Number of previous studies reported that low-frequency repetitive transcranial magnetic stimulation (rTMS) diminishes treatment-resistant auditory hallucinations. However, little is known about the electrophysiological effect on regional functional activity subsequent to the rTMS treatment.

Eighteen schizophrenic patients with antipsychotic-resistant auditory hallucinations were randomized to either active (n=9) or sham (n=9) rTMS. Low-frequency rTMS (0,9Hz, 100% MP, 1200 stimuli per session) was administered over the left temporo-parietal region for ten days. In case of sham rTMS a coil was tilted at 90°. EEG data were recorded within tree days before and after rTMS treatment. The localization of the differences in electrical activity (current density) was assessed by voxel-by-voxel paired t-tests of the LORETA (low resolution brain electromagnetic tomography) images. The clinical effect was assessed by the Positive and Negative Syndrome Scale (PANSS), Hallucination Change Scale (HCS) and the Auditory Hallucination Rating Scale (AHRS) by a rater blind to the treatment condition.

After two weeks of treatment, both HCS and AHRS scores were significantly improved for patients receiving active rTMS compared to the sham group. LORETA analysis revealed a decrease of current densities in high-frequency bands (alpha 2, beta 1 and beta 2) in the left frontal, temporal and parietal lobes in case of active group. No significant differences in electrical activity were observed in sham group.

Real rTMS but not sham stimulation attenuated an auditory hallucinations and was associated with a decrease of activity in high-frequency bands on the left hemisphere.