From measurements in the monkey visual cortex, we know that neurons in certain visual areas respond well to colored stimuli, while neurons in other areas respond well to moving stimuli. Lesions of certain visual areas are devastating to visual function, while lesions of other areas result in modest visual deficits, as if their function can be taken over by the remaining parts of the brain. A central theme in modern visual neuroscience is to understand the organization and function of these visual areas. Methods Our group has undertaken several studies in which we successfully located distinct regions within the human brain. Subjects view a computer-generated image projected onto a rear-projection screen placed within the magnet. The image consists of flickering spots that move about the visual field in a systematic way. As the spots move, they cause position of neural activity in the several visual areas to shift systematically. Using the ~RI signal, we can track the changing spatial pattern of activity as the stimulus moves anduse the changing spatial pattern of brain activity to locate different cortical area positions. We have developed methods of integrating the measurements from several different images into a single picture. The cortical gray matter in the collection of images forms a curved surface in the brain, and we have unfolded the gray matter, by computational means, into a single image. The algorithms to perform this unfolding are quite new and a recent advance. Results and Discussion We succeeded at localizing different visual areas and have begun the task of measuring how these areas are used to perceive spatial position in the visual field, the color objects, and where different visual cues are integrated to form judgments of boundaries and shape. The facilities of the Lucas Center provide us with an exciting new tool that permit us to explore the organization and structure of neural activity in the human braln.
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