating binaural cues in realistic sound environments.
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Affiliation(s)
- Philip X Joris
- Laboratory of Auditory Neurophysiology, KU Leuven, Herestraat 49, B-3000 Leuven, Belgium
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Su Y, Delgutte B. Pitch of Harmonic Complex Tones: Rate Coding of Envelope Repetition Rate in the Auditory Midbrain. ACTA ACUST UNITED AC 2018; 104:860-864. [PMID: 30613198 PMCID: PMC6320231 DOI: 10.3813/aaa.919239] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Envelope repetition rate (ERR) is an important cue for the pitch of harmonic complex tones (HCT), especially when the tone consists entirely of unresolved harmonics. Neural synchronization to the stimulus envelope provides a prominent cue for ERR in the auditory periphery, but this temporal code becomes degraded and gives way to rate codes in higher centers. The inferior colliculus (IC) likely plays a key role in this temporal-to-rate code transformation. Here we recorded single IC neuron responses to HCT at varying fundamental frequencies (F 0). ERR was manipulated by applying different inter-harmonic phase relationships. We identified a subset of neurons that showed a 'non-tonotopic' rate tuning to ERR between 160 and 1500 Hz. A comparison of neural responses to HCT and sinusoidally amplitude modulated (SAM) noise suggests that this tuning is dependent on the shape of stimulus envelope. A phenomenological model is able to reproduce the non-tonotopic tuning to ERR, and suggests it arises in the IC via synaptic inhibition.
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Affiliation(s)
- Yaqing Su
- Eaton-Peabody Labs, Massachusetts Eye & Ear, Boston, MA, USA
- Dept. of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Bertrand Delgutte
- Eaton-Peabody Labs, Massachusetts Eye & Ear, Boston, MA, USA
- Dept. of Otolaryngology, Harvard Medical School, Boston, MA, USA
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