Brain activation to cues predicting inescapable delay in adolescent Attention Deficit/Hyperactivity Disorder: an fMRI pilot study

Abstract

Background: The choice of small immediate over large delayed rewards (i.e., impulsive choice) is a signal marker of motivational style in Attention Deficit/Hyperactivity Disorder (ADHD). The delay aversion model proposes that, in part, this is a conditioned delay avoidance response. Here we test the prediction derived from this model that, in ADHD, cues predicting inescapable delay differentially activate brain regions shown previously to be responsive to motivationally salient, negatively valenced environmental events.

Methods: Ten adolescents with ADHD and 10 age matched controls performed a simple speeded reaction time task under two conditions. On Escape Delay trials slow responses only were punished by the imposition of post-response delay periods. On No Escape Delay trials post-response delay occurred on all trials irrespective of response speed. Using functional Magnetic Resonance Imaging (fMRI) BOLD responses were acquired to compare anticipatory brain activation following the two cue types. ROI analyses found significant ADHD-related hyperactivation following No Escape compared to Escape Delay trial cues in the insula, amygdala, ventral striatum and orbito-frontal cortex.

Conclusion: The results of this pilot study provide further evidence for the role of altered motivational systems in ADHD and the most direct evidence for a biological basis of delay aversion.