Adolescent development of the neural circuitry for thinking about intentions

Abstract

In this fMRI study, we investigated the development during adolescence of the neural network underlying thinking about intentions. A total of 19 adolescent participants (aged 12.1-18.1 years), and 11 adults (aged 22.4-37.8 years), were scanned using fMRI. A factorial design was employed with between-subjects factor age group and within-subjects factor causality (intentional or physical). In both adults and adolescents, answering questions about intentional causality vs physical causality activated the medial prefrontal cortex (PFC), superior temporal sulcus (STS), temporal poles and precuneus bordering with posterior cingulate cortex. In addition, there was a significant interaction between group and task in the medial PFC. During intentional relative to physical causality, adolescents activated part of the medial PFC more than did adults and adults activated part of the right STS more than did adolescents. These results suggest that the neural strategy for thinking about intentions changes between adolescence and adulthood. Although the same neural network is active, the relative roles of the different areas change, with activity moving from anterior (medial prefrontal) regions to posterior (temporal) regions with age.

Fig. 1

Behavioural results. Mean (±s.d.) reaction times in ms in the two conditions for adult and adolescent groups: IC, intentional causality; PC, physical causality. **P < 0.0001.

Fig. 2

Main effect of all conditions relative to baseline for both groups. Sagittal and coronal views through a glass brain showing average group activations in the two experimental conditions (IC and PC) compared with the baseline condition, depicting activations in parietal cortex, temporal cortex, occipital cortex and fusiform gyrus for both adults (left panel) and adolescents (right panel).

Fig. 3

Main effect of IC-PC in both groups. Sagittal and coronal views through a glass brain showing activation in medial PFC, precuneus/posterior cingulate cortex, STS, TPJ and temporal pole in the intentional causality condition vs the physical causality condition in the adult group (left panel) and the adolescent group (right panel). Anatomical labels: 1. Precuneus/posterior cingulate cortex; 2. STS/TPJ; 3. Temporal pole; 4. Medial PFC. It can be seen that the network of activation in IC-PC is similar in both groups.

Fig. 4

Medial PFC activity in both groups. Activity in medial PFC from the contrast IC–PC projected from both groups (adults in yellow; adolescents in red) superimposed on an axial slice of a T1-weighted image (right panel). Parameter estimates show relative percentage BOLD signal in voxel of maximum intensity in medial PFC in IC and PC relative to fixation baseline for adolescent group (upper left) and adult group (lower left). Note that parameter estimates are negative because activity in the fixation baseline condition has been subtracted from activity in each experimental condition.

Fig. 5

Interaction between group (adolescents vs adults) and condition (IC vs PC). Upper panel: Activity in medial PFC (12 42 21; BA 10) resulting from the contrast [(adolescentIC–adolescentPC)–(adultIC–adultPC)], projected on a sagittal slice of a T1-weighted image. Parameter estimates (right panel) show relative percentage BOLD signal in voxel of maximum intensity in medial PFC in IC and PC (relative to baseline) for both groups. Note that parameter estimates are negative because activity in the fixation baseline condition has been subtracted from activity in each experimental condition. Lower panel: Significant negative correlation between BOLD signal in medial PFC (15 45 18) in IC–PC and age (r = −0.45; P < 0.05).

Fig. 6

Interaction between group (adults vs adolescents) and condition (IC vs PC). Activity in STS (63 −33 −9) resulting from the contrast [(adultIC–adultPC)–(adolescentIC–adolescentPC)], projected on a sagittal slice of a T1-weighted image. Parameter estimates (right panel) show relative percentage BOLD signal in voxel of maximum intensity in STS in IC and PC (relative to baseline) for both groups. Note that parameter estimates are negative because activity in the fixation baseline condition has been subtracted from activity in each experimental condition.