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 .
Development of cognitive control and executive functions from 4 to 13 years: Evidence from manipulations of memory, inhibition, and task switching
Predictions concerning development , interrelations , and possible independence of working memory , inhibition , and cognitive flexibility were tested in 325 participants ( roughly 30 per age from 4 to 13 years and young adults ; 50 % female ) . All were tested on the same computerized battery , design ed to manipulate memory and inhibition independently and together , in steady state ( single-task blocks ) and during task-switching , and to be appropriate over the lifespan and for neuroimaging ( fMRI ) . This is one of the first studies , in children or adults , to explore : ( a ) how memory requirements interact with spatial compatibility and ( b ) spatial incompatibility effects both with stimulus-specific rules ( Simon task ) and with higher-level , conceptual rules . Even the youngest children could hold information in mind , inhibit a dominant response , and combine those as long as the inhibition required was steady-state and the rules remained constant . Cognitive flexibility ( switching between rules ) , even with memory dem and s minimized , showed a longer developmental progression , with 13-year-olds still not at adult levels . Effects elicited only in Mixed blocks with adults were found in young children even in single-task blocks ; while young children could exercise inhibition in steady state it exacted a cost not seen in adults , who ( unlike young children ) seemed to re-set their default response when inhibition of the same tendency was required throughout a block . The costs associated with manipulations of inhibition  were greater in young children while the costs associated with increasing memory dem and s were greater in adults . Effects seen only in RT in adults were seen primarily in accuracy in young children . Adults slowed down on difficult trials to preserve accuracy ; but the youngest children were impulsive ; their RT remained more constant but at an accuracy cost on difficult trials . Contrary to our predictions of independence between memory and inhibition , when matched for difficulty RT correlations between these were as high as 0.8 , although accuracy correlations were less than half that . Spatial incompatibility effects and global and local switch costs were evident in children and adults , differing only in size . Other effects ( e.g. , asymmetric switch costs and the interaction of switching rules and switching response-sites ) differed fundamentally over age
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 .