Dopamine and Motor Learning in Cerebral Palsy

Objective The broad objective of this study is to determine the relationship between variations in genes related to dopamine (DA) neurotransmission in areas of the brain associated with motor leaning (e.g. DRD1, DRD2, DRD3, COMT, DAT) and/or to activity-dependent brain plasticity (e.g. BDNF) and differences in motor learning rates and cognitive processing abilities in persons with and without cerebral palsy (CP). We hypothesize that individual genetic differences will be related to the ability to learn new motor and cognitive skills and may thus provide a potential explanation for the often reported response variability to rehabilitative therapies seen in CP. We will also explore whether motor and cognitive learning abilities are correlated within individuals which could suggest similar underlying neural mechanisms. Finally we would like to evaluate the effect of rewards on procedural learning in those with and without CP, to preliminarily assess how behavioral manipulations of the DA system may affect learning. Study Population: A maximum of 120 ambulatory children and young adults with and without CP (ages 5-25 inclusive) will be enrolled in this protocol. Design: This protocol will consist of two separate but related studies: Study #1 is an observational trial whereby subjects with and without CP will participate in two different training paradigms, 10 sessions each, one that involves learning novel working memory tasks and one that involves motor skill learning in the lower extremities, adapted from the horizontal ladder task utilized in rodent studies. All will have blood draws for genetic analyses at baseline, the results of which will be related to changes in performance (learning) per task after training. Study #2 will be a within-subjects evaluation in CP and controls on the effects of reward (versus no-reward) during learning, which is presumed to increase dopamine transmission. Mean and individual responses to reward-based learning will be assessed and related to genetic variations in dopamine transmission. For subjects with CP, we would like to obtain brain MRI but this is optional and if they are unable or unwilling to do this portion, they can still participate in this protocol. Outcome Measures: Primary outcomes are changes in performance (learning) on each task after training which will be related to presence or absence of polymorphisms that have been associated with brain plasticity or with deficits in working memory and/or motor learning. Individual responses to rewards will also be related to variations related to high versus low dopamine transmission in the brain.