Low frequency repetitive transcranial magnetic stimulation improves source monitoring deficit in hallucinating patients with schizophrenia

Auditory hallucinations have been associated with a disruption in monitoring one's own speech suggesting an autonoetic agnosia in schizophrenia. This deficit can be measured by a source monitoring task. Low frequency transcranial magnetic stimulations (rTMS) applied to the left temporoparietal cortex can inhibit cortical areas involved both in autonoetic agnosia (which means 'the inability to identify self-generated mental events') and in auditory hallucinations (AH) phenomena. Although improvements in AH have been repeatedly reported following rTMS treatment, effects on autonoetic agnosia measured by source monitoring have never been investigated. We aimed to investigate the relation between improvements in AH and source monitoring performance after rTMS treatment. Twenty four right-handed refractory schizophrenic patients with hallucinations randomly received sham or active 10.0001-Hz rTMS to the left temporoparietal cortex and performed 2 source monitoring tasks requiring discrimination between silent- and overt-reading words before and after rTMS sessions. Compared to sham, active rTMS significantly improved AH. Source monitoring performances and the improvements tended to correlate, which would support a specific relation between autonoetic agnosia and auditory hallucinations.