Evoked gamma band synchronization and the liability for schizophrenia

Electroencephalographic (EEG) synchronization in the gamma band is thought to represent a neuronal mechanism by which the brain integrates information processed in different cortical areas to build a coherent internal representation. Previous studies have reported abnormal gamma range ( approximately 40 Hz) synchronization in schizophrenic patients. We tested a group of first-degree relatives of schizophrenic probands who have schizophrenia spectrum personality symptoms, and a group of schizophrenic patients, to examine whether individuals with increased liability for schizophrenia have reduced gamma synchronization.

A steady-state auditory evoked potential paradigm was used to evaluate the brain's capacity to sustain 20, 30, and 40 Hz EEG synchronization in 11 relatives, 24 schizophrenic patients (11 on conventional, 13 on new generation antipsychotic medications), and 17 normal controls.

Relatives with schizophrenic spectrum personality symptoms had reduced power at 40 Hz synchronization compared to normal controls (p=0.022). Previous findings of reduced steady-state gamma band synchronization in schizophrenic patients were not directly replicated in this study. Patients as a group did not significantly differ from controls, but patients taking new generation antipsychotics had significantly enhanced 40 Hz synchronization compared to patients taking conventional antipsychotics (p<0.001). There were no group differences in 20 or 30 Hz synchronization.

Gamma band synchronization was found to be reduced in first-degree relatives with schizophrenia spectrum personality symptoms. Patients on new generation antipsychotic medications may exhibit enhanced gamma band synchronization.