Visual motion perception plays a critical role in the control of action, and has been studied extensively using both human behavior (psychophysics) and animal physiology (single-neuron recordings). However, theories of how the human brain processes visual motion have not been tested directly-- by measurement of human brain activity. In this talk, I’ll describe experiments that use functional magnetic resonance imaging (fMRI) to identify and characterize motion-specific human brain activity, and to relate this activity to human percepts of motion.
First, I’ll address the relationship between neural activity and the perception of a well-known motion illusion, the motion aftereffect. Second, I’ll describe experiments designed to identify neurons in the human brain that represent the direction of visual motion, and to quantify the relative degrees of direction-selectivity across the many human cortical areas involved in vision. Third, I will test a theory of how the brain combines motion information in order to represent the direction of moving objects independent of their particular spatial pattern.
Together, these findings provide quantitative information about neural response properties, cortical organization, and the transformations of information performed by motion-responsive neurons in the human brain. I’ll conclude by suggesting that this quantitative, physiological approach can be extended beyond the study of sensory processing to begin investigating the neural basis of human decision-making.