Task-Switch Related Reductions in Neural Distinctiveness in Children and Adults: Commonalities and Differences

Goal-directed behavior requires the ability to flexibly switch between task sets with changing environmental demands. Switching between tasks generally comes at the cost of slower and less accurate responses. Compared to adults, children often show greater switch costs, presumably reflecting the protracted development of the ability to flexibly update task-set representations. To test whether the distinctiveness of neural task-set representations is more strongly affected by a task switch in children compared to adults, we examined multi-voxel patterns of fMRI activation in 88 children (8–11 years, 49 girls, 39 boys) and 52 adults (20–30 years, 27 women, 25 men) during a task-switching paradigm. Using multivariate pattern analysis (MVPA), we investigated whether task-set representations were less distinct on switch than on repeat trials across frontoparietal, cingulo-opercular, and temporo-occipital regions. Children and adults showed lower accuracy and longer response times on switch than on repeat trials. Switch costs were similar across groups. Decoding accuracy was lower on switch than repeat trials, suggesting that switching reduces the distinctiveness of task-set representations. Reliable age differences in switch-related reductions of decoding accuracy were absent. More nuanced analyses using probability measures indicated that the distinctiveness of task sets was more affected by switch demand in children than in adults in a subset of frontal, cingulate and temporal regions. These results point to a remarkable degree of maturity of neural representations of task-relevant information in late childhood along with more subtle region-specific age differences in the effects of task switching on rule representation. Significance statement The ability to flexibly switch between tasks enables goal-directed behavior, but is particularly challenging for children, potentially due to protracted development in the ability to represent multiple and overlapping task rules that link stimuli to appropriate responses. We tested this hypothesis using functional MRI to measure brain activity during task switching in 8–11-year-olds and adults. Activation patterns in frontal, parietal, and temporal regions indicated with above-chance accuracy which task a person was performing when the task remained the same, but not when it had switched. Children showed larger differences in a subset of frontal and temporal regions when tasks switched, suggesting more subtle age differences in the contributions of developing rule representations to flexible behavior.