DEVELOPMENT OF FORM, RIVALRY AND BINOCULARITY

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DESCRIPTION (Adapted from applicant's abstract): When very different images are presented to the two eyes, they are not seen simultaneously, rather they alternate in perceptual dominance, a phenomenon known as rivalry. Rivalry is often considered to be the result of competitive interactions between separate monocular representations located at an early stage of visual processing. This view has been challenged recently by new neurophysiological data indicating that modulation of cell responses by rivalrous stimuli occurs exclusively in binocular cells - particularly those outside of early visual areas. New psychophysical demonstrations and rediscovery of several old ones are also incompatible with older views and suggest that rivalry is a higher-order process occurring after the site of binocular convergence. We have developed an objective electrophysiological measure of rivalry that correlates well with subjective reports of rivalry in adults. The technique differs from previous ones in that rivalry can be detected solely on the basis of brain electrical activity. We have applied this technique in normally developing infants between 5 and 15 months of age and have failed to find any evidence of rivalry alternation. Control experiments with non-rivalrous stimuli indicate that the infants have binocular interactions under the spatio-temporal conditions used to test rivalry. The purpose of this project is to examine this apparent disassociation within a developmental context using a new electrophysiological approach. If rivalry and elementary binocular interactions have distinctly different developmental sequences, as suggested by preliminary data, support will be give to the new view of rivalry as a higher-order perceptual phenomenon. If on the other hand, tight linkage is seen between the development of binocular mechanisms and rivalry, support will be given to the traditional view. The proposed experiments are agnostic regarding the new or traditional views and are designed to be useful, regardless of their outcome. Moreover, a substantial amount of otherwise interesting data on orientation-domain interactions and binocularity will also be obtained that will be helpful for understanding the normal developmental sequences of both binocular vision and form vision, independent of their relationship to the development of rivalry.