CROSS-MODAL INTERACTIONS BETWEEN VISION AND TOUCH

DESCRIPTION (provided by applicant): The work proposed here is a continuation of ongoing research aimed at understanding cross-modal interactions between touch and vision. The long-term objective is to expand knowledge of multisensory processing, as well as its interactions with language and the plasticity of the underlying neural mechanisms, with a view to devising novel neuro- rehabilitative approaches in many contexts, including blindness, autism, traumatic brain injury and focal deficits following stroke, brain tumors or epilepsy. In the last grant cycle, we used functional magnetic resonance imaging (fMRI) to reveal segregated processing of haptic object properties: shape, texture and location, with evidence for substantial convergence of visual and haptic processing, and developed a conceptual model of multisensory object representation in visual object-selective cortex. Specific Aim I of the present application proposes to test the functional localization of the processing of haptic object properties using transcranial magnetic stimulation (TMS). In Specific Aim II, we use fMRI to examine the factors that determine segregation of activity within visual cortical activity in the congenitally blind, and explore the relationship between linguistic and perceptual processing as underpinnings of such activity in relation to the theory of grounded cognition. Specific Aim III seeks to build on our recent, exciting finding that listening to sentences containing textural metaphors (e.g. He had a rough day) recruits texture-selective somatosensory cortex while listening to sentencing containing shape metaphors recruits shape-selective visual cortex, by exploring domain-specific recruitment of sensory cortical areas during metaphorical cognition, using fMRI in both sighted and blind individuals. Further, we will use TMS to test whether these activations are functionally meaningful, rather than epiphenomenal. This work, apart from further elucidating interactions between vision and touch, will offer new insights into the relationship between perceptual and linguistic processes in the sighted and the congenitally blind, which is relevant for understanding not only of cross-modal plasticity but also of disorders such as autism and traumatic brain injury, where known deficits in metaphor comprehension may reflect defective integrative processing of the kind studied here.