Chromatic micromaps in primary visual cortex

Soumya Chatterjee,Kenichi Ohki,R Clay Reid

doi:10.1038/s41467-021-22488-3

Abstract

The clustering of neurons with similar response properties is a conspicuous feature of neocortex. In primary visual cortex (V1), maps of several properties like orientation preference are well described, but the functional architecture of color, central to visual perception in trichromatic primates, is not. Here we used two-photon calcium imaging in macaques to examine the fine structure of chromatic representation and found that neurons responsive to spatially uniform, chromatic stimuli form unambiguous clusters that coincide with blobs. Further, these responsive groups have marked substructure, segregating into smaller ensembles or micromaps with distinct chromatic signatures that appear columnar in upper layer 2/3. Spatially structured chromatic stimuli revealed maps built on the same micromap framework but with larger subdomains that go well beyond blobs. We conclude that V1 has an architecture for color representation that switches between blobs and a combined blob/interblob system based on the spatial content of the visual scene.

Highlights

The clustering of neurons with similar response properties is a conspicuous feature of neocortex
We found that full micromaps extended to form columns in upper layer 2/3, as shown by collapsing the data collected from five different depths into a single map (Fig. 2g; see Supplementary Fig. 3a–e for individual depths)
Vector-based classification of color tuning, we found that this unbalanced gain between the two color axes caused a redistribution of cells classified as blue/yellow to red/green, away from the yellow (–S) class, which saw the smallest increase in response to structured stimuli

Summary

Introduction

The clustering of neurons with similar response properties is a conspicuous feature of neocortex. We used two-photon calcium imaging in macaques to examine the fine structure of chromatic representation and found that neurons responsive to spatially uniform, chromatic stimuli form unambiguous clusters that coincide with blobs. These responsive groups have marked substructure, segregating into smaller ensembles or micromaps with distinct chromatic signatures that appear columnar in upper layer 2/3. We examined the fine-scale arrangement of these chromatic patches in macaque V1 with single-cell resolution using two-photon calcium imaging[16,17]

Methods

Results

Conclusion