Synaptically coupled local networks of neurons process and transform sensory inputs and inputs from higher processing levels. These interactions are thought to contribute to adaptive sensorimotor behaviors by responding dynamically to changes in the external environment, and to changes in the brain's internal representation of this environment. In previous studies the applicants used single unit recordings, computer modeling and dynamical system analysis to describe how the interplay between intrinsic membrane properties and local circuit interactions affect processing of thalamic inputs by intracortical circuits in the rat barrel (somatosensory) cortex. They now propose to apply these tools to study the thalamic circuitry itself. This circuitry involves reciprocal interactions between inhibitory neurons in the reticular nucleus of the thalamus (RT) and thalamocortical (TC) neurons. RT neurons receive both TC and corticothalamic inputs, and possess striking non-linear properties. These properties, and interactions among themselves and with TC cells, strategically position RT neurons both for gating and for modulating the transmission of sensory information to the cortex. The proposed experiments will employ single-unit extracellular recordings in conjunction with controlled whisker stimuli or whisker-based behavioral paradigms. Mathematical analyses will be used to characterize the dynamics of the individual neurons and of the circuits in which the are embedded. An understanding of the role of local circuits in generating dynamic properties of distributed neuronal systems in essential for bridging the gap between cellular physiology and eventual diagnosis and treatment of perceptual/motor and other cognitive dysfunctions associated with trauma and disease states of the central nervous system.
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