Auditory hallucinations linked to specific gray matter reductions in schizophrenia
MedWire News: A systematic review and meta-analysis of published studies suggests that the severity of auditory hallucinations in patients with schizophrenia is negatively associated with gray matter volume in areas of the brain associated with language.
Writing in Schizophrenia Research, Lena Palaniyappan (Queen's Medical Centre, Nottingham, UK) and team observe that "auditory hallucinations are one of the most common symptoms of schizophrenia."
But they add that studies investigating the neural correlates of auditory hallucinations among schizophrenia patients have produced inconsistent results.
To investigate further, the researchers searched the literature for relevant voxel-based neuroimaging studies.
In total, seven studies involving a total of 350 schizophrenia patients met criteria for inclusion in the final analysis.
Examination of the pooled data revealed that there was significant negative correlation between severity of hallucinations and gray matter volume in two brain area clusters centered on the left insula and right superior temporal gyrus.
The left insular cluster, which extends to Broca's area 44 anteriorly and the superior temporal gyrus posteriorly, showed a significant association in all seven studies.
The right superior temporal gyrus cluster, which extends to the insular region and the subcentral sulcus, showed a significant association in three of the seven studies.
There were no brain areas showing a positive association between auditory hallucinations and gray matter volume, the researchers note.
Palaniyappan and colleagues conclude: "Our findings implicate a major role for the insula along with other regions traditionally regarded as language areas in the pathophysiology of auditory hallucinations."
They add that "a focused exploration of the insula in future using both structural and functional studies in unmedicated samples may help to confirm the insular dysfunction hypothesis in auditory hallucinations."
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By Mark Cowen