Multimodal sensory modulation and human motor control

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In order to interact in our environment during everyday activities, the central nervous system (CNS) must identify and extract relevant sensory information from a vast array of concurrent inputs from multiple sensory modalities.  Such processing is essential for accurately controlling movements, learning novel motor skills and successfully relearning movement patterns following brain injury.  Sensory inputs initially arrive and are processed at very distinct, modality specific areas of the cortex before being integrated in sensory association cortices. Previous research has provided detailed characterization and mechanistic information regarding how sensory inputs within a specific modality are represented during movement at a relatively early cortical level.  For example, our ongoing research suggests that selection of somatosensory information begins to occur at the very earliest stage of cortical processing, the primary somatosensory cortex, during sensory-guided movement and perceptual discrimination.  Highly selective mechanisms appear to be involved, including inhibition of ascending cortical paths carrying task-irrelevant information and facilitation of those carrying task-relevant information.  The specific regions that control this selection are unclear, however interactions between the prefrontal cortex, thalamus, multimodal sensory regions and primary unimodal sensory cortices appear to play an important role.  However, much less is known about how these mechanisms of control are altered when the central nervous system is presented with multiple sources of sensory inputs, as is usually the case during natural movement.  Our current work suggests that the cortical representations of competitive visual and tactile input change substantially depending on the task-relevance of the stimuli and on the spatial and temporal relationship between visual and somatosensory information.  As such the proposed research program will focus on developing fundamental understanding of the interactions and integration of sensory inputs from multiple modalities at a cortical level and the role this plays in the acquisition and control of normal limb movement.