Normal vision begins and ends with a rapid, saccadic eye movement. While much is known about the final stages of saccade generation in the brainstem as well as about the first steps of visual processing, there is no information about how the target for a saccade is selected. Thus, the long-term objective of the proposed work is to understand how pattern recognition by the visual system and cognitive processing direct gaze. The purpose of these experiments is to investigate the respective roles in saccade target selection of two specific areas of cerebral cortex in rhesus monkey (Macaca mulatta): the frontal and supplementary eye fields, which are at the interface of visual processing and motor output. While in previous neurophysiological studies of these areas, saccades were directed by a single target, the proposed experiments are designed to study the neural activation associated with saccades generated in response to more complex stimulus arrays. Single neurons will be recorded while monkeys generate saccades to perform a variety of visual detection, search and matching tasks. The analysis of the data will aim to distinguish neurons with activity not solely dictated by the arrangement of the stimuli or the execution of the saccade but instead reflecting the processing required to discriminate the target from the distractors. Neuronal activity will also be recorded while monkeys generate saccades to stimuli presented during binocular rivalry in an effort to understand the factors involved in bringing the target to conscious awareness. The strength of this proposal lies in the simultaneous assessment of visuomotor behavior and the activity of neurons which are candidates for generating key elements of the observed behavior. Successful completion of these experiments will provide new knowledge about the neural mechanisms in frontal cortex responsible for selecting the target for a saccade and generating visually-guided eye movements. This information is necessary for understanding the nature of the gaze control problems associated with frontal lobe dysfunction consequent to a number of diseases.
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