Life Sciences Division

“Where do the voices come from?”: anatomy of the schizophrenic brain

CEA

Why is it that some schizophrenic patients hear voices inside their head whereas others claim the voices come from outside? A CEA-Inserm research team from I²BM working collaboratively with the psychiatric wards at Sainte-Anne hospital and the Chenevier-Henri Mondor and Cochin-St-Vincent de Paul (AP-HP) hospital centres has shown that this split in the source of voices heard can be explained by anatomic difference in the brain, within a region that is involved in the spatial localization of sound.

WHO figures assert that around 1% of the world’s population is affected by schizophrenia. It has many clinical symptoms. Verbal auditory hallucinations, i.e. hearing voices, is one of the most frequent symptoms, with 70% of patients affected. In 20% of cases, none of the available therapeutic strategies are effective. Deeper insight into the mechanisms underlying these treatment-resistant auditory hallucinations could open up new perspectives for therapy. The results of this collaborative research were published online on the 7 August 2009 issue of Schizophrenia Bulletin.

The original work by Bleuler and Kraepelin led to schizophrenic auditory hallucinations being classified into one of two groups: those where patients hear voices in their head, and those where they hear voices from outside. This clinical distinction prompted the research team to investigate the in-brain mechanisms involved in the spatial localization of treatment-resistant auditory hallucinations.

A comparative study conducted using anatomical brain MRI* on 20 healthy volunteers and two groups of schizophrenic patients, each suffering from one of the two types of auditory hallucinations (12 patients only hearing voices from outside and 15 only hearing voices inside their head) highlighted a difference in the brain region involved in the spatial localization of sound (the right temporo-parietal cortex). The team studied the anatomy of this region using sophisticated high-tech 3D image analysis methods developed at NeuroSpin. Their analysis revealed an anomaly at the junction between two of the furrow-like cortical sulci: the superior temporal gyrus and the angular gyrus (image left). In more specific terms, compared to healthy subjects, in the group that heard voices from outside their head (shown in pink on the image right) the junction was significantly farther to the front of the brain, whereas in the group that heard voices inside their head (shown in blue on the image right) it was significantly farther to the rear.

This positional difference in the gyrus junction could flag variances in brain growth during brain maturation in the third trimester of pregnancy, when these two sulci first take form and then interconnect. These results suggest that brain anatomy is potentially a factor in the expression of a phenomenon as subjective and intimate as where voices come from in schizophrenia. This offers yet another reason to stop stigmatizing schizophrenia patients, as they are suffering from what remains a poorly-understood disease.

• Magnetic resonance imaging: applying a combination of high-frequency electromagnetic waves to a part of the body and measuring the signal re-emitted by certain atoms (including hydrogen) makes it possible to determine the chemical composition – and therefore the characteristics – of body tissues at each point in the volume scanned.