Adolescent impatience decreases with increased frontostriatal connectivity

Abstract

Adolescence is a developmental period associated with an increase in impulsivity. Impulsivity is a multidimensional construct, and in this study we focus on one of the underlying components: impatience. Impatience can result from (i) disregard of future outcomes and/or (ii) oversensitivity to immediate rewards, but it is not known which of these evaluative processes underlie developmental changes. To distinguish between these two causes, we investigated developmental changes in the structural and functional connectivity of different frontostriatal tracts. We report that adolescents were more impatient on an intertemporal choice task and reported less future orientation, but not more present hedonism, than young adults. Developmental increases in structural connectivity strength in the right dorsolateral prefrontal tract were related to increased negative functional coupling with the striatum and an age-related decrease in discount rates. Our results suggest that mainly increased control, and the integration of future-oriented thought, drives the reduction in impatience across adolescence.adolescence | connectivity | impatience | delay discounting | DTI

Multiple accounts of adolescent impulsivity

“…As we and others have reported in previous studies (7), van den Bos et al (1) find that adolescents are more likely than adults to opt for smaller rewards sooner (SS) than larger ones later (LL). The authors posit that the extent to which individuals are inclined toward SS choices indexes impatience, which they view as one of three aspects of impulsivity (the other two are acting without thinking and sensation-seeking).…”

“…At the turn of the 21st century, research on the development of self-control in adolescence added functional brain imaging as a complement to behavioral tasks and self-report questionnaires, but the essential question has remained the same: Why do teenagers have so much difficulty controlling their impulses? As a report in PNAS by van den Bos et al (1) attests, the question continues to be of interest. Although we discuss some potential limitations, the study these authors describe adeptly and cleverly incorporates the broad armamentarium of tools, including self-report, behavior, brain function, and both structural and functional connectivity measures, to move us toward a more complete answer to the question.…”

“…It is important to put the contributions of van den Bos et al (1) in historical context. Ten years ago, the pat explanation for adolescent impulsivity was the immaturity of the prefrontal cortex.…”

“…This is an important analysis that didn't make its way into the current paper (1). The authors conclude that it is "increased control, not sensitivity to immediate rewards, that drives developmental reductions in impatience," but the latter construct may not have been adequately assessed (1).…”

“…Finally, van den Bos et al (1) argue that, because the degree of frontostriatal connectivity observed is correlated with a stronger preference for LL choices, and that this connectivity increases with age, it must be weaker cognitive control that accounts for adolescents' relatively greater propensity for SS choices. The authors provide evidence in support of this hypothesis by showing that there is a significant indirect pathway linking age and intertemporal preferences that is mediated by the strength of connectivity between the dorsolateral prefrontal cortex and the medial striatum.…”