To examine individual differences in cognitive behavioural self-regulation early in development, neural activity during a probabilistic learning task were correlated to measures of impulsivity in 8 normally developing children (10-12 years of age). Children completed a probabilistic learning task in an fMRI scanner and a delay discounting task, used to measure impulsivity, outside the scanner. Choices on the delay discounting task were modeled using a quasi-hyperbolic function, representing participant’s subjective interpretation of a reward as a function of the delay period in which they must wait to obtain the reward. Subsequently, ventral striatum BOLD activity was correlated to individual performance during the probabilistic learning task, as well as to the quasi-hyperbolic model of the participant’s delay discounting curve. It was hypothesized that the magnitude of ventral striatal activity would positively correlate to parameters of individual delay discounting functions. More impulsive individuals, denoted by steeper delay discounting functions, were expected to have more BOLD activity in the ventral striatum during the probabilistic learning task than those with a more modest delay discounting function, or who are less impulsive. Contrary to these predictions, ventral striatal activity was found to be negatively correlated to the quasi-hyperbolic function, modeling a developmental switch of cognitive processing in regard to self-regulation. The present results with regard to ventral striatal activity, have the potential to serve as a biomarker of individual differences in cognitive behavioural self-regulation in normally developing children.
Available at: http://works.bepress.com/jbruce-morton/1/