Nonlinear Thalamocortical Transformations

Harvard University, Cambridge MA

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Abstract

DESCRIPTION (provided by applicant): The role of the early stages of sensory processing in the brain is to transform signals in the sensory world to provide higher stages of processing with representations that eventually give rise to perception and memory, as well as feedback for motor control. The spatial and temporal transformations by the various stages of processing and the corresponding role of the interplay between sub-populations of excitatory and inhibitory neurons within the pathway in performing these transformations are not well understood. We propose to quantify thalamic and cortical transformations of tactile patterns in the somatosensory pathway through a combination of extracellular recording in the thalamocortical pathway of the rat vibrissa (whisker)system and functional modeling of the corresponding spatial and temporal dynamics, The vibrissa system is an exquisite active sensory modality that rats can use to discriminate between very similarly textured surfaces based on vibrissal exploration alone, an serves as an excellent model system for understanding the transformations of sensory stimuli into thalamic and cortical representations that eventually give rise to perception. The specific aims of this work are to: 1) quantify the transformations induced by the nonlinear temporal dynamics of the thalamus and cortex during the encoding of naturalistic tactile stimuli, 2) quantify nonlinear spatiotemporal transformations in the thalamus and cortex during the encoding of naturalistic tactile stimuli, and 3) determine to what extent these patterns of stimuli can be predicted from known functional properties of the thalamocortical circuit through both biophysically inspired models and estimation techniques focused on nonlinear dynamics. The characterization of these transformations is critical in controlling neuronal function through engineered prosthetic devices in the central nervous system, in order to provide assistance to individuals who have lost sensory function due to disease or trauma, when peripheral devices are not possible or appropriate.