Executive Functions and Motor Adaptation to Predictable and Unpredictable Perturbations

In this study, we aimed to investigate the influence of executive functions (EF) on motor adaptation. We compared the motor performance of adults with and without EF deficits. Those with EF deficits (n = 21) were individuals with attention deficit hyperactivity disorder (ADHD) under medical treatment, and those without EF deficits (n = 21) comprised a control group (CG) of participants who were also without neurological or psychiatric diagnoses. Both groups performed a complex coincident timing motor task and various computerized neuropsychological tests for assessing EF. To investigate motor adaptation, the motor task provided measures of absolute error (AE) and variable error (VE) to reflect, respectively, performance accuracy and consistency relative to the task goal. We used reaction time (RT) to measure planning time taken before starting the task. First, participants practiced until they reached a criterion of performance stabilization (prior to their exposure to motor perturbations). They were next exposed to fast and slow predictable and unpredictable perturbations. On all neuropsychological tasks, participants with ADHD scored more poorly than control participants (p < .05); participants with ADHD also performed worse than control participants on all motor measures, particularly under unpredictable perturbations (p < .05). Under slow perturbations, EF deficits, particularly attentional impulsivity, negatively affected motor adaptation while cognitive flexibility was related to performance improvement. Under fast perturbations, both impulsivity and fast reaction time were related to improvement in motor adaptation under both predictable and unpredictable perturbations. We discuss the research and practical implications of these findings.