The Journal of Neuroscience, October 18, 2006, 26(42):10826-10846; doi:10.1523/JNEUROSCI.2091-06.2006
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Behavioral/Systems/Cognitive
Spatial and Temporal Properties of Cone Signals in Alert Macaque Primary Visual Cortex
Bevil R. Conway1,2 and
Margaret S. Livingstone1
1Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, and 2Wellesley College, Wellesley, Massachusetts 02481
Correspondence should be addressed to Bevil R. Conway, Department of Neurobiology, Harvard Medical School, Boston, MA 02115. Email: bconway{at}hms.harvard.edu
Neurons in the lateral geniculate nucleus cannot perform the spatial color calculations necessary for color contrast and color constancy. Under neutral-adapting conditions, we mapped the cone inputs (L, M, and S) to 83 cone-opponent cells representing the central visual field of the next stage of visual processing, primary visual cortex (V1), to determine how the color signals are spatially transformed. Cone-opponent cells, constituting
10% of V1 cells, formed two populations, redgreen (L vs M; 66 of 83) and blueyellow (S vs L+M; 17 of 83). Many cone-opponent cells (48 of 83) were double-opponent, with circular receptive-field centers and crescent-shaped surrounds (0.63° offset) that had opposite chromatic tuning to the centers and a time-to-peak 11 ms later than the centers. The remaining cone-opponent cells were either spatially opponent in only one cone system (20 of 83) or lacked spatial opponency (15 of 83). Cells lacking spatial opponency had smaller receptive fields (0.50.7°) than spatial-opponent cell centers (
1°). We found that redgreen cells received S-cone input, which aligned with M input, and, unlike blueyellow cells, redgreen cells gave pushpull responses: receptive-field centers of red-ON cells were excited by both L increments (bright red) and M decrements (dark red) and were suppressed by both L decrements (dark green) and M increments (bright green). Excitatory responses to decrements were slightly larger than to increments, which may account for the lower detection and discrimination thresholds of decrements shown psychophysically. By virtue of their specialized receptive fields, the neurons described here spatially transform the cone signals and represent the first stage in the visual system at which spatially opponent color calculations are made.
Key words: receptive-field; primate; V1; color; double-opponent; color constancy
Correspondence should be addressed to Bevil R. Conway, Department of Neurobiology, Harvard Medical School, Boston, MA 02115. Email: bconway{at}hms.harvard.edu
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eLetters:
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- Do double opponent color cells solve the problem of color constancy?
- Tony Vladusich
- J. Neurosci. Online, 4 Jan 2007
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