Action Observation Network Activity Related to Object- Directed and Socially-Directed Actions in Adolescents

The human action observation network (AON) encompasses brain areas consistently engaged when we observe other's actions. Although the core nodes of the AON are present from childhood, it is not known to what extent they are sensitive to different action features during development. Because social cognitive abilities continue to mature during adolescence, the AON response to socially-oriented actions, but not to object-related actions, may differ in adolescents and adults. To test this hypothesis, we scanned with functional magnetic resonance imaging (fMRI) male and female typically-developing teenagers (n = 28; 13 females) and adults (n = 25; 14 females) while they passively watched videos of manual actions varying along two dimensions: sociality (i.e., directed toward another person or not) and transitivity (i.e., involving an object or not). We found that action observation recruited the same fronto-parietal and occipito-temporal regions in adults and adolescents. The mod-ulation of voxel-wise activity according to the social or transitive nature of the action was similar in both groups of partici-pants. Multivariate pattern analysis, however, revealed that decoding accuracies in intraparietal sulcus (IPS)/superior parietal lobe (SPL) for both sociality and transitivity were lower for adolescents compared with adults. In addition, in the lateral occi-pital temporal cortex (LOTC), generalization of decoding across the orthogonal dimension was lower for sociality only in ado-lescents. These findings indicate that the representation of the content of others' actions, and in particular their social dimension, in the adolescent AON is still not as robust as in adults.

Automated summary

The human action observation network (AON) is engaged when observing other's actions, and it is not known to what extent it is sensitive to different action features during development. In this study, both adolescents and adults were scanned using fMRI while watching videos of actions varying in sociality and transitivity. The results showed that the AON responded similarly in both groups, but adolescents had lower decoding accuracies for sociality and transitivity in certain brain regions. These findings suggest that the adolescent AON is not as robust in representing the social dimension of others' actions as in adults.