Public Release:  Gene linked to ADHD allows memory task to be interrupted by brain regions tied to daydreaming


Georgetown University Medical Center






That is important, Gordon says, because dopamine is important for "gating" the transfer of information between brain regions - that is, allowing or preventing new information to come in. "The belief is that dopamine helps teach certain brain regions how and when to gate, and that 10/10 carriers are not gating as quickly or effectively as is possible."








The study was funded by the National Institute of Mental Health.

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603.21/KKK65. Modulation of temporal relationships between default mode and task-positive networks by the dopamine transporter genotype during working memory and the resting state

*E. M. GORDON1, M. STOLLSTORFF1, C. J. VAIDYA1,2; 1Psychology, Georgetown, WASHINGTON, DC; 2Children's Natl. Med. Ctr., Washington, DC.

Human cognitive performance depends on competition between large-scale brain networks such as the default mode network (DMN), implicated in internally oriented cognition, and task-positive networks (TPNs), active during externally oriented cognition. These networks can be identified even in the task-free resting state, suggesting that they represent a stable functional architecture of the brain. Increased competition between networks is associated with more efficient cognition; however, the mechanisms which regulate this competition are unknown. The neurotransmitter dopamine (DA) may help stabilize networks by regulating network competition. We investigated this possibility by examining network relationships associated with natural variation in DA signaling due to polymorphism of the Dopamine Transporter gene (DAT1). Increased synaptic DA is associated with the 9-repeat allele; thus, 9/10 carriers have higher DA signaling than 10/10 carriers. DA differences due to DAT1 are further enhanced by increased DA release during cognitively demanding states (e.g., working memory (WM) performance). If DA signaling helps regulate DMN-TPN relationships, then those relationships should differ between 10/10 and 9/10 carriers during the resting state, and differ even more during WM. To test this possibility, 10/10 and 9/10 carriers underwent functional magnetic resonance imaging during rest and while they performed an N-back WM task. To identify DMN and TPN networks common across all subjects, we conducted a group Independent Components Analysis on the resting data. One resulting network matched the canonical DMN, while three matched canonical TPN regions: a cingulo-opercular (CO) network and right and left frontoparietal (FP) networks. Regions of interest were constructed from these four networks, and for each subject the timecourse of activity within each network was calculated for the rest scan and the WM scan. Temporal correlations between the DMN timecourse and each of the TPN timecourses were calculated and were entered into a Run (rest or WM) X TPN (CO, left FP, or right FP) X DAT (9/10 or 10/10) mixed ANOVA, revealing a significant Run X TPN X DAT interaction. Post-hoc tests showed that the DMN-FP temporal correlations were more positive for 10/10 than for 9/10 carriers during the WM scan, indicating that the 10/10 carriers, who have lower DA signaling, demonstrated less competition between networks, which has been linked to less efficient cognition. However, no network relationships differed by genotype during rest. Thus, DAT genotype affects network competition only when endogenous DA release is high, as in the WM condition.
