The ability to plan and understand complex actions is a crucial aspect of human cognition. It is discussed as a key milestone in early cognitive development and considerably develops around the preschool years. Processing complex action steps serve as basis for learning and goal-directed behavior. Previous research suggests that the processing of hierarchically structured actions recruit the inferior frontal cortex (IFC), which is critically involved in hierarchical processing in language (Fadiga, et al., 2009). Recent meta-analyses on action and language processing in adults suggest that different subregions of the left IFC underlie structural processing of language and action (Zaccarella, et al., 2021). However, to this date, the underlying neural mechanisms of children’s action processing are largely unknown. Here, we compare structural action processing and its neural correlates in children and adults using a stacking game while measuring fNIRS. We instructed N=78 children and N=47 adults to place six blocks varying in shape and size on to a small board to build a pathway for two toy figures. Task levels included two condition structures: sequential action sequences, in which the placing order of the blocks was flexible, and dependent action sequences, in which the blocks needed to be placed in a specific order. Participants were presented with twelve levels of increasing difficulty, six in each condition. We measured participant’s neural response using fNIRS in a 30 second planning phase, where the setup was revealed but out of reach, followed by a 60 second building phase, in which the task was solved. Participant’s behavioral performance was coded based on their success. We hypothesize that structural complexity of action sequences modulates the activation of regions in IFC, with stronger activation for hierarchically dependent than sequential sequences. If such activation indexes structural processing, we further expect correlations between task performance and neural response. Our findings in children show activation in the left frontal, posterior region, presumably corresponding to BA6, with stronger activation for order-dependent levels than sequential, flexible levels. These findings highlight the importance of BA6 in the process of planning an action sequence before executing an action. Our findings in adults show deactivation in the left and right frontal region, roughly corresponding with BA44, with less effects for sequential, flexible levels than order-dependent levels. In sum, our results show that preschool children seem to experience difficulties with organizing and structuring action sequences that rely on order-dependencies. While children seem to mainly rely on the premotor cortex for solving order-dependent levels, adults appear to recruit brain regions corresponding with BA44.
This is a CEN seminar.