Current evidence suggests that the occipital cortex (normally associated with visual perception) actively participates in non-visual sensory tasks. For example, it has been demonstrated both in sighted and blind individuals that this area is implicated in the processing of sensory information obtained through touch. The purpose of this research proposal is to investigate the neurophysiology and neuroplasticity of cross-modal sensory interactions. Specifically, the study has three aims:
(Aim 1). In congenitally blind and sighted individuals, what roles do occipital (visual) cortical areas play in tactile spatial discrimination tasks? (Aim 2) Does the tactile exploration of complex objects and visual scenes (e.g., faces and houses) by sighted and blind individuals activate known higher-order visual areas? (Aim 3) Does tactile stimulation modulate occipital cortex function? We will employ fMRI and TMS to pursue these questions. Subjects will perform spatial discrimination and object recognition tasks to tactile presented stimuli (simple raised dot texture patterns and complex objects such as faces), fMRI will be used to map and compare the cortical areas activated during these tactile tasks in the sighted and blind. In a second set of experiments, we will assess the modulation of occipital cortex activity and function during a cross-modal visuo-tactile task. TMS will be used to induce and assess changes in phosphene perception as a function of simultaneous tactile stimulation. The candidate wishes to learn, master and combine the techniques of fMRI and TMS with the goal of becoming an independent clinician-scientist. The proposed experiments will contribute to our understanding as to how objects are represented within the visual brain and how information obtained from touch contributes to this processing. Furthermore, comparing these processes in the blind will help uncover the adaptive mechanisms underlying object representation in the absence of vision. These results are likely to have implications for both the rehabilitation and education of the blind and visually impaired.
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