Hearing voices: a role of interhemispheric auditory connectivity?

OBJECTIVES

Auditory verbal hallucinations (AVH) are among the most common symptoms in schizophrenia. Earlier studies suggest changes in the structural connectivity of auditory areas involved in the pathophysiology of auditory hallucinations. Combining diffusion tensor imaging (DTI) and fibre tractography provides a unique opportunity to visualize and quantify entire fibre bundles.

METHODS

Fibre tracts connecting homotopic auditory areas via the corpus callosum were identified with DTI in ten first episode paranoid schizophrenia patients and ten healthy controls. Regions of interest were drawn manually, to guide tractography, and fractional anisotropy (FA) - a measure of fibre integrity - was calculated and averaged over the entire tract for each subject.

RESULTS

There was no difference in the FA of the interhemispheric auditory fibres between schizophrenic patients and healthy controls. However, the subgroup of patients hearing conversing voices showed increased FA relative to patients without these symptoms (P = 0.047) and trendwise increased FA relative to healthy controls (P = 0.066). In addition, a trendwise correlation between FA values and AVH symptoms (P = 0.089) was found.

CONCLUSIONS

Our findings suggest that in addition to local deficits in the left auditory cortex and disturbed fronto-temporal connectivity, the interhemispheric auditory pathway might be involved in the pathogenesis of AVH.