Neural mechanisms of color in extrastriate cortex

Wellesley College, Wellesley Hills MA

Investigators

Abstract

How does the brain determine the colors we see? The retina contains three cone types, but each cone is actually colorblind: the red-sensitive cone cannot tell the difference between a dim yellow-green and a bright blue. Theoretically color can be calculated by comparing the activity of the different cone types, but how the brain does this remains mysterious. This project will investigate how cone signals are processed by specialized brain regions thought to be important in color perception. It will employ functional magnetic resonance imaging (fMRI) to generate an overview of regions involved in color in the macaque monkey, a model of human trichromatic color vision. Microelectrodes will then be targeted to specific regions identified by fMRI. By correlating the patterns of neural activity of single neurons with controlled visual stimuli, this project will test hypotheses about the function of the neurons in encoding color percepts. One important question that will be addressed is how color-selective neurons sample the cone signals to achieve color selectivity. This project aims to reveal not only the neural mechanisms underlying color, but more generally the principles that govern how neural circuits transform sensory stimuli into perception and behavior. It will provide a unique opportunity to train undergraduate women in the use of cutting-edge systems research technology, and will foster inter-institutional networks and partnerships. The results will have broad impact: they will be useful to engineers interested building artificial vision systems, and will engage the general public by tackling important questions such as how and why color is compelling. Finally, by combining single-unit electrophysiology and fMRI in the same subjects, this project will further our knowledge of the neural basis for fMRI, which is still poorly understood, despite the fact that fMRI is the most widely used clinical tool for assessing brain function.