Alberts J L, Saling M, Adler C H, Stelmach G E
Motor Control Laboratory, Arizona State University, Tempe 85287-0404, USA.
Exp Brain Res. 2000 Oct;134(3):353-62. doi: 10.1007/s002210000468.
Previous research has shown that Parkinson's-disease (PD) patients produce irregular movement paths during a rapid arm pointing task. The aim of this study was to investigate the movement paths of PD patients during a prehensile action to objects requiring different levels of precision. Thus, we sought to determine if movement-accuracy requirements affect the control of movement path. Thirteen PD patients and 13 age-matched controls served as participants. In addition to having prolonged movement times, PD patients showed differences in the kinematic patterns of the transport and grasp components. For the transport component, relative time to maximum deceleration and relative time to maximum elbow velocity occurred earlier for the PD patients than the controls. Analyses of wrist paths indicated that, when accuracy requirements were increased, patients produced paths that appeared more segmented than controls. For PD patients, reaches to a small object resulted in wrist paths that were significantly less smooth, as reflected by higher jerk values, and were less continuous, as indicated by larger standard deviations in curvature. A temporal analysis of movement-initiation patterns in the vertical and horizontal planes indicated that control participants had a minimal offset between initial movement in the vertical plane and initial movement in the horizontal plane regardless of accuracy constraints. However, PD patients had a significantly longer interval between initial movement in the vertical plane and subsequent movement in the horizontal plane when reaching to the small object. Higher accuracy constraints also resulted in PD patients achieving relative time to maximum elbow velocity significantly earlier than controls. For the grasp component, PD patients produced movement patterns in which the amplitude of and relative time to maximum aperture were less sensitive to object size. In addition, patients exhibited greater variability in the time to maximum aperture. Additional analyses of the grasp component indicated that control participants exhibited a stable position, relative to object location, in which aperture began to close. Conversely, PD patients showed little consistency in where aperture began to close with respect to object location. Irregularities in the transport component suggest that PD patients have a reduced capability to precisely coordinate joint segments, particularly under high accuracy requirements. Variability in where aperture began to close and disruptions in transport-grasp coordination suggests that the basal-ganglia dysfunction, as exhibited in PD, affects the specification of these movement parameters used to produce a consistent pattern of coordination between prehensile components.
先前的研究表明，帕金森病（PD）患者在快速手臂指向任务中会产生不规则的运动轨迹。本研究的目的是调查PD患者在抓取不同精度要求物体的动作过程中的运动轨迹。因此，我们试图确定运动精度要求是否会影响运动轨迹的控制。13名PD患者和13名年龄匹配的对照者作为参与者。除了运动时间延长外，PD患者在运输和抓握部分的运动学模式上也存在差异。对于运输部分，PD患者达到最大减速的相对时间和达到最大肘部速度的相对时间比对照者更早出现。对手腕轨迹的分析表明，当精度要求提高时，患者产生的轨迹比对照者显得更分段。对于PD患者，抓取小物体时导致手腕轨迹明显不那么平滑，这表现为更高的急动值，并且连续性更差，这由曲率的更大标准差表明。对垂直和水平平面上运动起始模式的时间分析表明，无论精度限制如何，对照参与者在垂直平面上的初始运动和水平平面上的初始运动之间的偏移最小。然而，当抓取小物体时，PD患者在垂直平面上的初始运动和随后在水平平面上的运动之间的间隔明显更长。更高的精度限制也导致PD患者比对照者显著更早达到最大肘部速度的相对时间。对于抓握部分，PD患者产生的运动模式中，最大孔径的幅度和相对时间对物体大小不太敏感。此外，患者在达到最大孔径的时间上表现出更大的变异性。对抓握部分的进一步分析表明，对照参与者相对于物体位置表现出一个稳定的位置，在该位置孔径开始闭合。相反，PD患者在孔径相对于物体位置开始闭合的位置上几乎没有一致性。运输部分的不规则性表明，PD患者精确协调关节节段的能力下降，特别是在高精度要求下。孔径开始闭合位置的变异性以及运输-抓握协调的中断表明，PD中表现出的基底神经节功能障碍会影响用于在抓握部分之间产生一致协调模式的这些运动参数的设定。
