Abnormal angular gyrus asymmetry in schizophrenia

Objective: Few studies have evaluated the parietal lobe in schizophrenia de spite the fact that it has an important role in attention, memory, and lang uage---all functions that have been reported to be abnormal in schizophreni a. The inferior parietal lobule, in particular, is of interest because it i s not only part of the heteromodal association cortex but also is part of t he semantic-lexical network, which also includes the planum temporale. Both the inferior parietal lobule, particularly the angular gyrus of the inferi or parietal lobule, and the planum temporale are brain regions that play a critical role as biological substrates of language and thought. The authors compared volume and asymmetry measures of the individual gyri of the parie tal lobe by means of magnetic resonance imaging (MRI) scans. Method: MRI sc ans with a 1.5-Tesla magnet were obtained from 15 male chronic schizophreni c and 15 comparison subjects matched for age, gender, and parental socioeco nomic status. Results: Inferior parietal lobule volumes showed a leftward a symmetry (left 7.0% larger than right) in comparison subjects and a reverse d asymmetry (left 6.3% smaller than right) in schizophrenic subjects. The a ngular gyrus accounted for this difference in asymmetry, with the left angu lar gyrus being significantly larger (18.7%) than the right in comparison s ubjects, a finding that was not observed in schizophrenic patients. A furth er test of angular gyrus asymmetry showed a reversal of the normal left-gre ater-than-right asymmetry in the schizophrenic patients. Conclusions: Patie nts with schizophrenia showed a reversed asymmetry in the inferior parietal lobule that was localized to the angular gyrus, a structure belonging to t he heteromodal association cortex as well as being part of the semantic-lex ical network. This finding contributes to a more comprehensive understandin g of the neural substrates of language and thought disorder in schizophreni a.