RUI: Color processing in inferior temporal cortex of macaque monkey

Wellesley College, Wellesley Hills MA

Investigators

Abstract

How does the brain process sensory signals to generate perception and knowledge? This project advances color as a premier system with which to tackle this fundamental question. Contrary to popular opinion, the experience of color is not directly predicted by physical properties of stimuli, exposing the important role that the nervous system plays in transforming information received by the eye into behavior. It is thought that color, like other aspects of vision, is computed by a series of brain structures. But the location of these structures and the computations they perform to bring about color are not known. The proposed work exploits advances in functional brain imaging (fMRI) to identify regions involved in the highest levels of color processing, and will determine how these regions are connected to each other and the rest of the visual pathway. Under carefully controlled experimental conditions, the research will determine which brain regions are necessary for which color tasks using fMRI-guided transient pharmacological blockade. The results are predicted to show that blockade of color-processing regions lower in the visual-processing hierarchy will impair less sophisticated color behaviors such as color discrimination, while blockade of higher-order brain regions will impair more cognitively demanding behaviors such as color categorization. The research environment represents a unique collaboration between a liberal arts women?s college and a major research institution, and will provide exceptional opportunities to train the next generation of female scientists in the most advanced neuroscientific techniques. The results of the work will be widely disseminated through peer-reviewed publications, presentations at national and international conferences, and popular media such as the World Science Festival, providing a mechanism to enhance general literacy in science and technology research. In addition, the techniques, questions and results will be incorporated into undergraduate curricula at Wellesley College and freely available on course websites. (http://academics.wellesley.edu/Neuroscience/Neuro320/) Much is known about how color signals are encoded by the retina and transmitted to the cerebral cortex, but surprisingly little is known about the mechanisms that decode these signals to bring about perceived colors. Extensive preliminary work suggests that color responses are localized within inferior temporal cortex, a large area of the brain known to be involved in the perception and recognition of objects. The proposed experiments test the hypothesis that the color-biased regions of inferior-temporal cortex comprise an interconnected hierarchical network that is necessary for color perception. Specifically, the work will examine the extent to which posterior color-biased regions decode color appearance (hue, saturation) and anterior regions compute more cognitive phenomena such as our ability to carve the continuous hue space into discrete categories. The hypothesis will be tested using a combination of functional magnetic resonance imaging, psychophysics, fMRI-guided pharmacological inactivation, and fMRI-guided tracer injections. The work will answer two fundamental questions: 1. To what extent are different color-biased regions necessary for color-discrimination and color-categorization behavior? 2. Are the color-biased regions connected, and if so, does the pattern of connectivity reflect the predicted hierarchy from posterior to anterior along the temporal pole? Addressing these questions will not only advance our understanding of color processing, but will uncover general principles that underlie how the cerebral cortex processes information. This new knowledge will promote the development of more biologically plausible machine vision systems. The work will yield broad impacts both from scientific discoveries and from complementary activities such as the mentorship of undergraduate women and underrepresented minorities engaged in STEM research; expansion of cross-institutional partnerships; development and dissemination of undergraduate neuroscience course materials; enhancement of public scientific literacy; and strengthening of connections between arts and sciences.