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Jonathan W Peirce, Samuel G Solomon, Jason Forte, John Krauskopf, Peter Lennie; Chromatic tuning of binocular neurons in early visual cortex. Journal of Vision 2003;3(9):24. doi: 10.1167/3.9.24.
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© ARVO (1962-2015); The Authors (2016-present)
Most simple and complex cells in V1 and V2 are binocularly driven. The spatial characteristics of the two eyes' receptive fields are generally very similar. We wanted to know whether neurons strongly responsive to isoluminant stimuli were also binocularly driven and, if so, how well matched were the chromatic properties of the receptive fields.
We recorded from single units in V1 and V2 of macaques prepared for acute physiological experiments. For each cell we characterized the spatial properties of the two receptive fields using drifting sinusoidal gratings. With gratings of optimal spatial configuration we then measured responsivity to chromatic modulation along a range of directions in color space. The preferred color direction was calculated for each cell, with confidence intervals determined by consistency of the responses across trials.
We found that many binocularly driven cells responded well to isoluminant gratings. Furthermore, among cells that preferred isoluminant modulation the optimal color directions in the two eyes never differed significantly. This similarity of chromatic tuning in the two receptive fields is unlikely to have arisen by chance, suggesting that it is important for the cells' function. Binocularly driven cells that respond well to isoluminant modulation are a potential substrate for chromatic stereopsis. However, most of these cells exhibited low-pass spatial frequency tuning, and therefore lack the receptive field structure most commonly associated with disparity sensitivity. Their role in stereopsis remains in doubt.
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