CORTICAL REPRESENTATION OF THE VISUAL IMAGE

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Our objective in this research is to uncover what role cortical neurons play in processing temporal components in a natural visual environment. We will study for V1 neurons and for pursuit eye movements how context modulates the temporal responsiveness, because temporal changes are inherent in normal vision, and visual perception of targets in the natural visual environment is always in context . 1. We will characterize the temporal properties of different classes of V1 neuron for stimulus patterns defined by flicker, motion, color or texture and ask what factors modulate the temporal tuning functions. Neurons will be classified by laminar location and grouped into functional classes. We will study the effect of luminance and color contrast on temporal tuning curves to examine the effects of stimulus contrast on contrast gain. We will compare the effects on temporal response functions of local, overlapping adaptive stimuli with remote, contextual stimuli. In separate experiments we will determine the spatio-temporal response functions of different classes of V1 neurons with stimulus patterns defined by luminance or amplitude modulated texture. 2. We aim to measure the spatio-temporal tuning of visual pursuit by accurate measurement of eye movements in human subjects. We will measure pursuit performance while presenting pursuit targets on textured backgrounds or surrounded by textured contextual stimuli. In this way we can compare the effects of adapting contrast and remote context on V1 neurons and oculomotor performance. Finally, we will study the sensitivity of pursuit eye movements to perturbations in speed, stimulus class or contrast to determine the degree of cue invariance for pursuit. This work will test fundamentally new views of primary visual cortex as an image processing area by determining to what extent elaborate V1 image processing has an effect on behavioral outcome. The significance of this work is its contribution to understanding the relation between cortical information processing and sensorimotor integration.