EEG states of the brain, information processing, and schizophrenic primary symptoms.

The electroencephalographic (EEG) reactivity to auditory information (the central component of the orienting reaction) was used to examine brain states underlying information processing in acute and recovered medication-free schizophrenics and matched controls. EEG reactivity was assessed as information-induced changes of parameters extracted from power spectral frequency analysis of the ongoing EEG. EEG reactivity in controls and schizophrenics in remission was largely similar. Acute schizophrenics showed a deviant (ectropic) reactivity, which consisted of changes within the 2-8 Hz band, and of either severely reduced or absent response in the 8-13 Hz (alpha) band. These results indicate an ectropic brain state during cognitive processing of received information during the period of acute schizophrenic symptomatology.