Specific and unspecific auditory hallucinations in patients with schizophrenia: a magnetoencephalographic study.

BACKGROUND/AIMS Different neuroimaging techniques have indicated that auditory association and language cortices are active in patients with schizophrenia and auditory hallucinations. Auditory verbal hallucinations are thought to arise from a disorder of inner speech, but little is known about their origin. METHODS Spontaneous magnetoencephalographic (MEG) measurements were recorded with a 74-channel two-sensor system (BIOMAGNES II) in 16 patients with schizophrenia and 8 healthy subjects in frequency ranges from 2 to 6 and 12.5 to 30 Hz. Eight patients had auditory hallucinations during the MEG recordings. RESULTS The total group of patients with schizophrenia showed a statistically significant elevation of the number of dipoles and dipole density maxima in slow frequency ranges compared to healthy subjects (p <0.001). Significant dipole activities in the fast frequency range were only found during auditory hallucinations (p <0.001). Dipole localization was concentrated in frontal and temporal regions depending on different qualities of hallucinations. In patients with external imperative voices we found a parallel activation of the dorsolateral frontal and temporal cortex. CONCLUSION We conclude that various auditory hallucinations in schizophrenia are induced by different neuronal activities and may be represented by different cortical regions.