BINOCULAR INTERACTION IN HUMAN VISUAL CORTEX

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Early detection and correction of binocular visual disorders are crucial for the proper maturation of the young visual system during the sensitive period of development. A technique for assessment of binocular interaction in the human visual cortex known as the Binocular Beat Technique (BBT) has shown great promise for use as a marker for cortical binocular integration. This involves the dichoptic presentation of uniform fields which are sinusoidally modulated in luminance with differing temporal frequencies between the eyes. It evokes a unique response termed the "binocular beat" which is a visual evoked potential (VEP) component reflecting nonlinear neural behavior and which could only arise from integrative binocular units. This beat can also be observed perceptually in normal adults. Individuals with strabismus or amblyopia, which accompany disrupted binocular function in the visual cortex manifest severe reductions in this nonlinearity, suggesting an abnormality in the binocular cortical processes underlying this response Because this uniform-field stimulus doe snot require accurate accommodation, fixation, vergence or high spatial resolution, this technique has significant potential as a tool for assessment of infant binocularity. In this proposal, the following problems of neurophysiological and clinical interest will be addressed: 1) the clinical usefulness of the beat as an indicant of binocular function, 2) the developmental course of the binocular beat in infants, 3) intrasubject comparison between the VEP beat response and VEP elicited by random-dot stereograms as an indicant of cortical binocularity, 4) the differential effects of sleep/awake states on the VEP beat responses, 5) spatiotemporal aspects of the binocular beat, 6) cortical topology of the mechanisms generating the beat nonlinearity and 7) application of other nonlinear systems analysis approaches (including white-noise stimulation) for exploring the nature of the nonlinear mechanism(s) producing the binocular beat.