An integration of 40 Hz Gamma and phasic arousal: novelty and routinization processing in schizophrenia

Objectives: Frontal and lateralized schizophrenia disturbances were examine d in terms of arousal-modulated changes in 40 Hz Gamma activity. Methods: Forty patients with schizophrenia and 40 age- and gender-matched c ontrols were studied in a conventional auditory ERP oddball paradigm, We in vestigated sub-averaged Gamma activity based upon a simultaneous measure of electrodemal skin conductance response (phasic arousal) to differentiate n ovelty (large responses) from routinization (small or no responses). Both e arly Gamma (Gamma 1) and later induced Gamma (Gamma 2) activities were exam ined. Results: Patients with schizophrenia (compared with controls) had significa ntly reduced Gamma I amplitude in the right hemisphere for novelty processi ng and delayed Gamma 2 latency in the left hemisphere for both novelty and routinization. Overall, reduced Gamma I amplitude in patients with schizoph renia was also evident. Conclusions: These findings indicate that the normal laterality of Gamma ac tivity is specifically disturbed in schizophrenia in response to novel, but not routine (familiar) stimuli. The distinct pattern of findings suggests a dysregulation of activation across left and right hemispheres during init ial attention and preparatory phases of information processing, in particul ar, in patients with schizophrenia. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.