The COMT Val158 allele is associated with impaired delayed-match-to-sample performance in ADHD.
BACKGROUND
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.


METHODS
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.


RESULTS
Significant associations were found between performance on the delayed-match-to-sample task and COMT genotype. More specifically, val/val homozygotes produced significantly more errors than did children who carried a least one met allele. There were no further associations between allelic variants and performance across the other working memory tasks.


CONCLUSIONS
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 met COMT allele and the maintenance of stable working memory representations required to perform the delayed-match-to-sample-task.
The University of Queensland, Queensland Brain Institute and School of Psychology, St Lucia, 4072, Brisbane, Australia. natasha.leigh.matthews@gmail.com
Natasha
N
Matthews
Alasdair
A
Vance
Tarrant D R
TD
Cummins
Joseph
J
Wagner
Amanda
A
Connolly
Jacqueline
J
Yamada
Paul J
PJ
Lockhart
Ajay
A
Panwar
Robyn H
RH
Wallace
Mark A
MA
Bellgrove
D000293:Adolescent; D000483:Alleles; D001289:Attention Deficit Disorder with Hyperactivity / Q000235:genetics*; D002394:Catechol O-Methyltransferase / Q000235:genetics*; D002648:Child; D005260:Female; D014644:Genetic Variation / Q000235:genetics*; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology; D010641:Phenotype; D011930:Reaction Time / Q000235:genetics; D014633:Valine / Q000235:genetics
D002394:Catechol O-Methyltransferase; D014633:Valine