Measuring "waiting" impulsivity in substance addictions and binge eating disorder in a novel analogue of rodent serial reaction time task

Abstract

Background: Premature responding is a form of motor impulsivity that preclinical evidence has shown to predict compulsive drug seeking but has not yet been studied in humans. We developed a novel translation of the task, based on the rodent 5-choice serial reaction time task, testing premature responding in disorders of drug and natural food rewards.

Methods: Abstinent alcohol- (n = 30) and methamphetamine-dependent (n = 23) subjects, recreational cannabis users (n = 30), and obese subjects with (n = 30) and without (n = 30) binge eating disorder (BED) were compared with matched healthy volunteers and tested on the premature responding task.

Results: Compared with healthy volunteers, alcohol- and methamphetamine-dependent subjects and cannabis users showed greater premature responding with no differences observed in obese subjects with or without BED. Current smokers exhibited greater premature responding versus ex-smokers and nonsmokers. Alcohol-dependent subjects also had lower motivation for explicit monetary incentives. A Motivation Index correlated negatively with alcohol use and binge eating severity.

Conclusions: Premature responding on a novel translation of a serial reaction time task was more evident in substance use disorders but not in obese subjects with or without BED. Lower motivation for monetary incentives linked alcohol use and binge eating severity. Our findings add to understanding the relationship between drug and natural food rewards.

Keywords: Binge eating; impulsivity; motivation; obesity; premature responding; substance use disorders.

Figure 1

Premature responding task. (A) Task. Subjects press and hold down the space bar when they see four empty boxes (Cue) on the touch screen. After a green circle (Target) appears in one of the boxes, the subject releases the space bar and touches the box in which the target had appeared. The main outcome measure, premature responding, is measured as release of the space bar before target onset. (B) Feedback for the Test blocks is individualized on the basis of the mean fastest reaction time (RT) and SD obtained in the Baseline block.

Figure 2

Premature responding and motivation index. (A) Premature responses in abstinent alcohol- (EtOH) (n = 30) and methamphetamine-dependent (Meth) (n = 23) subjects, recreational cannabis users (Cann) (n = 30), and obese subjects with binge eating disorder (BED) (n = 30) (Index group = red) versus healthy volunteers (HV) (black) and obese control subjects without BED (white) (n = 30). (B) Premature responses in current and past HV smokers and nonsmokers. (C) Motivation Index in EtOH (n = 30) versus HV. Error bars represent SEM. *p < .05; **p < .005.