Critical period in visual cortex: inhibitory circuits

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DESCRIPTION (provided by applicant): A central issue in neuroscience is to understand how experience shapes brain function. Recent studies in visual cortex suggest that the maturation of intracortical inhibitory circuits is necessary to initiate and drive ocular dominance plasticity during the critical period. However, the maturation and regulation of the specific type of inhibitory circuit involved is not understood. Critical period plasticity is also modulated by visual deprivation and BDNF over-expression, although the cellular mechanisms remain unknown. Here we hypothesize that the functional maturation of a specific subtype of GABAergic neurons, parvalbumin (Pv) basket interneurons, are a component of the inhibitory mechanism underlying critical period plasticity, and a cellular target of experience deprivation and BDNF regulation. Using bacterial artificial chromosome transgenic (BAC) mice expressing GFP in Pv-interneurons, we will characterize the morphological and physiological development of Pv-interneurons using two photon laser scanning microscopy and electrophysiology in brain slices. We will then examine the effects of dark rearing on the maturation of Pv-interneurons. Finally, we will test the role of BDNF in experience-dependent maturation of Pv-interneurons by blocking trkB signaling using BAC transgenic mice expressing a dominant negative form of trkB receptor specifically in Pv-intemeurons. These results will reveal a mechanism by which experience shapes function of an identified inhibitory network and provide strong evidence that maturation of the Pv-interneuron circuit facilitates the coding of visual information necessary to drive ocular dominance plasticity. The knowledge gained will aid in the design of drug treatments in diseased states such as epilepsy and schizophrenia.