Neural Hyporesponsiveness and Hyperresponsiveness During Immediate and Delayed Reward Processing in Adult Attention-Deficit/Hyperactivity Disorder

Frequencies of choosing the early reward option and decision times separated by the delay-to-delivery levels. (A) Healthy control subjects and ADHD patients did not differ significantly with respect to choices of smaller/earlier rewards. Numerically, ADHD patients chose the smaller/earlier reward option more frequently when it was delivered immediately (p = .07). Asterisk indicates significant group differences at a level of p < .05. (B) While healthy control subjects showed nearly invariant decision times, ADHD patients were significantly slower during delayed compared with immediate reward trials (p < .05). ADHD, attention-deficit/hyperactivity disorder.

Ventral striatum/nucleus accumbens hyporesponsiveness in ADHD. (A) Mean beta estimates on immediate and delayed rewards (averaged over significant voxels and hemispheres). Asterisks indicate significant group differences at a level of p < .05. Within-group comparisons between immediate and delayed rewards demonstrated a significant effect for both groups separately (p < .05). (B) Significant ventral striatal/nucleus accumbens hyporesponsiveness toward rewards independent of the delay-to-delivery level in the ADHD group. ADHD, attention-deficit/hyperactivity disorder; BOLD, blood oxygenation level-dependent; NAcc, nucleus accumbens; VS, ventral striatum.

Graded neural responses toward different delay-to-delivery levels within the reward system. (A) The significant interaction cluster shown slicewise in its ventral-to-dorsal extent. (B) Corresponding to each z-slice, group response differences (mean parameter estimates averaged over significant voxels of both hemispheres; ADHD minus control subjects) toward immediate and delayed rewards are shown. The interaction effect consists of two distinct effects: as compared with healthy control subjects, ADHD patients show 1) ventral striatal hypoactivation toward immediate rewards; and 2) dorsal striatal hyperactivation toward delayed rewards. (C) The corresponding mean BOLD time courses. ADHD, attention-deficit/hyperactivity disorder; BOLD, blood oxygenation level-dependent.

(A) Mean parameter estimates of BOLD responses averaged over subjects and hemispheres separated for the delay-to-delivery levels in the amygdala (B). BOLD, blood oxygenation level-dependent.

Correlation of ADHD symptom severity (ASRS self-ratings of hyperactivity/impulsivity; mean corrected) with differential BOLD responses (delayed minus immediate; individual mean differences of parameter estimates averaged over hemispheres; mean corrected) in the dorsal caudate (left panel) and amygdala (right panel). ADHD, attention-deficit/hyperactivity disorder; ASRS, Adult ADHD Self-Report Scale; BOLD, blood oxygenation level-dependent.

(A) Group differences on the valence decay score (for calculation, see Methods and Materials). Asterisk indicates significant group differences at a level of p < .05. (B) Correlation of individual valence decay scores (mean corrected) with differential BOLD responses (delayed minus immediate; individual mean differences of parameter estimates averaged over hemispheres; mean corrected) in the amygdala. ADHD, attention-deficit/hyperactivity disorder; BOLD, blood oxygenation level-dependent.