Oscillatory network dynamics provide an intermediate phenotype that, in some human imaging studies, has proven to be a more fruitful correlation target than behavioral measures for identifying genetic biomarkers of psychiatric disorders. Using rodent models, we propose to study oscillatory long-range synchronization and its alterations in schizophrenia, as well as disturbances in developmental trajectories of oscillatory networks from adolescence to adulthood. The primary focus is the impaired rhythmic coordination between activities in the hippocampus (HC) and prefrontal cortex (PFC) which is particularly important for specific cognitive functions in the adult and was also shown to play an important role in early neurodevelopment. Abnormal functional connectivity between HC and PFC has been demonstrated in schizophrenic patients and in chronic animal models of schizophrenia. Since pathological alterations of the key elements of neuronal oscillatory networks are present in both HC and PFC, impaired cortico-hippocampal synchronization can originate from the pathology of either or both structures. We propose to examine this issue using a novel approach that can precisely define the spatial distribution of rhythmic generators and quantify their interactions, including the essential directional influences. We will systematically investigate the spectral structure, the anatomy, physiology, and pharmacology of these interactions in normal rats and in pharmacological models of schizophrenia. We further hypothesize that impaired oscillations also adversely affect the maturation of cortical networks and their long-range connections. Understanding the ontogeny of temporal dynamics and their control is a severe gap area in the field, because oscillations are critical for normal cognition ad seem to be impaired not just in schizophrenia, but also in autism, and other mental illnesses. Thus we will also investigate the normal development of HC-PFC relationship through adolescence and early adulthood and its pathological alterations in a neurodevelopmental model of schizophrenia using daily electrophysiological recordings; such a longitudinal design has not been attempted in prior studies.
Specific Aim 1 is to establish the pattern of PFC- HC interactions including directional information. We propose that long-range influences synchronizing neuronal activity and gamma oscillations between HC and PFC are active in both directions, with an overall HC dominance. We will investigate the anatomical substrate of these bidirectional interactions and their role in a cognitive task which requires dynamic PFC-HC coupling.
Specific Aim 2 is to examine the impaired PFC-HC interactions in pharmacological models of schizophrenia using NMDA receptor antagonists and dopamine D4 receptor agonists which, besides schizophrenia-relevant symptoms, are known to significantly alter brain oscillations and to reduce performance on cognitive tasks requiring functional PFC and HC networks.
Specific Aim 3 is to define how oscillation networks develop through the periadolescent period in normal rats and in a neurodevelopmental model of schizophrenia. We propose a longitudinal study to investigate how the adult pattern of oscillatory synchronization develops and when and how the developmental trajectories in the schizophrenia model diverge from normal.
Treatment-resistant cognitive impairment of schizophrenics is a major public health issue. Using recently developed innovative analysis techniques, this study will investigate the mechanism of how schizophrenia- relevant structural abnormalities in the cortical microcircuitry lead to deficits in long-range communication between different cortical and hippocampal regions. This research will also determine how this will affect cognition and neurodevelopment during adolescence and early adulthood.
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