Document Detail

Effect of background colors on the tuning of color-selective cells in monkey area V4.
MedLine Citation:
PMID:  16617176     Owner:  NLM     Status:  MEDLINE    
When objects are viewed in different illuminants, their color does not change or changes little in spite of significant changes in the wavelength composition of the light reflected from them. In previous studies, we have addressed the physiology underlying this color constancy by recording from cells in areas V1, V2, and V4 of the anesthetized monkey. Truly color-coded cells, ones that respond to a patch of a given color irrespective of the wavelength composition of the light reflected from it, were only found in area V4. In the present study, we have used a different approach to test the responses of V4 cells in both anesthetized and awake behaving monkeys. Stimuli of different colors, embedded within a Mondrian-type multicolored background, were used to identify the chromatic selectivity of neurons. The illumination of the background was then varied, and the tuning of V4 neurons was tested again for each background illumination. With anesthetized monkeys, the psychophysical effect of changing background illumination was inferred from our own experience, whereas in the awake behaving animal, it was directly reported by the monkey. We found that the majority of V4 neurons shifted their color-tuning profile with each change in the background illumination: each time the color of the background on the computer screen was changed so as to simulate a change in illumination, cells shifted their color-tuning function in the direction of the chromaticity component that had been increased. A similar shift was also observed in colored match-to-sample psychometric functions of both human and monkey. The shift in monkey psychometric functions was quantitatively equivalent to the shift in the responses of the corresponding population of cells. We conclude that neurons in area V4 exhibit the property of color constancy and that their response properties are thus able to reflect color perception.
Makoto Kusunoki; Konstantinos Moutoussis; Semir Zeki
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of neurophysiology     Volume:  95     ISSN:  0022-3077     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  2006 May 
Date Detail:
Created Date:  2006-04-17     Completed Date:  2006-06-28     Revised Date:  2007-08-13    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3047-59     Citation Subset:  IM    
Wellcome Laboratory of Neurobiology, University College London, London WC1E 6BT, UK.
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MeSH Terms
Action Potentials / physiology
Analysis of Variance
Brain Mapping
Color Perception / physiology*
Macaca fascicularis
Neurons / classification,  physiology*
Photic Stimulation / methods
Sensory Thresholds / physiology
Visual Cortex / cytology*
Visual Fields / physiology*
Wakefulness / physiology
Grant Support
//Wellcome Trust

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