Advances in color science: from retina to behavior

Abstract

Color has become a premier model system for understanding how information is processed by neural circuits, and for investigating the relationships among genes, neural circuits, and perception. Both the physical stimulus for color and the perceptual output experienced as color are quite well characterized, but the neural mechanisms that underlie the transformation from stimulus to perception are incompletely understood. The past several years have seen important scientific and technical advances that are changing our understanding of these mechanisms. Here, and in the accompanying minisymposium, we review the latest findings and hypotheses regarding color computations in the retina, primary visual cortex, and higher-order visual areas, focusing on non-human primates, a model of human color vision.

Figure 1.

First stages of color. A, Spectral sensitivity functions of the three cone types in trichromatic primates (adapted with permission from Stockman and Brainard, 2010). B, False-colored representation of the cone mosaic of a macaque monkey (scale bar, 0.2°); adapted from Roorda et al. (2001). C, Rainbow showing monochromatic yellow (left) and additive color mixing of lights showing mixed yellow (right).

Figure 2.

Spatial color contrast changes color appearance. The patches indicated by the asterisk are all physically identical. Image courtesy of Beau Lotto (University College London, London, UK).

Figure 3.

Diagrams of various model receptive fields. Top view (left), side view (right). See sections “L–M opponent cell types and circuitry” and “How are the cone cells transformed by V1?” for details.

Figure 4.

Squirrel monkey performing a trichromatic color discrimination following gene therapy. Image courtesy of the Neitz laboratory.

Figure 5.

Alternative models for the organization of color-tuned neurons in V1. The gray patches depict cytochrome-oxidase blobs. Dots show color-tuned neurons that are clustered in blobs, but mixed randomly within each blob (A); clustered in blobs, and segregated according to color tuning within pure-color blobs (B); randomly arranged with respect to blobs (C); and clustered within blobs and according to a micromap in which cells of similar tuning are adjacent within a given blob (D).

Figure 6.

Simple hierarchical model of color processing in the macaque cerebral cortex. Regions of cortex shown in gray, which increase in scale along the visual-processing hierarchy from V1 to TE, are implicated in color processing. Adapted from Conway (2009).