Audio-visual speech perception in schizophrenia: an fMRI study

Abnormalities in the integration of auditory and visual language inputs cou ld underlie many core psychotic features. Perceptual confusion may arise be cause of the normal propensity of visual speech perception to evoke auditor y percepts. Recent functional neuroimaging studies of normal subjects have demonstrated activation in auditory-linguistic brain areas in response to s ilent lip-reading. Three functional magnetic resonance imaging experiments were carried out on seven normal volunteers, and 14 schizophrenia patients, half of whom were actively psychotic. The tasks involved listening to audi tory speech, silent Lip-reading (visual speech), and perception of meaningl ess lip movements (visual non-speech). Subjects also undertook a behavioura l study of audio-visual word identification designed to evoke perceptual fu sions. Patients and controls both showed susceptibility to audio-visual fus ions on the behavioural task. The patient group as a whole showed less acti vation relative to controls in superior and inferior posterior temporal are as while performing the silent lip-reading task. Attending to visual non-sp eech, the patients activated less posterior (occipito-temporal) and more an terior (frontal, insular and striatal) brain areas than controls. This diff erence was accounted for Largely by the psychotic subgroup. Insular and str iatal areas were also activated in both subject groups in the auditory spee ch perception condition, thus demonstrating the bimodal sensitivity of thes e regions. The results suggest that schizophrenia patients with psychotic s ymptoms respond to visually ambiguous stimuli (non-speech) by activation of polysensory structures. This could reflect particular processing strategie s and may increase susceptibility to certain paranoid and hallucinatory sym ptoms. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.