A unique adolescent response to reward prediction errors

Abstract

Previous work has shown that human adolescents may be hypersensitive to rewards, but it is not known which aspect of reward processing is responsible for this. We separated decision value and prediction error signals and found that neural prediction error signals in the striatum peaked in adolescence, whereas neural decision value signals varied depending on how value was modeled. This suggests that heightened dopaminergic prediction error responsivity contributes to adolescent reward seeking.

Figure 1

Experimental design. 45 healthy participants (18 children aged 8–12, 16 adolescents aged 14–19, and 11 adults aged 25–30) performed a probabilistic learning task during fMRI acquisition. Written informed consent was obtained. Participants classified abstract stimuli into one of two categories (Northern and Eastern) and were given feedback displaying the correct response at the end of each trial. If their response matched the outcome, feedback included a monetary reward. We paid participants based on the reward they received to ensure motivation. There were two stimulus types: predictable (associated 83% of the time with one of the two categories) and random (associated 50% of the time with each category). There were also two magnitudes of reward: large rewards (25 cents) and small rewards (5 cents).

Figure 2

MRI results. (a) Regions showing correlations with age when correcting at the whole-brain level at z > 2.3, P< 0.05. The striatal and angular gyrus regions were negatively correlated with age²; because the mean age² was subtracted from each value prior to squaring, age² is lowest for adolescents, and thus the negative correlation reflects greater signals for adolescents. The region in the medial prefrontal cortex was negatively correlated with age. For cluster details see Supplementary Table 4 online. PE = prediction error; DV = decision value. (b) Striatal ROI analyses cluster-mass corrected at z > 2.3, P< 0.05. When looking at the striatal response to prediction error separately for the three age groups, we saw different striatal regions active for adolescents (red) and adults (blue). Children showed no activity, even when lowering the threshold to uncorrected P< 0.05. For direct comparisons across groups of feedback- and prediction error-related striatal responses, see Supplementary Figs. 8–9 online.