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Tian F, Zhang Y, Schriver KE, Hu JM, Roe AW. A novel interface for cortical columnar neuromodulation with multipoint infrared neural stimulation. Nat Commun 2024; 15:6528. [PMID: 39095351 PMCID: PMC11297274 DOI: 10.1038/s41467-024-50375-0] [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: 06/10/2023] [Accepted: 07/09/2024] [Indexed: 08/04/2024] Open
Abstract
Cutting edge advances in electrical visual cortical prosthetics have evoked perception of shapes, motion, and letters in the blind. Here, we present an alternative optical approach using pulsed infrared neural stimulation. To interface with dense arrays of cortical columns with submillimeter spatial precision, both linear array and 100-fiber bundle array optical fiber interfaces were devised. We deliver infrared stimulation through these arrays in anesthetized cat visual cortex and monitor effects by optical imaging in contralateral visual cortex. Infrared neural stimulation modulation of response to ongoing visual oriented gratings produce enhanced responses in orientation-matched domains and suppressed responses in non-matched domains, consistent with a known higher order integration mediated by callosal inputs. Controls include dynamically applied speeds, directions and patterns of multipoint stimulation. This provides groundwork for a distinct type of prosthetic targeted to maps of visual cortical columns.
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Affiliation(s)
- Feiyan Tian
- Department of Neurosurgery of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University, Hangzhou, 310029, China
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, 310027, China
| | - Ying Zhang
- Department of Neurosurgery of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University, Hangzhou, 310029, China
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, 310027, China
| | - Kenneth E Schriver
- Department of Neurosurgery of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University, Hangzhou, 310029, China
- MOE Frontier Science Center for Brain Science and Brain-machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, 310012, China
| | - Jia Ming Hu
- Department of Neurosurgery of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University, Hangzhou, 310029, China.
- MOE Frontier Science Center for Brain Science and Brain-machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, 310012, China.
| | - Anna Wang Roe
- Department of Neurosurgery of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University, Hangzhou, 310029, China.
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, 310027, China.
- MOE Frontier Science Center for Brain Science and Brain-machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, 310012, China.
- National Key Laboratory of Brain and Computer Intelligence, Zhejiang University, Hangzhou, 310058, China.
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2
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Saeedi A, Wang K, Nikpourian G, Bartels A, Logothetis NK, Totah NK, Watanabe M. Brightness illusions drive a neuronal response in the primary visual cortex under top-down modulation. Nat Commun 2024; 15:3141. [PMID: 38653975 DOI: 10.1038/s41467-024-46885-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Accepted: 03/13/2024] [Indexed: 04/25/2024] Open
Abstract
Brightness illusions are a powerful tool in studying vision, yet their neural correlates are poorly understood. Based on a human paradigm, we presented illusory drifting gratings to mice. Primary visual cortex (V1) neurons responded to illusory gratings, matching their direction selectivity for real gratings, and they tracked the spatial phase offset between illusory and real gratings. Illusion responses were delayed compared to real gratings, in line with the theory that processing illusions requires feedback from higher visual areas (HVAs). We provide support for this theory by showing a reduced V1 response to illusions, but not real gratings, following HVAs optogenetic inhibition. Finally, we used the pupil response (PR) as an indirect perceptual report and showed that the mouse PR matches the human PR to perceived luminance changes. Our findings resolve debates over whether V1 neurons are involved in processing illusions and highlight the involvement of feedback from HVAs.
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Affiliation(s)
- Alireza Saeedi
- Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076, Tübingen, Germany
- Research Group Neurobiology of Magnetoreception, Max Planck Institute for Neurobiology of Behavior - caesar, 53175, Bonn, Germany
| | - Kun Wang
- Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076, Tübingen, Germany
- Department of Physiology of Cognitive Processes, International Center for Primate Brain Research, Songjiang District, Shanghai, 201602, China
| | - Ghazaleh Nikpourian
- Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076, Tübingen, Germany
| | - Andreas Bartels
- Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076, Tübingen, Germany
- Department of Psychology, Vision and Cognition Lab, Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany
- Bernstein Center for Computational Neuroscience, Tübingen, Germany
| | - Nikos K Logothetis
- Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076, Tübingen, Germany
- Department of Physiology of Cognitive Processes, International Center for Primate Brain Research, Songjiang District, Shanghai, 201602, China
- Centre for Imaging Sciences, University of Manchester, Manchester, M139PT, UK
| | - Nelson K Totah
- Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076, Tübingen, Germany.
- Helsinki Institute of Life Science (HILIFE), University of Helsinki, 00014, Helsinki, Finland.
- Faculty of Pharmacy, University of Helsinki, 00014, Helsinki, Finland.
- Neuroscience Center, University of Helsinki, 00014, Helsinki, Finland.
| | - Masataka Watanabe
- Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076, Tübingen, Germany.
- Department of Systems Innovation, School of Engineering, The University of Tokyo, Tokyo, Japan.
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3
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Su X, Zhou M, Di L, Chen J, Zhai Z, Liang J, Li L, Li H, Chai X. The Visual Cortical Responses to Sinusoidal Transcorneal Electrical Stimulation. Brain Res 2022; 1785:147875. [PMID: 35271821 DOI: 10.1016/j.brainres.2022.147875] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 03/04/2022] [Accepted: 03/05/2022] [Indexed: 11/25/2022]
Abstract
Retinal stimulation has become a widely utilized approach to restore visual function for individuals with retinal degenerative diseases. Although the rectangular electrical pulse is the primary stimulus waveform used in retinal neuromodulation, it remains unclear whether alternate waveforms may be more effective. Here, we used the optical intrinsic signal imaging system to assess the responses of cats' visual cortex to sinusoidal electrical stimulation through contact lens electrode, analyzing the response to various stimulus parameters (frequency, intensity, pulse width). A comparison between sinusoidal and rectangular stimulus waveform was also investigated. The results indicated that the optimal stimulation frequency for sinusoidal electrical stimulation was approximately 20 Hz, supporting the hypothesis that low-frequency electrostimulation induces more responsiveness in retinal neurons than high-frequency electrostimulation in case of sinusoidal stimulation. We also demonstrated that for low-frequency retinal neuromodulation, sinusoidal pulses are more effective than rectangular ones. In addition, we found that compared to current intensity, the effect of the sinusoidal pulse width on cortical responses was more prominent. These results suggested that sinusoidal electrical stimulation may provide a promising strategy for improved retinal neuromodulation in clinical settings.
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Affiliation(s)
- Xiaofan Su
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Meixuan Zhou
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Liqing Di
- Department of Orthopedics, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China
| | - Jianpin Chen
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Zhenzhen Zhai
- The Network & Information Center, Shanghai Jiao Tong University, Shanghai, China
| | - Junling Liang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Heng Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Xinyu Chai
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
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4
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Lerer A, Supèr H, Keil MS. Dynamic decorrelation as a unifying principle for explaining a broad range of brightness phenomena. PLoS Comput Biol 2021; 17:e1007907. [PMID: 33901165 PMCID: PMC8102013 DOI: 10.1371/journal.pcbi.1007907] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Revised: 05/06/2021] [Accepted: 04/06/2021] [Indexed: 11/29/2022] Open
Abstract
The visual system is highly sensitive to spatial context for encoding luminance patterns. Context sensitivity inspired the proposal of many neural mechanisms for explaining the perception of luminance (brightness). Here we propose a novel computational model for estimating the brightness of many visual illusions. We hypothesize that many aspects of brightness can be explained by a dynamic filtering process that reduces the redundancy in edge representations on the one hand, while non-redundant activity is enhanced on the other. The dynamic filter is learned for each input image and implements context sensitivity. Dynamic filtering is applied to the responses of (model) complex cells in order to build a gain control map. The gain control map then acts on simple cell responses before they are used to create a brightness map via activity propagation. Our approach is successful in predicting many challenging visual illusions, including contrast effects, assimilation, and reverse contrast with the same set of model parameters.
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Affiliation(s)
- Alejandro Lerer
- Departament de Cognició, Desenvolupament i Psicologia de l’Educació, Faculty of Psychology, University of Barcelona, Barcelona, Spain
| | - Hans Supèr
- Departament de Cognició, Desenvolupament i Psicologia de l’Educació, Faculty of Psychology, University of Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain
- Institut de Recerca Pediàtrica Hospital Sant Joan de Déu, Barcelona, Spain
- Catalan Institute for Advanced Studies (ICREA), Barcelona, Spain
| | - Matthias S. Keil
- Departament de Cognició, Desenvolupament i Psicologia de l’Educació, Faculty of Psychology, University of Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain
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5
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Sun P, Li H, Lu Z, Su X, Ma Z, Chen J, Li L, Zhou C, Chen Y, Chai X. Comparison of cortical responses to the activation of retina by visual stimulation and transcorneal electrical stimulation. Brain Stimul 2018. [DOI: 10.1016/j.brs.2018.02.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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6
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Meng J, Li Z, Li H, Zhu J, Yu H. The Common and Distinct Orientation Adaptation Effect at Pinwheel Centers in Areas 21a and 17 of Cats. Neuroscience 2018; 379:77-92. [DOI: 10.1016/j.neuroscience.2018.03.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 03/02/2018] [Accepted: 03/05/2018] [Indexed: 11/16/2022]
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7
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The feature-specific propagation of orientation and direction adaptation from areas 17 to 21a in cats. Sci Rep 2017; 7:390. [PMID: 28341863 PMCID: PMC5428465 DOI: 10.1038/s41598-017-00419-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 02/21/2017] [Indexed: 11/30/2022] Open
Abstract
Adaptation plays a key role in visual information processing, and investigations on the adaptation across different visual regions will be helpful to understand how information is processed dynamically along the visual streams. Recent studies have found the enhanced adaptation effects in the early visual system (from LGN to V1) and the dorsal stream (from V1 to MT). However, it remains unclear how adaptation effect propagates along the form/orientation stream in the visual system. In this study, we compared the orientation and direction adaptation evoked by drifting gratings and stationary flashing gratings, as well as moving random dots, in areas 17 and 21a simultaneously of cats. Recorded by single-unit and intrinsic signal optical imaging, induced by both top-up and biased adaptation protocols, the orientation adaptation effect was greater in response decline and preferred orientation shifts in area 21a compared to area 17. However, for the direction adaptation, no difference was observed between these two areas. These results suggest the feature-specific propagation of the adaptation effect along the visual stream.
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8
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Smith GB, Whitney DE, Fitzpatrick D. Modular Representation of Luminance Polarity in the Superficial Layers of Primary Visual Cortex. Neuron 2016; 88:805-18. [PMID: 26590348 DOI: 10.1016/j.neuron.2015.10.019] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 09/23/2015] [Accepted: 10/06/2015] [Indexed: 10/22/2022]
Abstract
The spatial arrangement of luminance increments (ON) and decrements (OFF) falling on the retina provides a wealth of information used by central visual pathways to construct coherent representations of visual scenes. But how the polarity of luminance change is represented in the activity of cortical circuits remains unclear. Using wide-field epifluorescence and two-photon imaging we demonstrate a robust modular representation of luminance polarity (ON or OFF) in the superficial layers of ferret primary visual cortex. Polarity-specific domains are found with both uniform changes in luminance and single light/dark edges, and include neurons selective for orientation and direction of motion. The integration of orientation and polarity preference is evident in the selectivity and discrimination capabilities of most layer 2/3 neurons. We conclude that polarity selectivity is an integral feature of layer 2/3 neurons, ensuring that the distinction between light and dark stimuli is available for further processing in downstream extrastriate areas.
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Affiliation(s)
- Gordon B Smith
- Department of Functional Architecture and Development of Cerebral Cortex, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - David E Whitney
- Department of Functional Architecture and Development of Cerebral Cortex, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - David Fitzpatrick
- Department of Functional Architecture and Development of Cerebral Cortex, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA.
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9
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Abstract
UNLABELLED The neuronal mechanism underlying the representation of color surfaces in primary visual cortex (V1) is not well understood. We tested on color surfaces the previously proposed hypothesis that visual perception of uniform surfaces is mediated by an isomorphic, filled-in representation in V1. We used voltage-sensitive-dye imaging in fixating macaque monkeys to measure V1 population responses to spatially uniform chromatic (red, green, or blue) and achromatic (black or white) squares of different sizes (0.5°-8°) presented for 300 ms. Responses to both color and luminance squares early after stimulus onset were similarly edge-enhanced: for squares 1° and larger, regions corresponding to edges were activated much more than those corresponding to the center. At later times after stimulus onset, responses to achromatic squares' centers increased, partially "filling-in" the V1 representation of the center. The rising phase of the center response was slower for larger squares. Surprisingly, the responses to color squares behaved differently. For color squares of all sizes, responses remained edge-enhanced throughout the stimulus. There was no filling-in of the center. Our results imply that uniform filled-in representations of surfaces in V1 are not required for the perception of uniform surfaces and that chromatic and achromatic squares are represented differently in V1. SIGNIFICANCE STATEMENT We used voltage-sensitive dye imaging from V1 of behaving monkeys to test the hypothesis that visual perception of uniform surfaces is mediated by an isomorphic, filled-in representation. We found that the early population responses to chromatic and achromatic surfaces are edge enhanced, emphasizing the importance of edges in surface processing. Next, we show for color surfaces that responses remained edge-enhanced throughout the stimulus presentation whereas response to luminance surfaces showed a slow neuronal 'filling-in' of the center. Our results suggest that isomorphic representation is not a general code for uniform surfaces in V1.
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Yang X, Ding H, Lu J. Feedback from visual cortical area 7 to areas 17 and 18 in cats: How neural web is woven during feedback. Neuroscience 2015; 312:190-200. [PMID: 26592718 DOI: 10.1016/j.neuroscience.2015.11.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 10/10/2015] [Accepted: 11/09/2015] [Indexed: 11/26/2022]
Abstract
To investigate the feedback effect from area 7 to areas 17 and 18, intrinsic signal optical imaging combined with pharmacological, morphological methods and functional magnetic resonance imaging (fMRI) was employed. A spatial frequency-dependent decrease in response amplitude of orientation maps was observed in areas 17 and 18 when area 7 was inactivated by a local injection of GABA, or by a lesion induced by liquid nitrogen freezing. The pattern of orientation maps of areas 17 and 18 after the inactivation of area 7, if they were not totally blurred, paralleled the normal one. In morphological experiments, after one point at the shallow layers within the center of the cat's orientation column of area 17 was injected electrophoretically with HRP (horseradish peroxidase), three sequential patches in layers 1, 2 and 3 of area 7 were observed. Employing fMRI it was found that area 7 feedbacks mainly to areas 17 and 18 on ipsilateral hemisphere. Therefore, our conclusions are: (1) feedback from area 7 to areas 17 and 18 is spatial frequency modulated; (2) feedback from area 7 to areas 17 and 18 occurs mainly ipsilaterally; (3) histological feedback pattern from area 7 to area 17 is weblike.
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Affiliation(s)
- X Yang
- Life Science School, Fudan University, Shanghai 200433, China; Center of Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 55455, USA.
| | - H Ding
- Huaiyin Normal University, Huaian 223300, China
| | - J Lu
- The Advanced Institute of Translational Medicine and School of Software Engineering, Tongji University, Shanghai 200073, China.
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11
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Visual mismatch negativity is sensitive to illusory brightness changes. Brain Res 2014; 1561:48-59. [DOI: 10.1016/j.brainres.2014.03.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 02/25/2014] [Accepted: 03/10/2014] [Indexed: 11/21/2022]
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12
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Zheng L, Yao H. Stimulus-entrained oscillatory activity propagates as waves from area 18 to 17 in cat visual cortex. PLoS One 2012; 7:e41960. [PMID: 22848673 PMCID: PMC3405032 DOI: 10.1371/journal.pone.0041960] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Accepted: 06/27/2012] [Indexed: 11/21/2022] Open
Abstract
Previous studies in cat visual cortex reported that area 18 can actively drive neurons in area 17 through cortico-cortical projections. However, the dynamics of such cortico-cortical interaction remains unclear. Here we used multielectrode arrays to examine the spatiotemporal pattern of neuronal activity in cat visual cortex across the 17/18 border. We found that full-field contrast reversal gratings evoked oscillatory wave activity propagating from area 18 to 17. The wave direction was independent of the grating orientation, and could not be accounted for by the spatial distribution of receptive field latencies, suggesting that the waves are largely mediated by intrinsic connections in the cortex. Different from the evoked waves, spontaneous waves propagated along both directions across the 17/18 border. Together, our results suggest that visual stimulation may enhance the flow of information from area 18 to 17.
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Affiliation(s)
- Lian Zheng
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
- Graduate School of Chinese Academy of Sciences, Shanghai, China
| | - Haishan Yao
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
- * E-mail:
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Tani T, Ribot J, O'Hashi K, Tanaka S. Parallel development of orientation maps and spatial frequency selectivity in cat visual cortex. Eur J Neurosci 2012; 35:44-55. [PMID: 22211742 DOI: 10.1111/j.1460-9568.2011.07954.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In an early stage of the postnatal development of cats, orientation maps mature and spatial frequency selectivity is consolidated. To investigate the time course of orientation map maturation associated with the consolidation of spatial frequency selectivity, we performed optical imaging of intrinsic signals in areas 17 and 18 of cats under the stimulation of drifting square-wave gratings with different orientations and spatial frequencies. First, orientation maps for lower spatial frequencies emerged in the entire part of the lateral gyrus, which includes areas 17 and 18, and then these orientation maps in the posterior part of the lateral gyrus disappeared as orientation maps for higher spatial frequencies matured. Independent of age, an anteroposterior gradient of response strengths from lower to higher spatial frequencies was observed. This indicates that the regional distribution of spatial frequencies is innately determined. The size of iso-orientation domains tended to decrease as the stimulus spatial frequency increased at every age examined. In contrast, orientation representation bias changed with age. In cats younger than 3 months, the cardinal (vertical and horizontal) orientations were represented predominantly over the oblique orientations. However, in young adult cats from 3 to 9 months old, the representation bias switched to predominantly oblique orientations. These age-dependent changes in the orientation representation bias imply that orientation maps continue to elaborate within postnatal 1 year with the consolidation of spatial frequency selectivity. We conclude that both intrinsic and mutual factors lead to the development of orientation maps and spatial frequency selectivity.
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Affiliation(s)
- Toshiki Tani
- Laboratory for Visual Neurocomputing, Brain Science Institute, RIKEN, Wako, Saitama, Japan.
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14
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van de Ven V, Jans B, Goebel R, De Weerd P. Early Human Visual Cortex Encodes Surface Brightness Induced by Dynamic Context. J Cogn Neurosci 2012; 24:367-77. [DOI: 10.1162/jocn_a_00126] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Abstract
Visual scene perception owes greatly to surface features such as color and brightness. Yet, early visual cortical areas predominantly encode surface boundaries rather than surface interiors. Whether human early visual cortex may nevertheless carry a small signal relevant for surface perception is a topic of debate. We induced brightness changes in a physically constant surface by temporally modulating the luminance of surrounding surfaces in seven human participants. We found that fMRI activity in the V2 representation of the constant surface was in antiphase to luminance changes of surrounding surfaces (i.e., activity was in-phase with perceived brightness changes). Moreover, the amplitude of the antiphase fMRI activity in V2 predicted the strength of illusory brightness perception. We interpret our findings as evidence for a surface-related signal in early visual cortex and discuss the neural mechanisms that may underlie that signal in concurrence with its possible interaction with the properties of the fMRI signal.
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15
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Masuda A, Watanabe J, Terao M, Watanabe M, Yagi A, Maruya K. Awareness of Central Luminance Edge is Crucial for the Craik-O'Brien-Cornsweet Effect. Front Hum Neurosci 2011; 5:125. [PMID: 22059072 PMCID: PMC3203414 DOI: 10.3389/fnhum.2011.00125] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 10/13/2011] [Indexed: 11/13/2022] Open
Abstract
The Craik-O'Brien-Cornsweet (COC) effect demonstrates that perceived lightness depends not only on the retinal input at corresponding visual areas but also on distal retinal inputs. In the COC effect, the central edge of an opposing pair of luminance gradients (COC edge) makes adjoining regions with identical luminance appear to be different. To investigate the underlying mechanisms of the effect, we examined whether the subjective awareness of the COC edge is necessary for the generation of the effect. We manipulated the visibility of the COC edge using visual backward masking and continuous flash suppression while monitoring subjective reports regarding online percepts and aftereffects of adaptation. Psychophysical results showed that the online percept of the COC effect nearly vanishes in conditions where the COC edge is rendered invisible. On the other hand, the results of adaptation experiments showed that the COC edge is still processed at the early stage even under the perceptual suppression. These results suggest that processing of the COC edge at the early stage is not sufficient for generating the COC effect, and that subjective awareness of the COC edge is necessary.
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Affiliation(s)
- Ayako Masuda
- Department of Integrated Psychological Science, Kwansei Gakuin University Nishinomiya, Japan
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16
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Tajima S, Watanabe M. Acquisition of nonlinear forward optics in generative models: Two-stage “downside-up” learning for occluded vision. Neural Netw 2011; 24:148-58. [DOI: 10.1016/j.neunet.2010.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Revised: 10/13/2010] [Accepted: 10/14/2010] [Indexed: 10/18/2022]
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17
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Weil RS, Rees G. A new taxonomy for perceptual filling-in. ACTA ACUST UNITED AC 2010; 67:40-55. [PMID: 21059374 PMCID: PMC3119792 DOI: 10.1016/j.brainresrev.2010.10.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 10/20/2010] [Accepted: 10/31/2010] [Indexed: 11/24/2022]
Abstract
Perceptual filling-in occurs when structures of the visual system interpolate information across regions of visual space where that information is physically absent. It is a ubiquitous and heterogeneous phenomenon, which takes place in different forms almost every time we view the world around us, such as when objects are occluded by other objects or when they fall behind the blind spot. Yet, to date, there is no clear framework for relating these various forms of perceptual filling-in. Similarly, whether these and other forms of filling-in share common mechanisms is not yet known. Here we present a new taxonomy to categorize the different forms of perceptual filling-in. We then examine experimental evidence for the processes involved in each type of perceptual filling-in. Finally, we use established theories of general surface perception to show how contextualizing filling-in using this framework broadens our understanding of the possible shared mechanisms underlying perceptual filling-in. In particular, we consider the importance of the presence of boundaries in determining the phenomenal experience of perceptual filling-in.
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Affiliation(s)
- Rimona S Weil
- Wellcome Trust Centre for Neuroimaging, University College London, 12 Queen Square, London WC1N 3BG, UK.
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18
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Peters JC, Jans B, van de Ven V, De Weerd P, Goebel R. Dynamic brightness induction in V1: Analyzing simulated and empirically acquired fMRI data in a “common brain space” framework. Neuroimage 2010; 52:973-84. [DOI: 10.1016/j.neuroimage.2010.03.070] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Revised: 03/06/2010] [Accepted: 03/24/2010] [Indexed: 10/19/2022] Open
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Linking depth to lightness and anchoring within the differentiation-integration formalism. Vision Res 2010; 50:1486-500. [PMID: 20460133 DOI: 10.1016/j.visres.2010.05.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 04/29/2010] [Accepted: 05/05/2010] [Indexed: 11/22/2022]
Abstract
Recently we developed a model that reproduces the Kanizsa square illusion based on two principles: (1) a spatial 2-D integration of luminance ratio and differentiated depth signals creates a "primary" lightness map and a depth map, respectively, which is then followed by (2) a modification of the primary lightness values under influence of the perceived depth (Kogo, Strecha, Van Gool, & Wagemans, 2010). Within this model, the process of the spatial integration inevitably introduced an arbitrary offset. In order to obtain absolute values of depth and lightness, the offset values needed to be determined by other constraints. This is the anchoring problem of the depth and lightness measurements. Here we report the anchoring rules that were established by investigating the model's responses to the Kanizsa square and its wide range of variations. For the primary lightness map, the highest value rule was applied, while the area rule appeared most plausible for the depth map. By applying the same principles to simple figures consisting of black and white areas of different size ratios, the model succeeded in reproducing published empirical results on lightness anchoring (Li & Gilchrist, 1999).
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Abstract
Background The perception of brightness depends on spatial context: the same stimulus can appear light or dark depending on what surrounds it. A less well-known but equally important contextual phenomenon is that the colour of a stimulus can also alter its brightness. Specifically, stimuli that are more saturated (i.e. purer in colour) appear brighter than stimuli that are less saturated at the same luminance. Similarly, stimuli that are red or blue appear brighter than equiluminant yellow and green stimuli. This non-linear relationship between stimulus intensity and brightness, called the Helmholtz-Kohlrausch (HK) effect, was first described in the nineteenth century but has never been explained. Here, we take advantage of the relative simplicity of this ‘illusion’ to explain it and contextual effects more generally, by using a simple Bayesian ideal observer model of the human visual ecology. We also use fMRI brain scans to identify the neural correlates of brightness without changing the spatial context of the stimulus, which has complicated the interpretation of related fMRI studies. Results Rather than modelling human vision directly, we use a Bayesian ideal observer to model human visual ecology. We show that the HK effect is a result of encoding the non-linear statistical relationship between retinal images and natural scenes that would have been experienced by the human visual system in the past. We further show that the complexity of this relationship is due to the response functions of the cone photoreceptors, which themselves are thought to represent an efficient solution to encoding the statistics of images. Finally, we show that the locus of the response to the relationship between images and scenes lies in the primary visual cortex (V1), if not earlier in the visual system, since the brightness of colours (as opposed to their luminance) accords with activity in V1 as measured with fMRI. Conclusions The data suggest that perceptions of brightness represent a robust visual response to the likely sources of stimuli, as determined, in this instance, by the known statistical relationship between scenes and their retinal responses. While the responses of the early visual system (receptors in this case) may represent specifically the statistics of images, post receptor responses are more likely represent the statistical relationship between images and scenes. A corollary of this suggestion is that the visual cortex is adapted to relate the retinal image to behaviour given the statistics of its past interactions with the sources of retinal images: the visual cortex is adapted to the signals it receives from the eyes, and not directly to the world beyond.
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Affiliation(s)
- David Corney
- UCL Institute of Ophthalmology, London, United Kingdom
| | - John-Dylan Haynes
- Bernstein Centre for Computational Neuroscience Berlin, Berlin, Germany
| | - Geraint Rees
- UCL Institute of Cognitive Neuroscience, London, United Kingdom
- Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom
| | - R. Beau Lotto
- UCL Institute of Ophthalmology, London, United Kingdom
- * E-mail:
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Salmela VR, Laurinen PI. Low-level features determine brightness in White's and Benary's illusions. Vision Res 2009; 49:682-90. [PMID: 19200439 DOI: 10.1016/j.visres.2009.01.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 11/28/2008] [Accepted: 01/07/2009] [Indexed: 11/18/2022]
Abstract
We masked White's and Benary's brightness illusions and simultaneous contrast with narrowband visual noise and measured detection thresholds and brightness. The noise was either isotropic or orientation filtered. A narrow spatial frequency tuning was found for detection and brightness for every stimulus. A narrow orientation tuning was also found: the strength of the illusions decreased (White and Benary) or increased (White) depending on the orientation of the mask. The critical borders were always of the same contrast polarity. The results suggest that the brightness in figure-ground scenes is determined by mechanisms integrating incremental and decremental borders in early visual cortices.
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Affiliation(s)
- Viljami R Salmela
- Department of Psychology, University of Helsinki, P.O. Box 9, Siltavuorenpenger 20 D, 00014 Helsinki, Finland.
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22
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Lu HD, Chen G, Ts'o DY, Roe AW. A rapid topographic mapping and eye alignment method using optical imaging in Macaque visual cortex. Neuroimage 2008; 44:636-46. [PMID: 19013530 DOI: 10.1016/j.neuroimage.2008.10.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2007] [Revised: 06/10/2008] [Accepted: 10/06/2008] [Indexed: 10/21/2022] Open
Abstract
In optical imaging experiments, it is often advantageous to map the field of view and to converge the eyes without electrophysiological recording. This occurs when limited space precludes placement of an electrode or in chronic optical chambers in which one may not want to introduce an electrode each session or for determining eye position in studies of ocular disparity response in visual cortex of anesthetized animals. For these purposes, we have developed a spot imaging method that can be conducted rapidly and repeatedly throughout an experiment. Using small 0.2 degrees -0.5 degrees spots, the extent of the imaged field of view is mapped by imaging cortical response to single spots, placed at different positions (0.2 degrees steps) in either the horizontal or vertical axes. By shifting the relative positions of two spots, one presented to each eye, eye convergence can be assessed to within 0.1 degrees resolution. Once appropriate eye alignment is determined, stimuli for further optical imaging procedures (e.g. imaging random dot stimuli for study of disparity responses) can then be confidently placed. This procedure can be quickly repeated throughout the experiment to ensure maintained eye alignment.
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Affiliation(s)
- H D Lu
- Dept of Psychology, 301 Wilson Hall, Vanderbilt University, Nashville, TN 37212, USA
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23
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Metacontrast masking and the cortical representation of surface color: dynamical aspects of edge integration and contrast gain control. Adv Cogn Psychol 2008; 3:327-47. [PMID: 20517518 PMCID: PMC2864963 DOI: 10.2478/v10053-008-0034-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2006] [Accepted: 09/30/2006] [Indexed: 11/20/2022] Open
Abstract
This paper reviews recent theoretical and experimental work supporting the idea
that brightness is computed in a series of neural stages involving edge
integration and contrast gain control. It is proposed here that metacontrast and
paracontrast masking occur as byproducts of the dynamical properties of these
neural mechanisms. The brightness computation model assumes, more specifically,
that early visual neurons in the retina, and cortical areas V1 and V2, encode
local edge signals whose magnitudes are proportional to the logarithms of the
luminance ratios at luminance edges within the retinal image. These local edge
signals give rise to secondary neural lightness and darkness spatial induction
signals, which are summed at a later stage of cortical processing to produce a
neural representation of surface color, or achromatic color, in the case of the
chromatically neutral stimuli considered here. Prior to the spatial summation of
these edge-based induction signals, the weights assigned to local edge contrast
are adjusted by cortical gain mechanisms involving both lateral interactions
between neural edge detectors and top-down attentional control. We have
previously constructed and computer-simulated a neural model of achromatic color
perception based on these principles and have shown that our model gives a good
quantitative account of the results of several brightness matching experiments.
Adding to this model the realistic dynamical assumptions that 1) the neurons
that encode local contrast exhibit transient firing rate enhancement at the
onset of an edge, and 2) that the effects of contrast gain control take time to
spread between edges, results in a dynamic model of brightness computation that
predicts the existence Broca-Sulzer transient brightness enhancement of the
target, Type B metacontrast masking, and a form of paracontrast masking in which
the target brightness is enhanced when the mask precedes the target in time.
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25
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Hung CP, Ramsden BM, Roe AW. A functional circuitry for edge-induced brightness perception. Nat Neurosci 2007; 10:1185-90. [PMID: 17704775 DOI: 10.1038/nn1948] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Accepted: 06/28/2007] [Indexed: 11/10/2022]
Abstract
The identification of visual contours and surfaces is central to visual scene segmentation. One view of image construction argues that object contours are first identified and then surfaces are filled in. Although there are psychophysical and single-unit data to suggest that the filling-in view is correct, the underlying circuitry is unknown. Here we examine specific spike-timing relationships between border and surface responses in cat visual cortical areas 17 and 18. With both real and illusory (Cornsweet) brightness contrast stimuli, we found a border-to-surface shift in the relative timing of spike activity. This shift was absent when borders were absent and could be reversed with relocation of the stimulus border, indicating that the direction of information flow is highly dependent on stimulus conditions. Furthermore, this effect was seen predominantly in 17-18, and not 17-17, interactions. These results demonstrate a border-to-surface mechanism at early stages of visual processing and emphasize the importance of interareal circuitry in vision.
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Affiliation(s)
- Chou P Hung
- Institute of Neuroscience and Brain Research Center, 155 Sec. 2 Li-Nong St., National Yang Ming University, Taipei 112, Taiwan
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26
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Rudd ME, Zemach IK. Contrast polarity and edge integration in achromatic color perception. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2007; 24:2134-56. [PMID: 17621319 DOI: 10.1364/josaa.24.002134] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Previous work has shown that the achromatic color of a target patch embedded in simple two-dimensional display depends not only on the luminance contrast between the target and its immediate surround but also on the contrasts of other nearby edges. Quantitative models have been proposed in which the target color is modeled as a spatially weighted sum of edge contrasts in which the target edge receives the largest weight. Rudd and Arrington [Vision Res.41, 3649 (2001)] elaborated on this idea to include an additional mechanism whereby effects of individual color-inducing edges are "partially blocked" by edges lying along the path between the inducing edge and the target. We tested the blockage model in appearance matching experiments performed with disk-and-single-ring stimuli having all four possible combinations of inner and outer ring edge contrast polarities. Evidence was obtained for both "blockage" (attenuation) and "antiblockage" (amplification) of achromatic color induction signals, depending on the contrast polarities of the inner and outer ring edges. A neural model is proposed to account for our data on the basis of the contrast gain control occurring between cortical edge detector neurons.
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Affiliation(s)
- Michael E Rudd
- Howard Hughes Medical Institute and Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA.
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27
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Salmela VR, Laurinen PI. Brightness processing in the visual cortex. Neurosci Lett 2007; 420:160-2. [PMID: 17512119 DOI: 10.1016/j.neulet.2007.04.068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Revised: 04/28/2007] [Accepted: 04/30/2007] [Indexed: 10/23/2022]
Abstract
Single cell recordings have shown that some cells in the primary visual cortex (V1) signal surface brightness. However, fMRI experiments have found brightness related activation only in the higher cortical areas. In a psychophysical setup, we were able to dissociate the reduction of brightness caused by Gabor flankers, similar to the receptive fields in V1, from the edge induced brightness change. The former resemble the single cell recording results and the latter the fMRI results.
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28
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Salmela VR, Laurinen PI. Spatial frequency difference between textures interferes with brightness perception. Vision Res 2007; 47:452-9. [PMID: 17239917 DOI: 10.1016/j.visres.2006.11.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Revised: 11/24/2006] [Accepted: 11/30/2006] [Indexed: 11/30/2022]
Abstract
Abrupt changes in luminance trigger and restrict brightness filling-in. If brightness was actively filled-in and mediated by cells signaling both luminance borders and surface brightness, then brightness spreading could also get disrupted by changes in texture. We measured psychophysically the brightness of a uniform luminance disk, which was segmented into two parts by different textures. The brightness of the central part of the disk was substantially reduced, and the reduction depended on spatial frequency, but not on the orientation difference between the textures. The results show that texture borders are able to block brightness filling-in. The bandwidth of brightness spreading was estimated to be approximately 1.5 octaves. This suggests that brightness information spreads only between neurons of similar spatial frequency characteristics.
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Affiliation(s)
- Viljami R Salmela
- Department of Psychology, PO Box 9 (Siltavuorenpenger 20 D), University of Helsinki, Helsinki 00014, Finland.
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29
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Abstract
Our studies on brightness information processing in Macaque monkey visual cortex suggest that the thin stripes in the secondary visual area (V2) are preferentially activated by brightness stimuli (such as full field luminance modulation and illusory edge-induced brightness modulation). To further examine this possibility, we used intrinsic signal optical imaging to examine contrast response of different functional domains in primary and secondary visual areas (V1 and V2). Color and orientation stimuli were used to map functional domains in V1 (color domains, orientation domains) and V2 (thin stripes, thick/pale stripes). To examine contrast response, sinusoidal gratings at different contrasts and spatial frequencies were presented. We find that, consistent with previous studies, the optical signal increased systematically with contrast level. Unlike single-unit responses, optical signals for both color domains and orientation domains in V1 exhibit linear contrast response functions, thereby providing a large dynamic range for V1 contrast response. In contrast to domains in V1, domains in V2 exhibit nonlinear responses, characterized by high gain at low contrasts, saturating at a mid-high contrast levels. At high contrasts, thin stripes exhibit increasing response, whereas thick/pale stripes saturate, consistent with a strong parvocellular input to thin stripes. These findings suggest that, with respect to contrast encoding, thin stripes have a larger dynamic range than thick/pale stripes and further support a role for thin stripes in processing of brightness information.
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Affiliation(s)
- Haidong D Lu
- Department of Psychology, Vanderbilt University, Nashville, TN 37203, USA.
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30
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Liang Z, Shen W, Shou T. Enhancement of oblique effect in the cat's primary visual cortex via orientation preference shifting induced by excitatory feedback from higher-order cortical area 21a. Neuroscience 2007; 145:377-83. [PMID: 17223276 DOI: 10.1016/j.neuroscience.2006.11.051] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Revised: 11/08/2006] [Accepted: 11/22/2006] [Indexed: 11/15/2022]
Abstract
It is often suggested that the oblique effect, the well-known phenomenon whereby both humans and animals are visually more sensitive to vertical and horizontal contours than to oblique ones, is due to the overrepresentation of cardinal orientations in the visual cortex. The functional role of feedback projections from higher-order cortical areas to lower-order areas is not fully understood. Combining the two issues in a study using optical imaging here, we report that the neural oblique effect was significantly enhanced (3.7 times higher than the normal) in the cat's primary visual cortex through orientation shifting induced by excitatory feedback from the higher-order cortical area 21a. This suggests that a reciprocal co-excitatory mechanism may underlie the perceptual oblique effect.
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Affiliation(s)
- Z Liang
- Vision Research Laboratory, Center for Brain Science Research, School of Life Sciences, 220 Handan Road, Fudan University, Shanghai 200433, PR China
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31
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Sakai K, Nishimura H. Surrounding suppression and facilitation in the determination of border ownership. J Cogn Neurosci 2006; 18:562-79. [PMID: 16768360 DOI: 10.1162/jocn.2006.18.4.562] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Contextual modulation reported in early- to intermediate-level visual areas could be an essential component to signal border ownership (BO) that specifies the direction of figure along a contour. The surrounding regions that evoke significant suppression or facilitation are highly localized and asymmetric with respect to the center of the classical receptive field (CRF). We propose a hypothesis that such surrounding modulation is a basis for BO-selectivity. Although this idea has been discussed for several years, it is uncertain how many of a vast variety of surrounding organizations could signal correctly the direction of ownership, and how many could signal consistently for various stimuli. We carried out computationally a population study of the surrounding effects to investigate how many cells exhibit effective and consistent BO signals. We tested hundreds of various organizations, and found that most of the asymmetric, iso-orientation suppressive regions, regardless of position or size, lead to surprisingly high consistency in the direction of ownership for various stimuli. The combinations of iso-orientation suppression and cross-orientation facilitation indicate both high robustness and consistency in the ownership determination. We constructed a model for BO-selective neurons based on the surrounding effects, and investigated whether the model reproduces major characteristics of the neuronal responses, including a variety in the BO selectivity among neurons, consistency with respect to various stimuli, invariance to stimulus size, and co-selectivity to BO and contrast. The model reproduced successfully the major characteristics of BO-selective neurons.
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33
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Shen W, Liang Z, Chen X, Shou T. Posteromedial lateral suprasylvian motion area modulates direction but not orientation preference in area 17 of cats. Neuroscience 2006; 142:905-16. [PMID: 16890373 DOI: 10.1016/j.neuroscience.2006.06.046] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Revised: 06/22/2006] [Accepted: 06/23/2006] [Indexed: 11/24/2022]
Abstract
In visual cortices of cats there are two major, largely parallel, feedforward processing streams which conduct visual information from the primary visual cortices to the parietal and temporal visual cortices, processing motion and form information, respectively. In addition to the feedforward streams, there exist many feedback projections from higher-order visual cortices to lower-order visual cortices. Using the intrinsic signal optical imaging, this study has examined the influence of feedback signals originating from area posteromedial lateral suprasylvian (PMLS), the dominant motion-processing region of the parietal cortex, on responses of neurons, orientational maps, and directional maps in cats' area 17 (striate cortex). The inactivation of area PMLS by local application of GABA resulted in the reduction of the magnitude of responses of area 17 cells though area 17 of the cat is mainly involved in form information processing rather than motion. Furthermore, inactivation of area PMLS abolished the global layout of direction maps in area 17 but did not affect the basic structure of the orientation maps in area 17. Thus, it appears that higher-order cortical areas along one information processing stream may exert cross-stream modulatory effects on fundamental properties of neurons located in the lower-order areas along distinct information processing streams.
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Affiliation(s)
- W Shen
- Vision Research Laboratory, Center for Brain Science Research, School of Life Sciences, Fudan University, Shanghai 200433, PR China
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34
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Cornelissen FW, Wade AR, Vladusich T, Dougherty RF, Wandell BA. No functional magnetic resonance imaging evidence for brightness and color filling-in in early human visual cortex. J Neurosci 2006; 26:3634-41. [PMID: 16597716 PMCID: PMC6674117 DOI: 10.1523/jneurosci.4382-05.2006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The brightness and color of a surface depends on its contrast with nearby surfaces. For example, a gray surface can appear very light when surrounded by a black surface or dark when surrounded by a white surface. Some theories suggest that perceived surface brightness and color is represented explicitly by neural signals in cortical visual field maps; these neural signals are not initiated by the stimulus itself but rather by the contrast signals at the borders. Here, we use functional magnetic resonance imaging (fMRI) to search for such neural "filling-in" signals. Although we find the usual strong relationship between local contrast and fMRI response, when perceived brightness or color changes are induced by modulating a surrounding field, rather than the surface itself, we find there is no corresponding local modulation in primary visual cortex or other nearby retinotopic maps. Moreover, when we model the obtained fMRI responses, we find strong evidence for contributions of both local and long-range edge responses. We argue that such extended edge responses may be caused by neurons previously identified in neurophysiological studies as being brightness responsive, a characterization that may therefore need to be revised. We conclude that the visual field maps of human V1 and V2 do not contain filled-in, topographical representations of surface brightness and color.
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Affiliation(s)
- Frans W Cornelissen
- NeuroImaging Centre, School of Behavioural and Cognitive Neurosciences, University Medical Centre Groningen, University of Groningen, Groningen 9700 RB, The Netherlands.
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35
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Imamura K, Tanaka S, Ribot J, Kobayashi M, Yamamoto M, Nakadate K, Watanabe Y. Preservation of functional architecture in visual cortex of cats with experimentally induced hydrocephalus. Eur J Neurosci 2006; 23:2087-98. [PMID: 16630056 DOI: 10.1111/j.1460-9568.2006.04729.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We investigated how neural function is preserved or matured in the visual cortex of cats, following the induction of hydrocephalus by kaolin injection. In vivo optical imaging of intrinsic signals in 11-17-week-old hydrocephalic cats revealed orientation maps showing the orderly arrangement of preferred orientations when stimulated by grating stimuli at a low spatial frequency, whereas stimulus-evoked intrinsic signals in response to gratings at a high spatial frequency were often too weak to construct orientation maps. Furthermore, in two of the three hydrocephalic cats, initially deteriorated orientation maps became almost regular maps in the second imaging experiments conducted 8 and 11 weeks, respectively, after the first imaging. This indicates that, despite large structural deformation of the hydrocephalic brain, orientation maps are elaborated sufficiently after the age of 5-6 months, by which time the orientation map formation is usually completed in normal cats. Single unit recording from the decompressed visual cortex revealed that many neurons showed normal orientation selectivity, whereas the binocularity of these neurons was found to be reduced. These results suggested that the deformed visual cortex of hydrocephalic cats exhibits a high plasticity, retaining its functional organization.
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Affiliation(s)
- Kazuyuki Imamura
- Laboratory for Visual Neurocomputing, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
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Wang Y, Xiao Y, Felleman DJ. V2 thin stripes contain spatially organized representations of achromatic luminance change. ACTA ACUST UNITED AC 2006; 17:116-29. [PMID: 16467565 DOI: 10.1093/cercor/bhj131] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
A considerable amount of research over the last decades has focused on the apparent specialization of V2 thin stripes for the processing of color in diurnal primates. However, because V2 thin stripes are functionally heterogeneous in that they consist of largely separate color- and luminance-preferring domains and because the color-preferring domains contain a systematic representation of hue, we hypothesized that they contained functional maps that subserve luminance processing. Here we show, using optical imaging of intrinsic cortical signals and microelectrode recording, that the V2 thin stripe luminance-preferring domains contain spatially segregated modules that encode the direction of relative luminance change. Quantitative analysis of the cortical responses to luminance increments or decrements indicates that these luminance-sensitive modules also encode the magnitude of the luminance change by the magnitude of the evoked cortical response. These results demonstrate an important role of V2 thin stripes in the processing of luminance and thus suggest that thin stripes are involved in the overall processing of the surface properties of objects rather than simply the processing of color.
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Affiliation(s)
- Yi Wang
- Department of Neurobiology and Anatomy, University of Texas Medical School-Houston, Houston, TX 77030, USA
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37
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Vladusich T, Lucassen MP, Cornelissen FW. Do cortical neurons process luminance or contrast to encode surface properties? J Neurophysiol 2005; 95:2638-49. [PMID: 16381807 DOI: 10.1152/jn.01016.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
On the one hand, contrast signals provide information about surface properties, such as reflectance, and patchy illumination conditions, such as shadows. On the other hand, processing of luminance signals may provide information about global light levels, such as the difference between sunny and cloudy days. We devised models of contrast and luminance processing, using principles of logarithmic signal coding and half-wave rectification. We fit each model to individual response profiles obtained from 67 surface-responsive macaque V1 neurons in a center-surround paradigm similar to those used in human psychophysical studies. The most general forms of the luminance and contrast models explained, on average, 73 and 87% of the response variance over the sample population, respectively. We used a statistical technique, known as Akaike's information criterion, to quantify goodness of fit relative to number of model parameters, giving the relative probability of each model being correct. Luminance models, having fewer parameters than contrast models, performed substantially better in the vast majority of neurons, whereas contrast models performed similarly well in only a small minority of neurons. These results suggest that the processing of local and mean scene luminance predominates over contrast integration in surface-responsive neurons of the primary visual cortex. The sluggish dynamics of luminance-related cortical activity may provide a neural basis for the recent psychophysical demonstration that luminance information dominates brightness perception at low temporal frequencies.
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Affiliation(s)
- Tony Vladusich
- Laboratory of Experimental Ophthalmology and NeuroImaging Centre, School of Behavioural and Cognitive Neurosciences, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
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38
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Perna A, Tosetti M, Montanaro D, Morrone MC. Neuronal mechanisms for illusory brightness perception in humans. Neuron 2005; 47:645-51. [PMID: 16129395 DOI: 10.1016/j.neuron.2005.07.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Revised: 04/17/2005] [Accepted: 07/12/2005] [Indexed: 10/25/2022]
Abstract
Biological visual systems are extraordinarily capable of recovering the shape and brightness of objects from sparse and fragmentary information. Using functional magnetic imaging, we show that two associative areas of the dorsal pathway--in the caudal region of the intrapariatal sulcus and in the lateral occipital sulcus--respond specifically to the Craik-O'Brien-Cornsweet illusion generated by high-pass filtered edges. Other visual areas, including primary visual cortex, also respond strongly to the retinotopic location of the edge, but these areas respond equally well to a line of matched contrast and detectability, rather than specifically to the brightness illusion. The reconstruction of surface and/or its brightness seems to be achieved by associative areas from the information about visual features provided by the primary visual cortices, even where there is no physical difference in luminance.
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Affiliation(s)
- Andrea Perna
- Scuola Normale Superiore, via Moruzzi 1, 56127 Pisa, Italy
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39
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Salmela VR, Laurinen PI. Spatial frequency tuning of brightness polarity identification. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2005; 22:2239-45. [PMID: 16277292 DOI: 10.1364/josaa.22.002239] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Recent studies have shown that cells in the primary visual cortex can, in addition to borders, also encode surface brightness. Whether the brightness is encoded by a large extraclassical receptive field or by a filling-in type mechanism activated by the luminance border is not known. These explanations imply different spatial frequency tunings for the underlying mechanism. In a psychophysical masking paradigm we measured spatial frequency tuning functions for identification of both luminance polarity (bright/dark) and luminance border orientation of oval and circular luminance patches with variable diameters (0.2-10 deg). For both tasks we obtained nearly overlapping narrow (1.5 octave) bandpass masking tuning functions centered at 1.5-5.0 c/deg. Stimulus size and shape had only minimal effect on the tuning functions. The results favor the idea of brightness filling-in and suggest that the cells activated by the luminance border modulate the activity of the cells signaling surface brightness. Further, the brightness processing mechanism is spatial frequency selective.
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Boucard CC, van Es JJ, Maguire RP, Cornelissen FW. Functional magnetic resonance imaging of brightness induction in the human visual cortex. Neuroreport 2005; 16:1335-8. [PMID: 16056135 DOI: 10.1097/01.wnr.0000175242.05343.50] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A grey surface on a bright background appears to be darker than the same surface on a dark background. We used functional magnetic resonance imaging to study this phenomenon called brightness induction. While being scanned, participants viewed centre-surround displays in which either centre or surround luminance was modulated in time. In both cases, participants perceive similar brightness changes in the central surface. In the region of the visual cortex encoding this central surface, both modulations evoked comparable functional magnetic resonance imaging responses. However, the surround modulation signal showed a considerable delay relative to the onset of the brightness percept. This suggests that, although correlated, the functional magnetic resonance imaging signals do not bear a direct relationship with perceived brightness. We conclude that retinotopically organized visual cortex does not represent brightness per se.
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Affiliation(s)
- Christine C Boucard
- Laboratory for Experimental Ophthalmology, University of Groningen, postbus 30001, 9700 RB Groningen, The Netherlands.
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41
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Abstract
Several brightness illusions indicate that borders can affect the perception of surfaces dramatically. In the Cornsweet illusion, two equiluminant surfaces appear to be different in brightness because of the contrast border between them. Here, we report the existence of cells in monkey visual cortex that respond to such an "illusory" brightness. We find that luminance responsive cells are located in color-activated regions (cytochrome oxidase blobs and bridges) of primary visual cortex (V1), whereas Cornsweet responsive cells are found preferentially in the color-activated regions (thin stripes) of second visual area (V2). This colocalization of brightness and color processing within V1 and V2 suggests a segregation of contour and surface processing in early visual pathways and a hierarchy of brightness information processing from V1 to V2 in monkeys.
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Affiliation(s)
- Anna Wang Roe
- Department of Psychology, 301 Wilson Hall, Vanderbilt University, Nashville, TN 37203, USA.
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Huang L, Chen X, Shou T. Spatial frequency-dependent feedback of visual cortical area 21a modulating functional orientation column maps in areas 17 and 18 of the cat. Brain Res 2004; 998:194-201. [PMID: 14751590 DOI: 10.1016/j.brainres.2003.11.024] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The feedback effect of activity of area 21a on orientation maps of areas 17 and 18 was investigated in cats using intrinsic signal optical imaging. A spatial frequency-dependent decrease in response amplitude of orientation maps to grating stimuli was observed in areas 17 and 18 when area 21a was inactivated by local injection of GABA, or by a lesion induced by liquid nitrogen freezing. The decrease in response amplitude of orientation maps of areas 17 and 18 after the area 21a inactivation paralleled the normal response without the inactivation. Application in area 21a of bicuculline, a GABAa receptor antagonist caused an increase in response amplitude of orientation maps of area 17. The results indicate a positive feedback from high-order visual cortical area 21a to lower-order areas underlying a spatial frequency-dependent mechanism.
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Affiliation(s)
- Luoxiu Huang
- Vision Research Laboratory and Liren Laboratory, Center for Brain Science Research, School of Life Sciences, Fudan University, Shanghai 200433, PR China
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Eagleman DM, Jacobson JE, Sejnowski TJ. Perceived luminance depends on temporal context. Nature 2004; 428:854-6. [PMID: 15085147 PMCID: PMC2927826 DOI: 10.1038/nature02467] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Accepted: 03/04/2004] [Indexed: 11/08/2022]
Abstract
Brightness--the perception of an object's luminance--arises from complex and poorly understood interactions at several levels of processing. It is well known that the brightness of an object depends on its spatial context, which can include perceptual organization, scene interpretation, three-dimensional interpretation, shadows, and other high-level percepts. Here we present a new class of illusion in which temporal relations with spatially neighbouring objects can modulate a target object's brightness. When compared with a nearby patch of constant luminance, a brief flash appears brighter with increasing onset asynchrony. Simultaneous contrast, retinal effects, masking, apparent motion and attentional effects cannot account for this illusory enhancement of brightness. This temporal context effect indicates that two parallel streams--one adapting and one non-adapting--encode brightness in the visual cortex.
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Affiliation(s)
- David M Eagleman
- Department of Neurobiology and Anatomy, University of Texas, Houston Medical School, 6431 Fannin Street, Suite 7.046, Houston, Texas 77030, USA.
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Haynes JD, Lotto RB, Rees G. Responses of human visual cortex to uniform surfaces. Proc Natl Acad Sci U S A 2004; 101:4286-91. [PMID: 15010538 PMCID: PMC384733 DOI: 10.1073/pnas.0307948101] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Surface perception is fundamental to human vision, yet most studies of visual cortex have focused on the processing of borders. We therefore investigated the responses of human visual cortex to parametric changes in the luminance of uniform surfaces by using functional MRI. Early visual areas V1 and V2/V3 showed strong and reliable increases in signal for both increments and decrements in surface luminance. Responses were significantly larger for decrements than for increments, which was fully accounted for by differences in retinal illumination arising from asymmetric pupil dynamics. Responses to both sustained and transient changes of illumination were transient. Signals in early visual cortex scaled linearly with the magnitude of change in retinal illumination, as did subjects' subjective ratings of the perceived brightness of the stimuli. Our findings show that early visual cortex responds strongly to surfaces and that perception of surface brightness is compatible with brain responses at the earliest cortical stages of processing.
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Affiliation(s)
- John-Dylan Haynes
- Institute of Cognitive Neuroscience, University College London, Alexandra House, 17 Queen Square, London WC1N 3AR, United Kingdom.
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Tani T, Yokoi I, Ito M, Tanaka S, Komatsu H. Functional organization of the cat visual cortex in relation to the representation of a uniform surface. J Neurophysiol 2003; 89:1112-25. [PMID: 12574484 DOI: 10.1152/jn.00478.2002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neuronal activity in the early visual cortex has been extensively studied from the standpoint of contour representation. On the other hand, representation of the interior of a surface surrounded by a contour is much less well understood. Several studies have identified neurons activated by a uniform surface covering their receptive fields, but their distribution within the cortex is not yet known. The aim of the present study was to obtain a better understanding of the distribution of such neurons in the visual cortex. Using optical imaging of intrinsic signals, we found that there are a group of surface-responsive regions located in area 18, along the area 17/18 border, that tend to overlap the singular points of the orientation-preference map. Extracellular recordings confirmed that neurons responsive to uniform plane stimuli are accumulated in these regions. Such neurons also existed outside the surface-responsive regions around the singular points. These results suggest that there exists a functional organization related to the representation of a uniform surface in the early visual cortex.
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Affiliation(s)
- Toshiki Tani
- Laboratory of Neural Control, National Institute for Physiological Sciences, Okazaki-shi, Aichi, 444-8585, 351-0198, Japan
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46
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Abstract
Recent physiological studies show that neural responses correlated with the perception of brightness are found in cortical area V1 but not earlier in the visual pathway (Kayama et al., 1979; Reid and Shapley, 1989; Squatrito et al., 1990; Komatsu et al., 1996; Rossi et al., 1996; MacEvoy et al., 1998; Rossi and Paradiso, 1999; Hung et al., 2001; Kinoshita and Komatsu, 2001; MacEvoy and Paradiso, 2001). However, these studies are based on comparisons of neural responses in animals with brightness perception in humans. Very little is known about the perception of brightness in animals typically used in physiological experiments. In this study, we quantify brightness discrimination, brightness induction, and White's effect in macaque monkeys. The results show that, qualitatively and quantitatively, the perception of brightness in macaques and humans is quite similar. This similarity may be an indication of common underlying neural computations in the two species.
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Gawne TJ, Martin JM. Responses of primate visual cortical neurons to stimuli presented by flash, saccade, blink, and external darkening. J Neurophysiol 2002; 88:2178-86. [PMID: 12424259 DOI: 10.1152/jn.00151.200] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our visual experience constitutes an unending chain of transient events, including those caused by saccadic eye movements, by blinks, and by localized or global changes in the external world. The categorical perception of objects is maintained across different classes of transient events, suggesting that the neural circuitry underlying visual perception responds to different transient events in a similar manner. However, different sorts of transients do have different perceptual impacts: for example, the sudden changes in a scene due to a saccade or a blink do not disturb our perceptual continuity of a visual scene as much as an external change does. We recorded the responses of 103 single visual cortical neurons in two rhesus monkeys (V1: n = 38, V2: n = 19, V3V/VP: n = 30, V4V: n = 16) to the onset and offset of a visual stimulus that was elicited by four different conditions: 1) stimulus flashed on and off while the eyes remain fixed; 2) stimulus turned on and off along with the entire scene (external darkening); 3) stimulus constant, onset and offset induced by rapid saccadic eye movements; and 4) offset induced by an eyeblink. For most neurons the onset and offset of a visual stimulus elicited qualitatively similar responses regardless of condition. We found no systematic effect of different conditions across the neuronal population. Previously we have shown that when the visual scene is occluded by a blink V1 neuronal firing declines in a similar manner as when the external scene is darkened and the eyes left open. Here we show that this is also the case in V2, V3V/VP, and V4V. However, for a substantial minority of neurons, the response varied strongly as a function of the transient event. This overall pattern was the same in all four cortical areas studied here. We hypothesize that most neurons in visual cortex constitute a passive "filter bank", analyzing the scene for specific details regardless of condition. However, there are neurons that respond in a qualitatively different manner depending on how a stimulus is presented, and we hypothesize that these signals may be important for determining the perceptual salience of a visual event.
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Affiliation(s)
- Timothy J Gawne
- Department of Physiological Optics, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
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Abstract
The visual image formed on the retina represents an amalgam of visual scene properties, including the reflectances of surfaces, their relative positions, and the type of illumination. The challenge facing the visual system is to extract the "meaning" of the image by decomposing it into its environmental causes. For each local region of the image, that extraction of meaning is only possible if information from other regions is taken into account. Of particular importance is a set of image cues revealing surface occlusion and/or lighting conditions. These information-rich cues direct the perceptual interpretation of other more ambiguous image regions. This context-dependent transformation from image to perception has profound-but frequently under-appreciated-implications for neurophysiological studies of visual processing: To demonstrate that neuronal responses are correlated with perception of visual scene properties, rather than visual image features, neuronal sensitivity must be assessed in varied contexts that differentially influence perceptual interpretation. We review a number of recent studies that have used this context-based approach to explore the neuronal bases of visual scene perception.
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Affiliation(s)
- Thomas D Albright
- Howard Hughes Medical Institute, Systems Neurobiology Laboratories, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
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49
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Hung CP, Ramsden BM, Roe AW. Weakly modulated spike trains: significance, precision, and correction for sample size. J Neurophysiol 2002; 87:2542-54. [PMID: 11976390 DOI: 10.1152/jn.00420.2001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many single-unit electrophysiological studies of visual cortex have investigated strong evoked responses to simple stimuli such as oriented gratings. Experiments involving other types of stimuli, such as natural scenes, higher-order features, and surface brightness, produce single-unit responses that are more difficult to interpret. Experiments with brightness, in particular, evoke single-unit responses that are typically weakly modulated. When the brightness is generated by a visual illusion such as the Cornsweet illusion, statistical tests are often necessary to distinguish true responses from baseline fluctuations. Here, using data collected from cat Areas 17 and 18 in response to real and illusory brightness stimuli, we provide a method for detecting and quantifying weak but significant periodic responses. By randomizing spike trains (via bootstrap methods), we provide confidence levels for response significance, permitting the evaluation of both weak and strong responses. We show that because of a strong dependence on total spike number, response significance can only be appropriately determined with randomized spike trains of similar spike number. Such randomizations can be performed for both stimulus-elicited and spontaneously occurring spike trains. By developing a method for generating randomized modulated spike trains (phase-restricted randomization) from actual recordings, we calculate upper and lower confidence limits of modulated spike trains and describe how measurement precision varies as a function of total spike count. Finally, using this randomization method, we describe how a correction function can be determined to correct for measurement bias introduced at low spike counts. These methods may also be useful in the study of small but potentially significant responses in other systems.
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Affiliation(s)
- Chou P Hung
- Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut 06520-8001, USA
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