Padmanabhan, A., Geier, C. F., Ordaz, S. J., Teslovich, T., & Luna, B. (2011). Developmental changes in brain function underlying the influence of reward processing on inhibitory control. Developmental cognitive neuroscience, 1(4), 517-529.
Background: Previous work has found that (a) despite exhibiting adult levels of inhibitory control, adolescents show differential engagement of task control regions compared to adults, and (b) adolescents show differences from adults in ventral striatum and prefrontal engagement during reward processing. At the time this paper was written, little work had been done to investigate the influence of motivational (monetary) incentives on cognitive control in adolescence. The goal was to compare behavioral performance and brain activity during a rewarded inhibitory control task between children, adolescents, and adults.
Methods: 10 children (8-13yrs), 10 adolescents (14-17yrs), and 10 adults (18-25yrs) played an antisaccade task (eyetracking) where cues indicated if each trial would be rewarded or not. Variables of interest in the antisaccade task: latencies in correct AS trials and error rate (num failures/total trials). They ran a repeated measures ANOVA on the timecourses from a priori ROIs (paracentral sulcus (supplementary eye field; SEF), superior precentral sulcus (frontal eye field; FEF), SPL (parietal eye field; PEF), dorsal striatum, ventral striatum).
Behavioral Results: More errors were made during the neutral trials than the rewarded trials. Children and adolescents had more errors than adults. Children and adolescents improved in their performance during rewarded compared to neutral trials (adults showed no significant effect of reward condition). No differences between children, adolescents, and adults performance during the rewarded trials. All groups had shorter latencies during rewarded compared to neutral trials.
Imaging Results:
- Children > everybody else: supplementary eye field, dorsal ACC
- Adolescents > everybody else: right IPS, bilateral putamen, bilateral ventral striatum
Discussion: There are two key findings: (1) rewards enhance inhibitory control performance (decreased latencies and error rates) in children and adolescence such that their behavior is indistinguishable from adults. This could reflect a heightened sensitivity to external rewards than adults. (2) Neural circuitry supporting inhibitory control and reward processing is in place by childhood, but there are differences in regional engagement across development. Adolescents engaged response planning and reward regions (IPS and putamen) more than adults and children. Children exhibited similar brain activation to adults in ventral striatum, putamen and IPS, which suggests functional development in an inverted U curve shape. Children’s greater engagement of the supplementary eye field and dorsal ACC compared to adolescents and adults could reflect the use of a compensatory mechanism to complete the inhibitory control task.
Thoughts:
- I was struck by the authors statement that “adolescent behavior is distinct from childhood and adulthood as evidenced by heightened incidents of sub-optimal or immature decision-making.” Is it that adolescents make worse decisions than children or that adolescents have greater independence and access to risky contexts than children do?
- I am intrigued by the idea that adolescents can exhibit adult levels of inhibitory control but inconsistently. Has someone used frequency analyses (i.e. Fast Fourier Transform) to look at developmental differences in response time?
- The antisaccade task they used interspersed rewarded and neutral (non-rewarded trials). Is this beneficial in that it incorporates a layer of flexibility to the task which holds more ecological validity than blocks of rewarded vs neutral trials? However, does it also demotivate the neutral trials more than a block design with neutral presented first would?
- The authors mention the possibility of age differences in assumed monetary value and thus motivational incentives. This seems like a great point. Money may be worth less to children than adolescents and perhaps worth less to adults as well. Would modulation of monetary amounts between age groups be a valid way to address this? We should also be considering socioeconomic influences on the value of money. I think additional measures should be included to explain the choice of motivation (type and strength) with the target population groups.
- The authors attempt to broaden the application of their paper by linking increased reward sensitivity during adolescence to increased risk-taking behaviors. While I do not necessarily disagree with this perspective, I think there is much more work to be done to characterize the different types and contexts of motivational mechanisms on adolescent behavior (social reward, monetary reward, sensation seeking, etc).