Vision is an active process. We do not see the world directly; rather, we construct a representation of it from sensory inputs in combination with internal, non-visual signals. In the case of spatial perception, our representation of the visual scene takes into account our own movements. This allows us to perceive the world as stationary despite the constant eye movements that produce new images on the retina. How is this perceptual stability achieved? Our central hypothesis is that a corollary discharge of the eye movement command updates, or remaps, an internal representation when the eyes move. We have previously shown that single neurons in the lateral intraparietal area (LIP) and extrastriate visual cortex are activated by the remapped trace of a visual stimulus. These neurons fire in the single-step task, in which a saccade brings the receptive field onto a previously stimulated location. Remapping is also observed in the double-step task, in which the animal makes sequential saccades to two target locations. Our long-term goal is to discover the neural mechanisms that produce remapping. To achieve this we need to learn much more about the phenomenon and about the neural circuitry that supports it. The proposed experiments are designed to discover whether LIP neurons have equal access to visual information from the entire visual field; to determine whether remapping varies with hemifield or distance; to discover the source of remapped visual signals; and to determine the source of the corollary discharge signals used in remapping.
The aim of the proposed work is to elucidate the neural circuitry that contributes to active vision.
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