Association of high reaction time variability with the 7-repeat allele absence appears to be the most consistent result and seems to be specific to ADHD .
Speed of processing , set-shifting and cognitive impulsiveness were less frequently investigated but seem to be altered in the 7-repeat allele carriers .
High reaction time variability seems to be the most replicated cognitive marker associated with the 10-repeat homozygosity .
BACKGROUND We review ed systematic ally the results of genetic studies investigating associations between putative susceptibility genes for attention-deficit hyperactivity disorder ( ADHD ) and neuropsychological traits relevant for this disorder .
Dissecting the attention deficit hyperactivity disorder (ADHD) phenotype: Sustained attention, response variability and spatial attentional asymmetries in relation to dopamine transporter (DAT1) genotype
ADHD is a childhood-onset behavioural disorder with a heterogeneous profile of neuropsychological impairment . Neuropsychological heterogeneity may , in part , reflect underlying genetic differences . Here we examined sustained attention , response variability and spatial attentional asymmetries in a sample of children and adolescents with ADHD ( n=22 ) in relation to dopamine transporter genotype ( DAT1 ) and also controls ( n=20 ) . Participants performed the sustained attention to response task ( SART ) ( testing sustained attention and response variability ) and the greyscales task ( a perceptual measure of attentional bias ) . The latter has previously been shown to yield a robust leftward attentional asymmetry in healthy subjects . The 10-repeat allele of the DAT1 gene has been associated with ADHD in a number of studies and appears to have biological significance . The ADHD group was sub-divided into those individuals with two copies of the " high-risk " 10-repeat allele ( high-risk DAT1 ) versus those with one or no copies of this allele ( low-risk DAT1 ) . The high-risk DAT1 ADHD group displayed greater response variability on the SART than either the low-risk DAT1 group or healthy controls , whereas the latter two groups did not differ . Further , the high-risk DAT1 group showed an attenuated spatial asymmetry , relative to the low-risk DAT1 ADHD group , who showed the typical leftward attentional asymmetry . Our results suggest that the 10-repeat DAT1 allele may mediate neuropsychological impairment in ADHD . The application of molecular genetics may help to define neuropsychological impaired subgroups of ADHD
Association of high reaction time variability with the 7-repeat allele absence appears to be the most consistent result and seems to be specific to ADHD .
Speed of processing , set-shifting and cognitive impulsiveness were less frequently investigated but seem to be altered in the 7-repeat allele carriers .
High reaction time variability seems to be the most replicated cognitive marker associated with the 10-repeat homozygosity .
BACKGROUND We review ed systematic ally the results of genetic studies investigating associations between putative susceptibility genes for attention-deficit hyperactivity disorder ( ADHD ) and neuropsychological traits relevant for this disorder .