A large body of literature supports the hypothesis that high frequency oscillations within the gamma band are involved in the integration of sensory information across different modalities and cortical areas. A reduction of gamma oscillations around 40 Hz has been reported in schizophrenic patients by several authors. This abnormality indicates a poor integration of the neuronal activity within distributed neural networks in schizophrenia, in line with modern conceptualizations of the disorder and its liability.

In the present study we investigated evoked and induced 40-Hz gamma power as well as fronto-parietal and fronto-temporal event-related coherence in patients with deficit and nondeficit schizophrenia and in matched healthy controls. In patients, correlations between gamma oscillations and psychopathological dimensions were also investigated.

We found that abnormalities of both induced gamma power and event-related coherence were present in patients with nondeficit schizophrenia, but not in those with deficit schizophrenia. These findings suggest that schizophrenia heterogeneity should be taken into account when dealing with indices of cortical functional connectivity.

In line with previous findings, in our study an excess of gamma oscillations has been found to correlate with reality distortion and other psychopathological dimensions, indicating that abnormal thoughts, behaviours and perceptions might be related to abnormal connectivity within distributed neural networks.