The contribution of human color vision to second order motion processing

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Most people are aware that different parts of the brain are specialized for sensory different tasks, such as vision, hearing, touch and smell. What is less often appreciated is that, even within one sense such as vision, different areas of the cortex are specialized for the processing of different visual attributes. This proposal investigates the specialization of the visual cortex for the attributes of color and motion in the human brain. A true cortical segregation of color and motion processing would suggest that our color vision could not be used to see movement in the image. For over 25 years it has been controversial whether color vision does actually fail at the processing of motion, or whether its deficiency for motion perception is relatively mild and insignificant. I propose to use a combination of approaches, direct measurement of human visual capabilities in combination with the latest fMRI brain imaging techniques, to resolve this issue. In the proposal I design new visual stimuli to investigate the responses of the human brain areas to motion, especially area MT, which is thought to be specialized for motion perception. My experiments aim to reveal the different components of the motion signal that are integrated by this brain area to yield the overall movement of complex stimuli. In particular I will investigate the extent to which motion motion perception is based on linear versus nonlinear local motion components in both colour and achromatic vision. The fMRI experiments aim to image directly in a brain scanner the areas of the human brain activated by moving chromatic and achromatic stimuli. I will compare brain activity for stimuli moving coherently in a unified direction as compared to incoherently in random directions, and compare activities for moving stimuli based on linear versus nonlinear local components. This linkage of behavioural and imaging techniques is a crucial step in understanding the physiological basis of colour and motion perception.