![]() Previously we have reported that the history of visual hallucination symptoms in chronic schizophrenia patients was positively correlated with the degree of phase locking of a β oscillation recorded over visual cortex. ![]() Since the precise synchronization of neural activity in the γ band (30–100 Hz) of the electroencephalogram (EEG) may underlie the representation of perceptions, γ oscillation abnormalities could be related to hallucinations in schizophrenia. Hallucinations – perceptions without a basis in the physical environment – are a hallmark symptom of schizophrenia. In addition, they provide further support for the hypothesis that hallucinations are related to cortical hyperexcitability, which is manifested by an increased propensity for high-frequency synchronization in modality-specific cortical areas. These findings suggest that differential neural circuit abnormalities may be present in the left and right auditory cortices in schizophrenia. Furthermore, the correlations between source evoked power and PLF found in HC was reduced in SZ for the LH sources. Left hemisphere source PLF in SZ was positively correlated with auditory hallucination symptoms, and was modulated by delta phase. PLF was reduced in SZ for non-homologous right and left hemisphere sources. Phase locking factor (PLF) and evoked power were reduced in SZ at fronto-central electrodes, replicating prior findings. Time-frequency decomposition was performed on the scalp EEG and source data. A 5-dipole model was fit from the HC grand average ASSR, with 2 pairs of superior temporal dipoles and a deep midline dipole. The EEG was recorded from 60 electrodes and average-referenced offline. Sixteen healthy control subjects (HC) and 18 chronic schizophrenia patients (SZ) listened to 40 Hz binaural click trains. ![]() We also examined whether the 40 Hz ASSR deficit in schizophrenia was associated with cross-frequency interactions. Here we tested this hypothesis by examining whether the 40 Hz auditory steady-state response (ASSR) generated in the left primary auditory cortex is positively correlated with auditory hallucination symptoms in schizophrenia. These findings suggest that the propensity for hallucinations is associated with an increased tendency for neural circuits in sensory cortex to enter states of oscillatory synchrony. Previously we have found positive correlations between the phase synchronization of beta and gamma oscillations and hallucination symptoms in schizophrenia patients. Oscillatory electroencephalogram (EEG) abnormalities may reflect neural circuit dysfunction in neuropsychiatric disorders.
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