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Pan H, Zhang S, Pan D, Ye Z, Yu H, Ding J, Wang Q, Sun Q, Hua T. Characterization of Feedback Neurons in the High-Level Visual Cortical Areas That Project Directly to the Primary Visual Cortex in the Cat. Front Neuroanat 2021; 14:616465. [PMID: 33488364 PMCID: PMC7820340 DOI: 10.3389/fnana.2020.616465] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 12/04/2020] [Indexed: 12/17/2022] Open
Abstract
Previous studies indicate that top-down influence plays a critical role in visual information processing and perceptual detection. However, the substrate that carries top-down influence remains poorly understood. Using a combined technique of retrograde neuronal tracing and immunofluorescent double labeling, we characterized the distribution and cell type of feedback neurons in cat's high-level visual cortical areas that send direct connections to the primary visual cortex (V1: area 17). Our results showed: (1) the high-level visual cortex of area 21a at the ventral stream and PMLS area at the dorsal stream have a similar proportion of feedback neurons back projecting to the V1 area, (2) the distribution of feedback neurons in the higher-order visual area 21a and PMLS was significantly denser than in the intermediate visual cortex of area 19 and 18, (3) feedback neurons in all observed high-level visual cortex were found in layer II-III, IV, V, and VI, with a higher proportion in layer II-III, V, and VI than in layer IV, and (4) most feedback neurons were CaMKII-positive excitatory neurons, and few of them were identified as inhibitory GABAergic neurons. These results may argue against the segregation of ventral and dorsal streams during visual information processing, and support "reverse hierarchy theory" or interactive model proposing that recurrent connections between V1 and higher-order visual areas constitute the functional circuits that mediate visual perception. Also, the corticocortical feedback neurons from high-level visual cortical areas to the V1 area are mostly excitatory in nature.
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Affiliation(s)
- Huijun Pan
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Shen Zhang
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Deng Pan
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Zheng Ye
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Hao Yu
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Jian Ding
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Qin Wang
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Qingyan Sun
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Tianmiao Hua
- College of Life Sciences, Anhui Normal University, Wuhu, China
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Abstract
Neurons in visual areas of the brain are generally characterized by the increase in firing rate that occurs when a stimulus is flashed on in the receptive field (RF). However, neurons also increase their firing rate when a stimulus is turned off. These "termination responses" or "after-discharges" that occur with flashed stimuli have been observed in area V1 and they may be important for vision as stimulus terminations have been shown to influence visual perception. The goal of the present study was to determine the strength of termination responses in the more natural situation in which eye movements move a stimulus out of an RF. We find that termination responses do occur in macaque V1 when termination results from a saccadic eye movement, but they are smaller in amplitude compared to flashed-off stimuli. Furthermore, there are termination responses even in the absence of visual stimulation. These findings demonstrate that termination responses are a component of naturalistic vision. They appear to be based on both visual and nonvisual signals in visual cortex. We speculate that the weakening of termination responses might be a neural correlate of saccadic suppression, the loss of perceptual sensitivity around the time of saccades.
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Hietanen MA, Cloherty SL, Ibbotson MR. Contrast and response gain control depend on cortical map architecture. Eur J Neurosci 2015; 42:2963-73. [PMID: 26432621 DOI: 10.1111/ejn.13091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 09/23/2015] [Accepted: 09/28/2015] [Indexed: 11/29/2022]
Abstract
Visual cortical neurons are sensitive to visual stimulus contrast and most cells adapt their sensitivity to the prevailing visual environment. Specifically, they match the steepest region of their contrast response function to the prevailing contrast (contrast gain control), and reduce spike rates to limit saturation (response gain control). Most neurons are also tuned for stimulus orientation, and neurons with similar orientation preference are clustered together into iso-orientation zones arranged around pinwheels, i.e. points where all orientations are represented. Here we investigated the relationship between the contrast adaptation properties of neurons and their location relative to pinwheels in the orientation preference map. We measured orientation preference maps in cat cortex using optical intrinsic signal imaging. We then characterized the contrast adaptation properties of single neurons located close to pinwheels, in iso-orientation zones, and at regions in between. We found little evidence of differential contrast sensitivity of neurons adapted to zero contrast. However, after adaptation to their preferred orientation at high contrast, changes in both contrast and response gain were greater for neurons near pinwheels compared with other map regions. Therefore, in the adapted state, which is probably typical during natural viewing, there is a spatial map of contrast sensitivity that is associated with the orientation preference map. This differential adaptation revealed a new dimension of cortical functional organization, linking the contrast adaptation of cells with the orientation preference of their nearest neighbours.
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Affiliation(s)
- Markus A Hietanen
- National Vision Research Institute, Australian College of Optometry, Cnr Cardigan and Keppel Street, Carlton, Vic., 3053, Australia.,ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Vic., Australia
| | - Shaun L Cloherty
- National Vision Research Institute, Australian College of Optometry, Cnr Cardigan and Keppel Street, Carlton, Vic., 3053, Australia.,ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Vic., Australia.,Department of Electrical and Electronic Engineering, University of Melbourne, Parkville, Vic., Australia
| | - Michael R Ibbotson
- National Vision Research Institute, Australian College of Optometry, Cnr Cardigan and Keppel Street, Carlton, Vic., 3053, Australia.,ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Vic., Australia
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Meffin H, Hietanen MA, Cloherty SL, Ibbotson MR. Spatial phase sensitivity of complex cells in primary visual cortex depends on stimulus contrast. J Neurophysiol 2015; 114:3326-38. [PMID: 26378205 DOI: 10.1152/jn.00431.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 09/10/2015] [Indexed: 11/22/2022] Open
Abstract
Neurons in primary visual cortex are classified as simple, which are phase sensitive, or complex, which are significantly less phase sensitive. Previously, we have used drifting gratings to show that the phase sensitivity of complex cells increases at low contrast and after contrast adaptation while that of simple cells remains the same at all contrasts (Cloherty SL, Ibbotson MR. J Neurophysiol 113: 434-444, 2015; Crowder NA, van Kleef J, Dreher B, Ibbotson MR. J Neurophysiol 98: 1155-1166, 2007; van Kleef JP, Cloherty SL, Ibbotson MR. J Physiol 588: 3457-3470, 2010). However, drifting gratings confound the influence of spatial and temporal summation, so here we have stimulated complex cells with gratings that are spatially stationary but continuously reverse the polarity of the contrast over time (contrast-reversing gratings). By varying the spatial phase and contrast of the gratings we aimed to establish whether the contrast-dependent phase sensitivity of complex cells results from changes in spatial or temporal processing or both. We found that most of the increase in phase sensitivity at low contrasts could be attributed to changes in the spatial phase sensitivities of complex cells. However, at low contrasts the complex cells did not develop the spatiotemporal response characteristics of simple cells, in which paired response peaks occur 180° out of phase in time and space. Complex cells that increased their spatial phase sensitivity at low contrasts were significantly overrepresented in the supragranular layers of cortex. We conclude that complex cells in supragranular layers of cat cortex have dynamic spatial summation properties and that the mechanisms underlying complex cell receptive fields differ between cortical layers.
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Affiliation(s)
- H Meffin
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia; ARC Centre of Excellence for Integrative Brain Function, Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia; and
| | - M A Hietanen
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia; ARC Centre of Excellence for Integrative Brain Function, Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia; and
| | - S L Cloherty
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia; ARC Centre of Excellence for Integrative Brain Function, Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia; and Department of Electrical and Electronic Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - M R Ibbotson
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia; ARC Centre of Excellence for Integrative Brain Function, Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia; and
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Hietanen MA. The relative contributions of global and local acceleration components on speed perception and discriminability following adaptation. Vision Res 2015; 115:135-41. [PMID: 26278165 DOI: 10.1016/j.visres.2015.06.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/12/2015] [Accepted: 06/23/2015] [Indexed: 11/13/2022]
Abstract
The perception of speed is dependent on the history of previously presented speeds. Adaptation to a given speed regularly results in a reduction of perceived speed and an increase in speed discriminability and in certain circumstances can result in an increase in perceived speed. In order to determine the relative contributions of the local and global speed components on perceived speed, this experiment used expanding dot flow fields with accelerating (global), decelerating (global) and mixed accelerating/decelerating (local) speed patterns. Profound decreases in perceived speed are found when viewing low test speeds after adaptation to high speeds. Small increases in the perceived speed of high test speeds occur following adaptation to low speeds. There were small but significant differences in perceived stimulus speed after adaptation due to different acceleration profiles. No evidence for global modulation of speed discriminability following adaptation was found.
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Affiliation(s)
- Markus A Hietanen
- National Vision Research Institute, Australian College of Optometry, Cnr Cardigan and Keppel Street, Carlton, VIC 3053, Australia; ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, VIC 3010, Australia.
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Wang Z, Li G, Yuan N, Xu G, Wang X, Zhou Y. Acute alcohol exposure impairs neural representation of visual motion speed in the visual cortex area posteromedial lateral suprasylvian cortex of cats. Alcohol Clin Exp Res 2015; 39:640-9. [PMID: 25833025 DOI: 10.1111/acer.12684] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 01/16/2015] [Indexed: 11/27/2022]
Abstract
BACKGROUND Psychophysical and behavioral studies have demonstrated that perception of motion can be impaired by acute alcohol exposure. The neural activities of posteromedial lateral suprasylvian cortex (PMLS) of cats are directly linked to the perception of visual motion speed. To date, there have been no studies on the effects of acute alcohol exposure in vivo upon the representation of speed in PMLS neurons. METHODS Alcohol was administered intravenously as a 20% (v/v) saline solution via a syringe at a dose levels of 0.5, 1, or 2 g/kg to generate a series of blood alcohol concentrations. Using extracellular single-unit recording technique, we recorded the speed-tuning properties of PMLS neurons that responded to random-dot patterns before and after alcohol administration, and simultaneously monitored the concentration of ethanol by detecting the breath alcohol concentration using a breath analyzer. RESULTS After acute alcohol treatment, PMLS cells preferred lower speeds. A broadened speed-tuning bandwidth of PMLS cells was also observed after acute alcohol administration. Additionally, response modulation and discriminative capacity for speed of visual motion in the PMLS cells were significantly impaired after acute alcohol exposure. Concurrently, PMLS cells after acute alcohol exposure showed decreased spontaneous activity, peak responses, and signal-to-noise ratios. CONCLUSIONS There is a significant functional degradation in the neural representation of visual motion speed in PMLS of cats after acute alcohol exposure. These neural changes may contribute to the alcohol-related deficits in visual motion perception observed in behavioral studies.
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Affiliation(s)
- Zhengchun Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences , University of Science and Technology of China, Hefei, Anhui, China
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Tanaka T, Nishida S, Aso T, Ogawa T. Visual response of neurons in the lateral intraparietal area and saccadic reaction time during a visual detection task. Eur J Neurosci 2012; 37:942-56. [PMID: 23279068 DOI: 10.1111/ejn.12100] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2012] [Revised: 11/06/2012] [Accepted: 11/19/2012] [Indexed: 11/28/2022]
Abstract
During visual detection with saccades, a target with higher luminance is detected with reduced reaction times. In such visual detection behaviors, luminance-related sensory signals should be converted into movement-related signals for saccade initiation. At the site where the visuomotor transformation takes place, there is the possibility that visual activity not only encodes the target luminance but also affects the generation of an upcoming saccade. To assess this possibility, we recorded single-cell activity from visually responsive neurons in the lateral intraparietal area (LIP) when monkeys made a saccade to an isolated target over five luminance levels. We found that as stimulus luminance increased, visual response strength increased, and response onset latency decreased. These luminance-related changes in activity were significantly correlated with changes in reaction time. In particular, changes in response onset latency accounted for a substantial part of the observed changes in reaction time, suggesting that luminance-related changes in response onset latency may propagate to the saccade generation process. However, the length of time from response onset to saccade onset was not constant but increased as luminance was reduced, suggesting the existence of other luminance-dependent processing in downstream and/or parallel pathways before saccade generation. Additionally, we failed to find strong covariance between response strength or latency and reaction time when the effect of luminance changes was removed. Thus, the present results reveal how visually responsive LIP neurons contribute to saccade generation in visual detection.
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Affiliation(s)
- Tomohiro Tanaka
- Department of Integrative Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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Traschütz A, Zinke W, Wegener D. Speed change detection in foveal and peripheral vision. Vision Res 2012; 72:1-13. [DOI: 10.1016/j.visres.2012.08.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 08/06/2012] [Accepted: 08/31/2012] [Indexed: 10/27/2022]
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Barnes T, Mingolla E. Representation of motion onset and offset in an augmented Barlow-Levick model of motion detection. J Comput Neurosci 2012; 33:421-34. [PMID: 22528025 PMCID: PMC3484280 DOI: 10.1007/s10827-012-0393-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 03/26/2012] [Accepted: 03/28/2012] [Indexed: 12/20/2022]
Abstract
Kinetic occlusion produces discontinuities in the optic flow field, whose perception requires the detection of an unexpected onset or offset of otherwise predictably moving or stationary contrast patches. Many cells in primate visual cortex are directionally selective for moving contrasts, and recent reports suggest that this selectivity arises through the inhibition of contrast signals moving in the cells' null direction, as in the rabbit retina. This nulling inhibition circuit (Barlow-Levick) is here extended to also detect motion onsets and offsets. The selectivity of extended circuit units, measured as a peak evidence accumulation response to motion onset/offset compared to the peak response to constant motion, is analyzed as a function of stimulus speed. Model onset cells are quiet during constant motion, but model offset cells activate during constant motion at slow speeds. Consequently, model offset cell speed tuning is biased towards higher speeds than onset cell tuning, similarly to the speed tuning of cells in the middle temporal area when exposed to speed ramps. Given a population of neurons with different preferred speeds, this asymmetry addresses a behavioral paradox-why human subjects in a simple reaction time task respond more slowly to motion offsets than onsets for low speeds, even though monkey neuron firing rates react more quickly to the offset of a preferred stimulus than to its onset.
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Affiliation(s)
- Timothy Barnes
- Program in Cognitive and Neural Systems, Boston University, Boston, MA 02215, USA.
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Nordström K, Moyer de Miguel I, O'Carroll DC. Rapid contrast gain reduction following motion adaptation. ACTA ACUST UNITED AC 2012; 214:4000-9. [PMID: 22071192 DOI: 10.1242/jeb.057539] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neural and sensory systems adapt to prolonged stimulation to allow signaling across broader input ranges than otherwise possible with the limited bandwidth of single neurons and receptors. In the visual system, adaptation takes place at every stage of processing, from the photoreceptors that adapt to prevailing luminance conditions, to higher-order motion-sensitive neurons that adapt to prolonged exposure to motion. Recent experiments using dynamic, fluctuating visual stimuli indicate that adaptation operates on a time scale similar to that of the response itself. Further work from our own laboratory has highlighted the role for rapid motion adaptation in reliable encoding of natural image motion. Physiologically, motion adaptation can be broken down into four separate components. It is not clear from the previous studies which of these motion adaptation components are involved in the fast and dynamic response changes. To investigate the adapted response in more detail, we therefore analyzed the effect of motion adaptation using a test-adapt-test protocol with adapting durations ranging from 20 ms to 20 s. Our results underscore the very rapid rate of motion adaptation, suggesting that under free flight, visual motion-sensitive neurons continuously adapt to the changing scenery. This might help explain recent observations of strong invariance in the response to natural scenes with highly variable contrast and image structure.
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Affiliation(s)
- Karin Nordström
- Department of Neuroscience, Uppsala University, Uppsala, Sweden.
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Abstract
It is generally accepted that in mammals visual information is sent to the brain along functionally specialized parallel pathways, but whether the mouse visual system uses similar processing strategies is not known. It is important to resolve this issue because the mouse brain provides a tractable system for developing a cellular and molecular understanding of disorders affecting spatiotemporal visual processing. We have used single-unit recordings in mouse primary visual cortex to study whether individual neurons are more sensitive to one set of sensory cues than another. Our quantitative analyses show that neurons with short response latencies have low spatial acuity and high sensitivity to contrast, temporal frequency, and speed, whereas neurons with long latencies have high spatial acuity, low sensitivities to contrast, temporal frequency, and speed. These correlations suggest that neurons in mouse V1 receive inputs from a weighted combination of parallel afferent pathways with distinct spatiotemporal sensitivities.
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Pinto L, Baron J. Spatiotemporal frequency tuning dynamics of neurons in the owl visual wulst. J Neurophysiol 2010; 103:3424-36. [PMID: 20393061 DOI: 10.1152/jn.01151.2009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The transformation of spatial (SF) and temporal frequency (TF) tuning functions from broad-band/low-pass to narrow band-pass profiles is one of the key emergent properties of neurons in the mammalian primary visual cortex (V1). The mechanisms underlying such transformation are still a matter of ongoing debate. With the aim of providing comparative insights into the issue, we analyzed various aspects of the spatiotemporal tuning dynamics of neurons in the visual wulst of four awake owls. The wulst is the avian telencephalic target of the retinothalamofugal pathway and, in owls, bears striking functional analogy with V1. Most neurons in our sample exhibited fast and large-magnitude adaptation to the visual stimuli with response latencies very similar to those reported for V1. Moreover, latency increased as a function of stimulus SF but not TF, which suggests that parvo- and magno-like geniculate inputs could be converging onto single wulst neurons. No net shifts in preferred SF or TF were observed along the initial second of stimulation, but bandwidth decreased roughly during the first 200 ms after response latency for both stimulus dimensions. For SF, this occurred exclusively as a consequence of low-frequency suppression, whereas suppression was observed both at the low- and high-frequency limbs of TF tuning curves. Overall these results indicate that SF and TF tuning curves in the wulst are shaped by both feedforward and intratelencephalic suppressive mechanisms, similarly to what seems to be the case in the mammalian striate cortex.
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Affiliation(s)
- Lucas Pinto
- Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil
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Crowder NA, Price NSC, Mustari MJ, Ibbotson MR. Direction and contrast tuning of macaque MSTd neurons during saccades. J Neurophysiol 2009; 101:3100-7. [PMID: 19357345 DOI: 10.1152/jn.91254.2008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Saccades are rapid eye movements that change the direction of gaze, although the full-field image motion associated with these movements is rarely perceived. The attenuation of visual perception during saccades is referred to as saccadic suppression. The mechanisms that produce saccadic suppression are not well understood. We recorded from neurons in the dorsal medial superior temporal area (MSTd) of alert macaque monkeys and compared the neural responses produced by the retinal slip associated with saccades (active motion) to responses evoked by identical motion presented during fixation (passive motion). We provide evidence for a neural correlate of saccadic suppression and expand on two contentious results from previous studies. First, we confirm the finding that some neurons in MSTd reverse their preferred direction during saccades. We quantify this effect by calculating changes in direction tuning index for a large cell population. Second, it has been noted that neural activity associated with saccades can arrive in the parietal cortex <or=30 ms earlier than activity produced by similar visual stimulation during fixation. This led to the question of whether the saccade-related responses were visual in origin or were motor signals arising from saccade-planning areas of the brain. By comparing the responses to saccades made over textured backgrounds of different contrasts, we provide strong evidence that saccade-related responses were visual in origin. Refinements of the possible models of saccadic suppression are discussed.
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Affiliation(s)
- Nathan A Crowder
- Visual Sciences Group and Australian Research Council Centre of Excellence in Vision Science, Australian National University, Canberra, Australian Capital Territory, Australia 2601
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Crowder NA, van Kleef J, Dreher B, Ibbotson MR. Complex Cells Increase Their Phase Sensitivity at Low Contrasts and Following Adaptation. J Neurophysiol 2007; 98:1155-66. [PMID: 17537901 DOI: 10.1152/jn.00433.2007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
One of the best-known dichotomies in neuroscience is the division of neurons in the mammalian primary visual cortex into simple and complex cells. Simple cells have receptive fields with separate on and off subregions and give phase-sensitive responses to moving gratings, whereas complex cells have uniform receptive fields and are phase invariant. The phase sensitivity of a cell is calculated as the ratio of the first Fourier coefficient ( F1) to the mean time-average ( F0) of the response to moving sinusoidal gratings at 100% contrast. Cells are then classified as simple ( F1/ F0>1) or complex ( F1/ F0<1). We manipulated cell responses by changing the stimulus contrast or through adaptation. The F1/ F0ratios of cells defined as complex at 100% contrast increased at low contrasts and following adaptation. Conversely, the F1/ F0ratios remained constant for cells defined as simple at 100% contrast. The latter cell type was primarily located in thalamorecipient layers 4 and 6. Many cells initially classified as complex exhibit F1/ F0>1 at low contrasts and after adaptation (particularly in layer 4). The results are consistent with the spike-threshold hypothesis, which suggests that the division of cells into two types arises from the nonlinear interaction of spike threshold with membrane potential responses.
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Affiliation(s)
- N A Crowder
- Visual Sciences, Research School of Biological Sciences, Australian National University, Canberra, ACT, Australia 2601
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15
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Hietanen MA, Crowder NA, Price NSC, Ibbotson MR. Influence of adapting speed on speed and contrast coding in the primary visual cortex of the cat. J Physiol 2007; 584:451-62. [PMID: 17702823 PMCID: PMC2277174 DOI: 10.1113/jphysiol.2007.131631] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Adaptation is a ubiquitous property of the visual system. Adaptation often improves the ability to discriminate between stimuli and increases the operating range of the system, but is also associated with a reduced ability to veridically code stimulus attributes. Adaptation to luminance levels, contrast, orientation, direction and spatial frequency has been studied extensively, but knowledge about adaptation to image speed is less well understood. Here we examined how the speed tuning of neurons in cat primary visual cortex was altered after adaptation to speeds that were slow, optimal, or fast relative to each neuron's speed response function. We found that the preferred speed (defined as the speed eliciting the peak firing rate) of the neurons following adaptation was dependent on the speed at which they were adapted. At the population level cells showed decreases in preferred speed following adaptation to speeds at or above the non-adapted speed, but the preferred speed did not change following adaptation to speeds lower than the non-adapted peak. Almost all cells showed response gain control (reductions in absolute firing capacity) following speed adaptation. We also investigated the speed dependence of contrast adaptation and found that most cells showed contrast gain control (rightward shifts of their contrast response functions) and response gain control following adaptation at any speed. We conclude that contrast adaptation may produce the response gain control associated with speed adaptation, but shifts in preferred speed require an additional level of processing beyond contrast adaptation. A simple model is presented that is able to capture most of the findings.
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Affiliation(s)
- M A Hietanen
- Visual Sciences, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia
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Hietanen MA, Crowder NA, Ibbotson MR. Contrast gain control is drift-rate dependent: an informational analysis. J Neurophysiol 2006; 97:1078-87. [PMID: 17122311 DOI: 10.1152/jn.00991.2006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neurons in the visual cortex code relative changes in illumination (contrast) and adapt their sensitivities to the visual scene by centering the steepest regions of their sigmoidal contrast response functions (CRFs: spike rate as a function of contrast) on the prevailing contrast. The influence of this contrast gain control has not been reported at nonoptimal drift rates. We calculated the Fisher information contained in the CRFs of halothane-anesthetized cats. Fisher information gives a measure of the accuracy of contrast representations based on the ratio of the square of the steepness of the CRF and the spike-rate dependency of the spiking variance. Variance increases with spike rate, so Fisher information is maximal where the CRF is steep and spike rates are low. Here, we show that the contrast at which the maximal Fisher information (C(MFI)) occurs for each adapting drift rate is at a fixed level above the adapting contrast. For adapting contrasts of 0 to 0.32 the relationship between C(MFI) and adapting contrast is well described by a straight line with a slope close to 1. The intercept of this line on the C(MFI)-axis is drift-rate dependent, although the slope is not. At high drift rates relative to each cell's peak the C(MFI) offset is higher than that for low drift rates. The results show that the contrast coding strategy in visual cortex maximizes accuracy for contrasts above the prevailing contrast in the environment for all drift rates. We argue that tuning the system for accuracy at contrasts above the prevailing value is optimal for viewing natural scenes.
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Affiliation(s)
- M A Hietanen
- Visual Sciences, Research School of Biological Sciences, Australian National University, Canberra, ACT, Australia 2601
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