Sensitivity to motion and binocular cues are both of vital adaptive significance. While single unit studies have provided detailed information on the spatio-temporal dynamics of direction-selectivity and binocularity in individual cortical areas and human fMRI studies have mapped slow hemodynamic responses in multiple human visual areas, neither approach provides an analysis of the functional dynamics of these networks. We have developed EEG-based source-imaging and signal analysis tools that we will use to develop predictive dynamical models of motion processing and binocular interaction throughout cortex at a spatial resolution that is on the order of 2 cm or less.
In Aim 1 we will use EEG-source imaging and perceptual measurements to compare the functional form of spatio-temporal interactions underlying long- versus short-range apparent motion and to map their sites of generation. Direction-specific adaptation will be used to confirm which response components are due to motion mechanisms. We will also vary the observer's task in order to determine the extent of top-down (feedback) influences on apparent motion processing. A bistable apparent motion stimulus will be used to compare responses during episodes when apparent motion is perceived to when it is not.
In Aim 2 we will apply recent technical developments in EEG source-imaging to the study of motion responses in the extra-striate cortex of typically developing humans infants between two and six months of age. These data will be used to test models of motion processing and to identify periods of rapid development.
In Aim 3 we will study the relationship between intact motion processing and functional binocular interaction in patients with strabismus/amblyopia. Across the three Aims, four independent criteria (cortical locus, developmental dissociation, dependence on attention and pattern of non-linear interaction) will be used to provide converging evidence regarding the existence of multiple motion processing sub-systems as predicted by psychophysicists.
The methods of dynamic functional imaging that will be developed in this proposal will provide a powerful new approach for understanding normal and abnormal visual processing throughout development. Because these methods are applicable in human, they provide an important translational bridge between direct neural measurements that can only be done in experimental animals and functional studies of the intact human brain, including studies of patients undergoing treatment
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