Psychology Department, Rutgers University, Piscataway, New Jersey 08854, USA.
J Neurosci. 2011 Dec 7;31(49):17848-63. doi: 10.1523/JNEUROSCI.1150-11.2011.
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.
外源性目标引发的预期运动往往与内源性激活的自发性、自动化运动共存。有人提出，帕金森病（PD）主要损害自动化运动，但尚不清楚这在多大程度上可能影响多关节/肢体控制，特别是当患者停止使用多巴胺能药物时。在这里，我们在患者停止使用多巴胺能药物时测试了九名 PD 患者和九名年龄匹配的正常对照组（NC）。参与者进行了有意的向前伸展动作，以达到黑暗房间中的目标，然后返回到初始姿势。在目标闪烁时，使用了三种形式的指导：（1）闭眼时的记忆，（2）仅连续目标视觉，（3）仅移动手指的视觉。测量了他们手臂关节的轨迹，并将其关节速度分解为（预期的）任务相关和（自发的）任务偶然自由度（DOF）。我们还测量了这两个自由度子集在这些运动展开过程中的平衡。在 PD 患者中，我们发现回缩运动期间偶然自由度值异常可变，并超过任务相关自由度值。相比之下，他们的向前意向运动异常受任务相关组件支配。此外，患者在自愿和自动化关节控制模式之间突然转换，与 NC 不同，视觉指导的类型对其姿势轨迹有不同的影响。这些发现支持了一种新兴观点，即 PD 患者存在自动化控制丧失，这导致自愿控制受损，基底节-皮层回路对于多关节控制的维持和平衡至关重要。
