Neural similarity in nucleus accumbens during decision-making for the self and a best friend: Links to adolescents' self-reported susceptibility to peer influence and risk taking

Abstract

Adolescence is marked by increased peer influence on risk taking; however, recent literature suggests enormous individual variation in peer influence susceptibility to risk-taking behaviors. The current study uses representation similarity analysis to test whether neural similarity between decision-making for self and peers (i.e., best friends) in a risky context is associated with individual differences in self-reported peer influence susceptibility and risky behaviors in adolescents. Adolescent participants (N = 166, M_age = 12.89) completed a neuroimaging task in which they made risky decisions to receive rewards for themselves, their best friend, and their parents. Adolescent participants self-reported peer influence susceptibility and engagement in risk-taking behaviors. We found that adolescents with greater similarity in nucleus accumbens (NACC) response patterns between the self and their best friend reported greater susceptibility to peer influence and increased risk-taking behaviors. However, neural similarity in ventromedial prefrontal cortex (vmPFC) was not significantly associated with adolescents' peer influence susceptibility and risk-taking behaviors. Further, when examining neural similarity between adolescents' self and their parent in the NACC and vmPFC, we did not find links to peer influence susceptibility and risk-taking behaviors. Together, our results suggest that greater similarity for self and friend in the NACC is associated with individual differences in adolescents' peer influence susceptibility and risk-taking behaviors.

Keywords: adolescent; individual difference; peer influence; representational similarity analysis (RSA); risk taking.

FIGURE 1

Example trial of the modified cups task during scan. In this example, participants chose the risky option and subsequently gained a reward of cents. Each trial consists of an intertrial jittered fixation, a decision‐making phase in which adolescents will make a response (risky or safe), an outcome jittered fixation, and an outcome phase in which adolescents will see the outcome of their decisions.

FIGURE 2

Regions of interest used for representational similarity analyses. NACC, nucleus accumbens; vmPFC, ventromedial prefrontal cortex. The NACC and vmPFC were meta‐analytically defined using NeuroSynth (https://neurosynth.org/). Meta‐analysis results were corrected using false discovery rate (FDR; p < .01). Peak coordinates for regions of interest were selected. All selected regions of interest (ROIs) were displayed using FSLeyes.

FIGURE 3

Schematic of representational similarity analysis procedure. (a) The voxel‐wise similarity matrices of decision‐making for adolescents' selves and their best friends, respectively. Predefined right nucleus accumbens (NACC) in one subject was shown as an example here. (b) We conducted a pairwise correlation between the neural responses for the neural similarity for each subject in each region of interest (ROI). Note that this figure is only for illustration purpose (not actual heat maps), each cell in the matrices represents a trial‐based parameter estimate (i.e., beta weight) at voxel level.

FIGURE 4

Distribution of the coefficients for the similarity between decision‐making for the self and best friend. lNACC and rNACC—left and right nucleus accumbens. Error bars represent the standard deviations (SD). As the figure shows, there is individual variation in the way adolescents similarly represent the self and their best friend while making decisions in risk‐taking contexts.

FIGURE 5

Regressions of susceptibility to peer influence and risk taking on the neural similarity in the nucleus accumbens (NACC). Neural similarity in the NACC between decision‐making for the self and a best friend is positively associated with adolescents' (a) Susceptibility to peer influence and (b) risk‐taking behavior. Neural similarity in the NACC between decision‐making for the self and a parent is not significantly associated with adolescents' (c) Susceptibility to peer influence susceptibility or (d) risk‐taking behavior. 95% confidence intervals (CIs) for the relations are displayed. All reported p values were Bonferroni adjusted.