QUANTITATIVE STUDIES OF VISUAL PATHWAYS IN PRIMATE

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The overall aim is to understand how central visual pathways analyze information about the chromatic and spatial properties of objects. Five projects are proposed, all of which are intended to explicate the links between color vision and its underlying physiology. The work involves both physiological experiments and on macaque monkey (recording from Lateral Geniculate Nucleus (LGN), striate cortex an cortical areas V2 and V4) and psychophysical experiments on human, in all of which I shall measure sensitivity to patterns displayed on a color television monitor. The first project will investigate the multiplexing of chromatic signals seen in neurons in parvocellular layers of LGN. Can one see perceptual signs of this double-duty done by neurons, and can the chromatic and achromatic signals be distinguished in the discharge patterns of cells? The second project will examine the action of post-receptoral mechanisms of chromatic adaptation. Are there several of them, are they distinguished by their chromatic or temporal properties, and where in the visual pathway do they lie? The third project will examine the reliability with which neurons in striate and extrastriate cortex can distinguish hues, and will examine mechanism that could produce the sharp tuning for hue seen in some neurons. The fourth project will examine the role of simultaneous contrast (chromatic induction) and will investigate its possible physiological substrates. The final project will examine whether neurons in extrastriate cortex could play a role in color constancy. How do they weigh chromatic signals from different parts of the receptive field, and how is their sensitivity regulated by the accumulated signal?