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Modifying Brain Networks 415Not all children need or benefit from attention training. This may be why variabilityis so high. In some of our studies we found that those children with themost initial difficulty in resolving conflict showed the greatest overall improvementdue to training. Our research has also suggested a genetic marker of difference inattention among children. A dopamine-related gene, the dopamine transporter 1(DAT1) gene, has been shown to be related to the efficiency of the executive attentionnetwork (Fossella et al., 2002). We were able to genotype most of the 6-yearoldchildren who participated in our training study. Children were divided intotwo groups according to their particular form of the DAT1 gene, those carryingthe pure long form and those carrying the pure short or mixed short/long forms ofthe gene. Because our sample was small, we combined 6-year-olds who had attentiontraining with those in the control condition. Performance was examinedon the first and second ANT. Although there were only seven children in the purelong allele group and eight in the mixed long/short group, we found a significantadvantage in conflict scores for the pure long allele group.Several features of our data supported the relation between the DAT1 polymorphismand individual differences in the efficiency of executive attention. Childrenin the two groups differed in their conflict scores as well as in the effortfulcontrol scores obtained with the parent-reported temperament questionnaires evenbefore any training. In particular, the short/long mixed group showed higher conflictscores and lower effortful control than those in the pure long group. The twogroups also differed in their EEG data. In the first session, the children with thepure long allele showed the effect of flankers in the expected direction (morenegative N2 for incongruent condition, as shown in figure 18-4), whereas childrenin the mixed alleles group did not show such an effect. This difference correspondsto the trend we found for development between 4 and 6 years of age andto the effect of training, and suggests that the pure long form is associated withmore mature executive attention.The DAT1 gene has also been associated with ADHD; however, the exact relationbetween executive attention efficiency in normals and the presence of attentiondeficits in ADHD is not clear (Swanson, Oosterlaan, Murias, Moyzis,Schuck, et al., 2000).Given the wide range of differences among individuals in the efficiency of attention,it is expected that attention training could be especially beneficial for thosechildren with poorer initial efficiency. These could be children with pathologiesthat involve attentional networks, children with particular genetic backgroundsassociated with poorer attentional performance, or children raised in differentdegrees of deprivation.SummaryIn this part of our paper, we have summarized evidence that attention training at 4and 6 years of age can modify the functioning of networks involved in self-regulation.