RT Journal Article
SR Electronic
T1 Impaired Endogenously Evoked Automated Reaching in Parkinson's Disease
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 17848
OP 17863
DO 10.1523/JNEUROSCI.1150-11.2011
VO 31
IS 49
A1 Elizabeth B. Torres
A1 Kenneth M. Heilman
A1 Howard Poizner
YR 2011
UL http://www.jneurosci.org/content/31/49/17848.abstract
AB Intended reaches triggered by exogenous targets often coexist with spontaneous, automated movements that are endogenously activated. It has been posited that Parkinson's disease (PD) primarily impairs automated movements, but it is unknown to what extent this may affect multijoint/limb control, particularly when patients are off their dopaminergic medications. Here we tested nine human patients with PD while off dopaminergic medication versus nine age-matched normal controls (NCs). Participants performed intentional reaches forward to a target in a dark room and then transitioned back to their initial posture. Upon target flash, three forms of guidance were used: (1) memory with eyes closed, (2) continuous target vision only, and (3) vision of their moving finger only. The trajectories of their arm joints were measured and their joint velocities decomposed into the (intended) task-relevant and the (spontaneous) task-incidental degrees of freedom (DOF). We also measured the balance between these two subsets of DOF as these movements unfolded. In PD patients we found that the incidental DOF values were abnormally variable during the retracting movements and prevailed over the task-relevant DOF values. By contrast, their forward intentional motions were abnormally dominated by the task-relevant components. Moreover, the patients abruptly transitioned between voluntary and automated modes of joint control, and, unlike NCs, the type of visual guidance differentially affected their postural trajectories. These findings lend support to an emerging view that there is a loss of automated control in PD patients that contributes to impairments in voluntary control, and that basal ganglia–cortical circuits are critical for the maintenance and balance of multijoint control.