Distinct linear and non-linear trajectories of reward and punishment reversal learning during development: Relevance for dopamine's role in adolescent decision making
ABSTRACT Abnormalities in value-based decision making during adolescence have often been attributed to non-linear, inverted-U shaped development of reward-related processes. This hypothesis is strengthened by functional imaging work revealing an inverted-U shaped relationship between age and reward-related activity in the striatum. However, behavioural studies have mostly reported linear rather than non-linear increases in reward-related performance. In the present study, we investigated the mechanisms underlying the development of reward- and punishment-related processing across four age groups using a reversal learning task previously shown to depend on striatal dopamine. We demonstrate both linear and non-linear age effects on distinct components of reversal learning. Specifically, results revealed a linear shift with age in terms of valence-dependent reversal learning, with children exhibiting better punishment than reward reversal learning, adults exhibiting better reward than punishment reversal learning and adolescents exhibiting an intermediate performance pattern. In addition, we also observed a non-linear, inverted-U shaped relationship between age and valence-independent reversal learning, which was due to aberrant ability of adolescents to update behaviour in response to negative performance feedback. These findings indicate that the (linear or nonlinear) nature of the relationship between age and reward learning depends on the type of reward learning under study.
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ABSTRACT: Developmental researchers have suggested that adolescents are characterized by stronger reward sensitivity than both children and younger adults. However, at this point, little is known about the extent to which developmental differences in incentive processing influence feedback-based learning. In this study, we applied an incentivized reinforcement learning task, in which errors resulted in losing money (loss condition), failure to gain money (gain condition), or neither (no-incentive condition). Children (10-11 years), younger adolescents (13-14 years), and older adolescents (15-17 years) performed this task while event-related potentials (ERPs) were recorded. We focused our analyses on two ERP correlates of error processing, the error negativity (Ne/ERN) and the error positivity (Pe) that are thought to reflect a rapid preconscious performance monitoring mechanism (Ne/ERN) and conscious detection and/or evaluation of response errors (Pe). Behaviorally, participants in all age groups responded more quickly and accurately to stimuli in gain and loss conditions than to those in the no-incentive condition. The performance data thus did not support the idea that incentives generally have a greater behavioral impact in adolescents than in children. While the Ne/ERN was not modulated by the incentive manipulation, both children and adolescents showed a larger Pe to errors in the gain condition compared to loss and no-incentive conditions. This is in contrast to results from adult studies, in which the Ne/ERN but not the Pe was enhanced for high-value errors, raising the possibility that motivational influences on performance monitoring might be reflected in the activity of separable neural systems in children and adolescents vs. adults. In contrast to the idea of higher reward/incentive sensitivity in adolescents, our findings suggest that incentives have similar effects on feedback-based learning from late childhood into late adolescence with no changes in preferences for "trick over treat."Frontiers in Psychology 09/2014; 5:968. DOI:10.3389/fpsyg.2014.00968 · 2.80 Impact Factor
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ABSTRACT: It is widely accepted that brain maturation from adolescence to adulthood contributes to substantial behavioural changes. Despite this, however, knowledge of the precise mechanisms is still sparse. We used fMRI to investigate developmental differences between healthy adolescents (age range 14–15) and adults (age range 20–39) in feedback-related decision making using a probabilistic reversal learning task. Conventionally groups are compared based on continuous values of blood oxygen level dependent (BOLD) percentage signal change. In contrast, we transformed these values into discrete states and used the pattern of these states to compare groups. We focused our analysis on anterior cingulate cortex (ACC), ventral striatum (VS) and ventromedial prefrontal cortex (vmPFC) as their functions have been shown to be critical in feedback related decision making. Discretisation of continuous BOLD values revealed differential patterns of activity as compared to conventional statistical methods. Results showed differential representation of feedback and decision in ACC and vmPFC between adolescents and adults but no difference in VS. We argue that the pattern of activity of ACC, vmPFC and VS in adolescents resulted in several drawbacks in decision making such as redundant and imprecise representation of decision and subsequently poorer performance in terms of the number of system changes (change of contingencies). This method can be effectively used to infer group differences from within-group analysis rather than studying the differences by direct between-group comparisons.Neuropsychologia 04/2014; 56. DOI:10.1016/j.neuropsychologia.2014.01.021 · 3.45 Impact Factor
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ABSTRACT: It has been suggested that adolescents process rewards differently from adults, both cognitively and affectively. In an fMRI study we recorded brain BOLD activity of adolescents (age range = 14-15) and adults (age range = 20-39) to investigate the developmental changes in reward processing and decision-making. In a probabilistic reversal learning task, adolescents and adults adapted to changes in reward contingencies. We used a reinforcement learning model with an adaptive learning rate for each trial to model the adolescents' and adults' behavior. Results showed that adolescents possessed a shallower slope in the sigmoid curve governing the relation between expected value (the value of the expected feedback, +1 and -1 representing rewarding and punishing feedback, respectively) and probability of stay (selecting the same option as in the previous trial). Trial-by-trial change in expected values after being correct or wrong was significantly different between adolescents and adults. These values were closer to certainty for adults. Additionally, absolute value of model-derived prediction error for adolescents was significantly higher after a correct response but a punishing feedback. At the neural level, BOLD correlates of learning rate, expected value, and prediction error did not significantly differ between adolescents and adults. Nor did we see group differences in the prediction error-related BOLD signal for different trial types. Our results indicate that adults seem to behaviorally integrate punishing feedback better than adolescents in their estimation of the current state of the contingencies. On the basis of these results, we argued that adolescents made decisions with less certainty when compared with adults and speculated that adolescents acquired a less accurate knowledge of their current state, that is, of being correct or wrong.Journal of Cognitive Neuroscience 06/2014; 26(12):1-12. DOI:10.1162/jocn_a_00677 · 4.69 Impact Factor