S.S. Shergill, M.J. Brammer, R. Fukuda, S.C. Williams, R.M. Murray, and P.K. McGuire, British Journal of Psychiatry, June 2003, 182, 525–31.
BACKGROUND: The neurocognitive basis of auditory hallucinations is unclear, but there is increasing evidence implicating abnormalities in processing inner speech. Previous studies have shown that people with schizophrenia who were prone to auditory hallucinations demonstrated attenuated activation of brain areas during the monitoring of inner speech.
AIMS: To investigate whether the same pattern of functional abnormalities would be evident as the rate of inner speech production was varied.
METHOD: Eight people with schizophrenia who had a history of prominent auditory hallucinations and eight control participants were studied using functional magnetic resonance imaging while the rate of inner speech generation was varied experimentally.
RESULTS: When the rate of inner speech generation was increased, the participants with schizophrenia showed a relatively attenuated response in the right temporal, parietal, parahippocampal and cerebellar cortex.
CONCLUSIONS: In people with schizophrenia who are prone to auditory hallucinations, increasing the demands on the processing of inner speech is associated with attenuated engagement of the brain areas implicated in verbal self-monitoring.