Is there a relation between novelty seeking, striatal dopamine release and frontal cortical thickness?

BACKGROUND: Novelty-seeking (NS) and impulsive personality traits have been proposed to reflect an interplay between fronto-cortical and limbic systems, including the limbic striatum (LS). Although neuroimaging studies have provided some evidence for this, most are comprised of small samples and many report surprisingly large effects given the challenges of trying to relate a snapshot of brain function or structure to an entity as complex as personality. The current work tested a priori hypotheses about associations between striatal dopamine (DA) release, cortical thickness (CT), and NS in a large sample of healthy adults. METHODS: Fifty-two healthy adults (45M/7F; age: 23.8±4.93) underwent two positron emission tomography scans with [(11)C]raclopride (specific for striatal DA D(2/3) receptors) with or without amphetamine (0.3 mg/kg, p.o.). Structural magnetic resonance image scans were acquired, as were Tridimensional Personality Questionnaire data. Amphetamine-induced changes in [(11)C]raclopride binding potential values (ΔBP(ND)) were examined in the limbic, sensorimotor (SMS) and associative (AST) striatum. CT measures, adjusted for whole brain volume, were extracted from the dorsolateral sensorimotor and ventromedial/limbic cortices. RESULTS: BP(ND) values were lower in the amphetamine vs. no-drug sessions, with the largest effect in the LS. When comparing low vs. high LS ΔBP(ND) groups (median split), higher NS2 (impulsiveness) scores were found in the high ΔBP(ND) group. Partial correlations (age and gender as covariates) yielded a negative relation between ASTS ΔBP(ND) and sensorimotor CT; trends for inverse associations existed between ΔBP(ND) values in other striatal regions and frontal CT. In other words, the greater the amphetamine-induced striatal DA response, the thinner the frontal cortex. CONCLUSIONS: These data expand upon previously reported associations between striatal DA release in the LS and both NS related impulsiveness and CT in the largest sample reported to date. The findings add to the plausibility of these associations while suggesting that the effects are likely weaker than has been previously proposed.