Intrinsic and evoked oscillatory brain activity as potential endophenotypes for schizophrenia and psychotic disorders
Ethridge, Lauren Elizabeth
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Evidence for a genetic component for schizophrenia has led to a search for potential endophenotypes that will aid in identifying genetic risk for schizophrenia as well as increase understanding of the etiology of the disorder. Endophenotypes by definition must be unique to the disorder of interest, so it is necessary to discriminate neural processing abnormalities between psychiatric groups. Utilizing electroencephalography (EEG) to measure time-frequency characteristics of the neural response to a steady-state stimulus and two modalities of oddball stimuli, the present work contributes a number of important advances to the current literature on the use of intrinsic and evoked neural activity to develop endophenotypes for schizophrenia, psychotic bipolar disorder (BPP), and general psychosis. Abnormalities in prestimulus intrinsic activity are characteristic of schizophrenia and these abnormalities may interact with subsequent task-related processing, producing commonly observed deficits in steady-state and event-related potential (ERP) responses. Commonly observed deficits in oscillatory response to the auditory oddball task are not unique to schizophrenia, but may be indicative of risk for psychosis in general. However, the late beta/gamma accentuation to auditory oddball stimuli discriminates schizophrenia, BPP, and healthy subjects, being unique to BPP. Late beta single trial power to both targets and standards is also heritable in healthy twins, suggesting that this variable may provide an interesting avenue for further examination as an endophenotype for BPP.