Mapping the genetic variation of executive attention onto brain activity

Abstract

Brain imaging data have repeatedly shown that the anterior cingulate cortex is an important node in the brain network mediating conflict. We previously reported that polymorphisms in dopamine receptor (DRD4) and monoamine oxidase A (MAOA) genes showed significant associations with efficiency of handling conflict as measured by reaction time differences in the Attention Network Test (ANT). To examine whether this genetic variation might contribute to differences in brain activation within the anterior cingulate cortex, we genotyped 16 subjects for the DRD4 and MAOA genes who had been scanned during the ANT. In each of the two genes previously associated with more efficient handling of conflict in reaction time experiments, we found a polymorphism in which persons with the allele associated with better behavioral performance showed significantly more activation in the anterior cingulate while performing the ANT than those with the allele associated with worse performance. The results demonstrate how genetic differences among individuals can be linked to individual differences in neuromodulators and in the efficiency of the operation of an appropriate attentional network.

Fig. 1.

Genetic variation in MAOA and DRD4 and executive attention. The y axis of a and b shows the ratio conflict scores: (incongruent RT - congruent RT) divided by mean RT. The x axis in a and c indicates that subjects were grouped according to whether they were homozygous/hemizygous for the four-repeat allele of the MAOA LPR (four-repeat class, n = 55) or, alternatively, whether they were homozygous/hemizygous or heterozygous for the MAOA LPR (three-repeat class, n = 115). The x axis in b and d indicates that subjects were grouped according to whether they were homozygous for the insertion of a guanosine residue at position -1217 (insertion class, n = 112) or whether they were heterozygous for the “G” insertion/deletion polymorphism at this site (delection class, n = 71). The y axis of c and d is the conflict score based on the error/incongruent error rate - congruent error rate. (Error bar = ± 1 SE.)

Fig. 2.

Genetic variation in MAOA and DRD4 and brain activity. (a) Greater brain activity among subjects who were grouped according to genotype at the MAOA LPR four-repeat class (n = 8) in comparison with three-repeat class (n = 8). (b) Greater brain activity among subjects who were grouped according to genotype at the DRD4 insertion class (n = 6) in comparison with deletion class (n = 10). The color bar represents the level of t value. (c and d) The y axis shows the conflict effect based on the difference between incongruent and congruent conditions on ratio scores of RT for subjects in the corresponding genetic groups. (e and f) The y axis shows the error rate differences between incongruent and congruent conditions for each genetic group. (Error bar = ± 1 SE.)