Indication of increased phase coupling between theta and gamma EEG rhythms associated with the experience of auditory verbal hallucinations

Electroencephalographic oscillations, with different spectral contents, recorded in various brain sites are assumed to play an important role in the information processes underlying cognition as well as the abnormal brain functioning observed in nosological entities that affect neuronal connectivity such as schizophrenia. In the present study we investigated the interaction of EEG rhythms during the experience of auditory verbal hallucinations (AVHs). For this purpose we analyzed data obtained from patients suffering from persistent AVHs, focusing on the mode that the phase of theta oscillations modulate the amplitude of the broad gamma EEG oscillations. Our results indicate increased phase coupling between theta and gamma rhythms observed in the left frontotemporal cortices during AVHs, under eyes closed condition. The average differences of theta-gamma coupling between hallucinatory and resting stages in the left temporal area were found to be statistically significant. These results suggest that a theta-gamma interaction may be involved in the production and experience of AVHs in patients suffering from schizophrenia.

► Synergy between theta and gamma EEG rhythms is associated with cognitive processes. ► Auditory verbal hallucinations are considered to be autonomous cognitive processes. ► Theta-gamma EEG rhythms interaction was found during auditory verbal hallucinations.