Coding of chromatic spatial contrast by macaque V1 neurons

Abstract

Color perception relies on spatial comparisons of chromatic signals, but how the brain performs these comparisons is poorly understood. Here, we show that many V1 neurons compare signals across their receptive fields (RF) using a common principle. We estimated the spatial-chromatic RFs of each neuron, and then measured neural selectivity to customized colored edges that were sampled using a novel closed-loop technique. We found that many double-opponent (DO) cells, which have spatially and chromatically opponent RFs, responded to chromatic contrast as a weighted sum, akin to how simple cells respond to luminance contrast. Other neurons integrated chromatic signals non-linearly, confirming that linear signal integration is not an obligate property of V1 neurons. The functional similarity of DO and simple cells suggests a common underlying neural circuitry, promotes the construction of image-computable models for full-color image representation, and sheds new light on V1 complex cells.

Temporal filtering of luminance and chromaticity in macaque visual cortex

“…Monkeys have luminancetuned simple cells, like cats do, but unlike cats, monkeys have a large population of cone-opponent V1 neurons. Some of these cone-opponent neurons combine visual signals antagonistically and roughly linearly across their RFs, consistent with the push-pull model (Conway and Livingstone, 2006;De and Horwitz, 2021). One possibility that is consistent with the results of this study is that push-pull excitation-inhibition reduces the SNR of high-frequency cone-opponent and non-opponent modulations similarly in V1.…”