ADHD Subtype Differences in Motivational Responsivity but not Inhibitory Control: Evidence From a Reward-Based Variation of the Stop Signal Paradigm

Abstract

In this study we examined prepotent motor inhibition and responsiveness to reward using a variation of the stop signal reaction time (SSRT) task in clinic- and community-recruited children ages 7 to 12 with attention-deficit/hyperactivity disorder–inattentive type (ADHD–I), ADHD–combined type (ADHD–C), and non-ADHD controls. Contrary to theoretical expectations, we found evidence for inhibitory weaknesses in ADHD–I. We also found evidence that although children with ADHD–I were able to improve their inhibitory control given reward-based motivation, the improvement depended on the order of reward conditions. Results suggest that the 2 primary subtypes of ADHD share similar neuropsychological weaknesses in inhibitory control but that there are subtype differences in response to success and failure that contribute to a child's ultimate level of performance.

Notes

Note: p values obtained by omnibus analyses of variance without covariates. Within each row, where subscripts are identical, no group differences were found. Conversely, where subscripts are dissimilar, group differences in the means for that variable were found. ADHD–I = attention deficit hyperactivity disorder–inattentive type; ADHD–C = attention deficit hyper actitivity disorder–combined type; CSI = Child Symptom Inventory; SCT = Sluggish Cognitive tempo; ODD = oppositional defiant disorder; CD = conduct disorder.

^a n = 36

^b n = 33

^c n = 23

Note: p values obtained by omnibus analyses of variance without covariates. Within each row, where subscripts are identical, no group differences were found. Conversely, where subscripts are dissimilar, group differences in the means for that variable were found. ADHD–I = attention deficit hyperactivity disorder –inattentive type; ADHD–C = attention deficit hyperactivity disorder–combined type; MRT = mean reaction time, SSRT = stop signal reaction time.