Correlation between P300 and EEG rhythm in schizophrenia.

We hypothesized that cognitive deficits reflected by P300 abnormality and distorted EEG rhythm in schizophrenia, which might share the subcortical generation system, could be closely associated with each other. Our goal is to assess the relationship between P300 and EEG rhythm generation in schizophrenics. Quantitative EEG (QEEG) in resting condition and P300 during auditory oddball paradigm were recorded with 25 unmedicated patients. Additionally, lateral ventricular-brain ratio (LV-BR), which partially reflects thalamic volume, was measured using CT scan. Brief Psychotic Rating Scale (BPRS) and Scale for Assessment of Negative Symptoms (SANS) were also rated. P300 amplitudes at Pz positively correlated with theta and slow alpha power before pharmacotherapy, however, the correlation tended to be confined to fast alpha after pharmacotherapy. BPRS and SANS showed no significant correlation with QEEG. High frequency bands such as fast alpha and beta showed trends to correlate negatively to LV-BR. The lack of correlation between P300 amplitudes and fast alpha power before pharmacotherapy, which was restored after pharmacotherapy, might indicate thalamocortical dysfunction in schizophrenia.