| Summary: | <p>Abstract</p> <p>Background</p> <p>This study explored the association between three measures of working memory ability and genetic variation in a range of catecholamine genes in a sample of children with ADHD.</p> <p>Methods</p> <p>One hundred and eighteen children with ADHD performed three working memory measures taken from the CANTAB battery (Spatial Span, Delayed-match-to-sample, and Spatial Working Memory). Associations between performance on working memory measures and allelic variation in catecholamine genes (including those for the noradrenaline transporter [NET1], the dopamine D4 and D2 receptor genes [DRD4; DRD2], the gene encoding dopamine beta hydroxylase [DBH] and catechol-O-methyl transferase [COMT]) were investigated using regression models that controlled for age, IQ, gender and medication status on the day of test.</p> <p>Results</p> <p>Significant associations were found between performance on the delayed-match-to-sample task and COMT genotype. More specifically, <it>val/val</it> homozygotes produced significantly more errors than did children who carried a least one <it>met</it> allele. There were no further associations between allelic variants and performance across the other working memory tasks.</p> <p>Conclusions</p> <p>The working memory measures employed in the present study differed in the degree to which accurate task performance depended upon either the dynamic updating and/or manipulation of items in working memory, as in the spatial span and spatial working memory tasks, or upon the stable maintenance of representations, as in the delay-match–to-sample task. The results are interpreted as evidence of a relationship between tonic dopamine levels associated with the <it>met</it> COMT allele and the maintenance of stable working memory representations required to perform the delayed-match-to-sample-task.</p>
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