Functional outcome in individuals with schizophrenia and related disorders is primarily determined by the degree of impairment in certain core cognitive abilities. For example, subjects with schizophrenia exhibit deficits in visual working memory and attention, and altered patterns of cortical activity during tasks that tap these abilities. These patterns of activity depend on the proper temporal firing of neurons distributed across a network that includes primary visual (VI), posterior parietal (PPC) and dorsolateral prefrontal DLPFC) cortices. These findings highlight an unanswered critical question: What are the cortical cellular, circuitry and connectivity bases for the impairments in visual working memory and attention in schizophrenia? To answer this question, the complementary studies in the proposed Center are designed to test the following Central Hypothesis: Intrinsic molecular disturbances in layer 3 pyramidal cells of the neocortex give rise to morphological abnormalities in these neurons. The severity of this cellular pathology is moderated across cortical regions as a function of normal regional differences in the properties of layer 3 pyramidal cells. This cellulr pathology alters cortical circuitry within and between regions, impairs functional connectivity across regions, and results in disturbances in both bottom up and top down processes during visual working memory and attention in individuals with schizophrenia. The five inter-related projects (P) of the proposed Center provide convergent tests of this hypothesis at the molecular, cellular, laminar and local circuitry levels in postmortem human brain (P1&P2), and at the regional and distributed circuitry levels through imaging and neurophysiological studies in never-medicated subjects with a first-episode of psychosis (P5);these studies are both informed and constrained by parallel studies in monkeys (P3&P4). A key innovation of this approach is the integration of studies with multiple levels of resolution, from molecules to behavior, that provide a translational assessment of both bottom up and top down explanations of cortical dysfunction in schizophrenia.
The proposed studies have high clinical relevance as the combination of molecular-cellular-circuit level analyses with in vivo indices of brain function offers a platform for subsequent identification of novel, pathologically-based targets for therapeutic interventions that are accompanied by pathophysiologically informed biomarkers that can be used to predict and monitor the efficacy of such interventions.
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