Brain regions mediating flexible rule use during development

Abstract

During development, children improve at retrieving and using rules to guide their behavior and at flexibly switching between these rules. In this study, we used functional magnetic resonance imaging to examine the changes in brain function associated with developmental changes in flexible rule use. Three age groups (8-12, 13-17, and 18-25 years) performed a task in which they were cued to respond to target stimuli on the basis of simple task rules. Bivalent target stimuli were associated with different responses, depending on the rule, whereas univalent target stimuli were associated with fixed responses. The comparison of bivalent and univalent trials enabled the identification of regions modulated by demands on rule representation. The comparison of rule-switch and rule-repetition trials enabled the identification of regions involved in rule switching. We have used this task previously in adults and have shown that ventrolateral prefrontal cortex (VLPFC) and the (pre)-supplementary motor area (pre-SMA/SMA) have dissociable roles in task-switching, such that VLPFC is associated most closely with rule representation, and pre-SMA/SMA is associated with suppression of the previous task set (Crone et al., 2006a). Based on behavioral data in children (Crone et al., 2004), we had predicted that regions associated with task-set suppression would show mature patterns of activation earlier in development than regions associated with rule representation. Indeed, we found an adult-like pattern of activation in pre-SMA/SMA by adolescence, whereas the pattern of VLPFC activation differed among children, adolescents, and adults. These findings suggest that two components of task-switching--rule retrieval and task-set suppression--follow distinct neurodevelopmental trajectories.

Figure 1.

Display of rule types. During scanning, participants viewed an instructional cue for 1 s. After a 0.5 s delay, the target stimulus was presented for 2.5 s. The target required a left- or right-button response, depending on the relevant S–R mapping learned before scanning.

Figure 2.

Performance on the blocked and mixed tasks. RTs are shown for correct responses only. In the mixed task, RTs and accuracy are plotted separately for univalent and bivalent rules and for rule repetitions and rule switches. BLOCK, Blocked presentation; REP, repetition trials in the mixed block; SWITCH, switch trials in the mixed block. In the mixed task, participants performed worse on bivalent trials than on univalent trials and worse on switch trials than on repetition trials. These effects were largest for participants aged 8–12 years.

Figure 3.

ROI results for left (L-) VLPFC (BA 45; −42, 24, 18), left pre-SMA/SMA (BA 6; −6, 3, 60), and left superior parietal cortex (BA 7; −24, −66, 52) for children, adolescents, and adults. BLOCK, Blocked presentation; REP, repetition trials in the mixed block; SWITCH, switch trials in the mixed block. All ROIs were identified by the whole-brain contrast of all correct trials relative to fixation, across all participants (p < 0.001 uncorrected). Error bars depict an estimate of within-subject SE.

Figure 4.

Overlap in activation for children aged 8–12 years and adults for the contrast bivalent rules > univalent rules in the mixed task. Activation in children is in red; activation in adults is in yellow. The overlap between children and adults is in orange. Rule-related activation was observed for both age groups in left VLPFC (BA 44, 45), bilateral insula (BA 13), and pre-SMA/SMA (BA 6).