Given the network level approach of using ICA we were
Given the network level approach of using ICA, we were particularly interested in examining between-functional resting-state network (RSN) connectivity between the limbic and right fronto-parietal networks (FPN). The limbic network broadly includes amygdala, VS, primary olfactory, limbic associated cortices (BA 28/34/35/36/38), orbitofrontal cortex (OFC), thalamus and basal ganglia (BG), and is involved in emotional and autonomic processes for reward, fear, and anxiety (Janes et al., 2012; Laird et al., 2011; Yeo et al., 2011), indicating that this network represents the p53 tumor suppressor system for bottom-up emotional processing. The right FPN composes of dlPFC, inferior parietal lobule (IPL), intraparietal sulcus (IPS) and midcingulate on the right side of brain and is well known for its strong involvement in multiple top-down cognitive control processes that require continuous attentional monitoring, response inhibition, and control (Barrós-Loscertales et al., 2011; Corbetta et al., 2008; Dosenbach et al., 2008; Dosenbach et al., 2007; Fair et al., 2009, 2007; Garavan et al., 2008; Vincent et al., 2008; Weissman et al., 2015). Although the FPN exists bilaterally, the left FPN is recruited for higher level language processing such as comprehension, reading, and explicit working memory with a dominance of semantic and phonologic information (Laird et al., 2011), and therefore we focused on the right FPN in the current study.
In sum, the goal of the present study was to provide a between-network level examination of adolescents’ brain connectivity and links to self-control and substance use onset. We predicted that adolescents who show more inverse functional coupling between the right FPN and limbic network (LN) would show higher self-control which would contribute to later substance use onset (e.g., Weissman et al., 2015). The transition to mid adolescence (e.g., 13–17 years) is a developmental period marked by steep increases in risky behavior and poor self-control. For instance, lifetime illicit drug use more than doubles and current drug use (i.e., use within the past 30days) more than triples between ages 13 and 17, such that by age 17 nearly half of youth have tried a drug at least once (Johnson et al., 2009). Therefore, in the current study, we focused on mid adolescents ranging from 13 to 17 years.
Results Our primary goal was to examine how the right frontoparietal-limbic connectivity is related to self-control and substance-use-onset in adolescents. To this end, we first examined relationships between these variables (i.e., network connectivity, self-control, and substance-use-onset). To reduce possible impact of non-normal, skewed distribution of our substance use measure, we employed a robust method (Pernet et al., 2012) combined with bootstrapping resampling (n=5000).
Discussion The goal of the present study was to examine the neural correlates underlying adolescents’ substance use and self-control by focusing on two resting-state intrinsic networks, the right FPN and limbic network. We successfully replicated and extended previous findings regarding resting state connectivity patterns and substance-use behavior in adolescents (Weissman et al., 2015) by demonstrating that more negatively coupled right frontoparietal-limbic connectivity is associated with higher self-control ability and later substance use onset in adolescence. Our findings support the idea that negative functional coupling between the top-down frontal system and bottom-up limbic system could be an index of developmental brain maturation during adolescence. Importantly, the current study provides evidence for the relationship between top-down control enhancement and suppression of bottom-up activity in adolescent risky behavior at the “between-network level” by adopting an ICA approach. Together, the current study increases our understanding of adolescent neural network connectivity and its relation to self-control and substance use behavior.