Abstract
Studies of the mesocorticolimbic reward system (MCLS) and its relationship with impulsivity and substance use disorders (SUD) have largely focused on individuals from non-minority backgrounds. This represents a significant gap in the literature particularly for minority populations who are disproportionately affected by the consequences of SUD. Using resting-state functional MRI (fMRI), we examined the coherence of neural activity, or functional connectivity, within the brain’s MCLS in 28 young adult Puerto Ricans (ages 25–27) who were part of a population-based cohort study. Half of the sample lived in San Juan, Puerto Rico; the other half lived in the South Bronx, New York. At each of the two sites, half of the sample had a history of a SUD. Relative to those without SUD, individuals with SUD had decreased connectivity between the nucleus accumbens (NAcc) and several regions within the MCLS. This finding was true irrespective of study site (i.e., San Juan or South Bronx). Reduced connectivity within the MCLS was also associated with higher self-reported levels of impulsivity. Path analysis suggested a potential mechanism linking impulsivity, the MCLS, and SUD: impulsivity, potentially by chronically promoting reward seeking behaviors, may contribute to decreased MCLS connectivity, which in turn, may confer vulnerability for SUD. Expanding upon prior studies suggesting that alterations within the MCLS underlie SUD, our findings suggest that such alterations are also related to impulsivity and are present in a high-risk young minority population.
Highlights
MRI studies suggest that substance use disorders (SUD) and impulsivity are both associated with atypical neural connections within the brain’s mesocorticolimbic reward system (MCLS; Gu et al, 2010; Tomasi et al, 2010; Upadhyay et al, 2010), which includes the midbrain’s ventral tegmental area (VTA), the nucleus accumbens (NAcc), and the orbitofrontal cortex (OFC).Mesocorticolimbic Connectivity in SUDthe inter-relationships between the MCLS, impulsivity, and SUD remain poorly characterized.Substance use is associated with increased extracellular dopamine (DA) within the MCLS (Volkow et al, 2007)
We found that reduced connectivity between specific MCLS regions was associated with higher levels of impulsivity
Path analysis offered initial support for a mechanistic account of these findings: impulsivity may contribute to decreased MCLS connectivity, which in turn, may confer vulnerability for developing SUD
Summary
MRI studies suggest that substance use disorders (SUD) and impulsivity are both associated with atypical neural connections within the brain’s mesocorticolimbic reward system (MCLS; Gu et al, 2010; Tomasi et al, 2010; Upadhyay et al, 2010), which includes the midbrain’s ventral tegmental area (VTA), the nucleus accumbens (NAcc), and the orbitofrontal cortex (OFC). MCLS connectivity in Puerto Rican individuals with SUD has not been studied and it has scarcely been examined in Latinos in general. We examined the MCLS and its relationship with SUD in individuals of Puerto Rican descent by studying participants from a large, epidemiological cohort study of Puerto Ricans living in the South Bronx, New York and the metropolitan area in San Juan, Puerto Rico. Toward this end, resting fMRI scans were obtained and analyzed from 28 young adult Puerto Ricans (ages 25–27). We used path analysis to explore a potential mechanism relating impulsivity, MCLS connectivity, and SUD
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