THE EFFECT OF THE CATECHOL-O-METHYLTRANSFERASE VAL153MET POLYMORPHISM ON TEMPORAL INTERHEMISPHERIC CONNECTIVITY AND LANGUAGE COMPREHENSION IN PATIENTS WITH SCHIZOPHRENIA

Abstract Background Difficulties in language comprehension is the major psychopathology in schizophrenia. The catechol-O-methyltransferase (COMT) Val153Met polymorphism, a candidate gene related to the pathogenesis of schizophrenia, is associated with higher cognitive abilities including language comprehension. At the brain level, this function is known to be supported by reciprocal communication via transcallosal projections between the temporal regions. This study investigated the effect of the COMT Val153Met polymorphism on white matter (WM) integrity of the tapetum, which connects the bilateral temporal lobes, and language comprehension in patients with schizophrenia. Methods Ninety patients with schizophrenia participated in this study. The COMT Val153Met polymorphism was analyzed, and the genotype groups were divided into Val-allele homozygotes and Met-allele carriers (45 participants in each group). Diffusion tensor imaging (DTI) data were acquired from all participants. Fractional anisotropy (FA) values were extracted from the bilateral tapetum. The levels of language comprehension were measured using verbal comprehension subtests of the Korean version of WAIS. Results Val-allele homozygotes showed higher FAs in left tapetum than Met-allele carriers (mean ± SD: val-allele homozygotes = 0.809 ± 0.059, Met-allele carriers = 0.777 ± 0.079; t = 2.16, p = 0.034). The right tapetum FAs were not different between two groups. (mean ± SD: val-allele homozygotes = 0.772 ± 0.065, Met-allele carriers = 0.748 ± 0.061; t = 1.83, p = 0.071). Although the sum of verbal comprehension subtest scores did not differ between two groups, only Val-allele homozygotes showed a negative correlation between the sum scores and left tapetum FAs (val-allele homozygotes: r = -0.426, p = 0.021, Met-allele carriers: r = -0.193, p = 0.275). Discussion This study suggests that the COMT Val153Met polymorphism may be associated with structural changes in interhemispheric WM tracts connecting the temporal regions. Furthermore, COMT-associated WM changes may contribute to individual variations in language comprehension of patients with schizophrenia, particularly Val-allele homozygotes. We expect that our findings provide some clues for understanding the interaction between the brain and genes in patients with schizophrenia.