Catechol-O-methyltransferase (COMT) genotypes and working memory: Associations with differing cognitive operations

Background: Catechol-O-methyltransferase (COMT) is a strong candidate gene for schizophrenia and cognitive functions disrupted in this disorder. The report examines the relation examines the relation of COMT genotypes to performance on a batteryof working memory tests differening on the cognitive operations to be performed on the material. Methods: A large sample of 402 healthy adults were tested on four working memory tests: Spatial Delayed Response (SDR), Word Serial Position Test (WSPT), N-back, and Letter-Number Sequencing. A subsample (n = 246) was tested on the Wisconsin Card Sorting Test (WCST). A saliva swab was used to obtain DNA from all participants. Results: Letter-Number Sequencing, which requires both storage and manipulation of information, was the only working memory test that showed expected differences among COMT genotypes, with the met/met group also performed better than the val/val group on the WCST. Conclusion: COMT genotypes were not associated with performance on tests measuring simple storage, maintenance of temperol order or updating of information in working memory. Genotype differences in Letter-Number Sequencing and WSCT suggest that higher-order components of processing (e.g., mental manipulation) are more closely related to this gene.