The primate visual system analyzes incoming visual information according to a sparse set of fundamental features. Feature-selective neurons provide a detailed analysis of the local features in visual scenes, such as information about stimulus orientation, motion direction, and so forth. The neural representation of visual features has been studied extensively in non-human primates but has proven challenging to study in humans due to the limited spatial resolution of noninvasive neuroimaging methods. My lab has developed novel analysis techniques to measure the feature tuning properties of the human visual system using functional magnetic resonance imaging (fMRI). Our preliminary studies show that different stimulus orientations and motion directions evoke distinct patterns of ensemble fMRI activity in the human visual cortex that can be reliably classified by statistical algorithms. This project will apply this novel pattern analysis approach to investigate the neural representations of orientation and motion direction in the human cortex and the role of visual attention in feature perception. The proposed studies will evaluate whether activity in early human visual areas corresponds with visual feature perception across changes in the surface properties of the stimulus.
Specific Aim 1 will investigate the orientation-selective properties of early visual areas, and determine whether these areas show evidence of cue-invariant orientation selectivity that can effectively generalize across changes in stimulus form.
Specific Aim 2 will assess direction selectivity in visual areas V1 through V4 and MT+, and test for cue-invariant direction selectivity and sensitivity to perceived global motion.
Specific Aim 3 will explore the role of visual attention in selecting and stabilizing the representations of visual features. The results from this project will provide important new insights into the human neural bases of visual feature perception, and help provide a bridge between animal and human studies. The ability to measure the feature-selective properties of an individual's brain may also have high clinical significance. This approach may lead to effective new tools to investigate, characterize, or diagnose impairments in cortical visual function resulting from disease or injury, or methods to evaluate the cortical effects of medical treatment or recovery of function.
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