Functional Microcircuits of Sensory Neocortex

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The cerebral neocortex plays a crucial role in perception, action and higher cognitive processes and this has led to an intense effort to understand the functional properties ofthis tissue. Major goals of this effort have been to elucidate the mechanisms whereby individual cortical neurons obtain their diverse response properties and how ensemblesof cortical neurons interact to produce global perceptual and behavioral capabilities. The proposed research, conducted in the rabbit, is aimed at understanding themechanisms governing cortical function in the awake, intact, thalamocortical somatosensory system. The work is aimed at understanding the transformations performed upon thalamocortical inputs to the cortex by the intracortical circuitry, the role of feed-forward inhibitory interneuronsin producing these transformations, and how these transformations lead to parallel and distinct efferent outflows. Using novel multi-electrode methodology, the activity of thalamocortical projection neurons, cortical output (projection neurons), and putative inhibitory interneurons will be simultaneously recorded, and interactions among these identified elements will be analyzed using methods of cross-correlation and microstimulation. Paired intracortical recordings (intracellular/extracellular) will also yield information about interactions between interneurons and their neighboring intracortical targets. Special emphasis will be placed on understanding: (a) the rules governing the specificity of functional connections among the populations of thalamocortical and cortical neurons under study, and (b) the mechanisms underlying feed-forward intracorticalinhibition. The data obtained from these experiments will offer a unique view of the physiology of individual cortical neurons studied under natural conditions, and will provide insight into interactive networks of cortical neurons and their varied functional properties. Such information isessential if we are to understand how neocortical networks generates perception, action, and higher cognitive processes.