Beppu H, Nagaoka M, Tanaka R
Brain. 1987 Feb;110 ( Pt 1):1-18. doi: 10.1093/brain/110.1.1.
In visually-guided slow ramp elbow tracking, patients with cerebellar ataxia show irregular undulations of pursuit velocity which result in a position tracking pattern unlike the smooth constant velocity or rate tracking pattern of normal controls (Beppu et al., 1984). This task provides ample opportunity to use both visual and proprioceptive feedback information for correcting errors. The present study investigated the role of visual information for generation of this saccadic pursuit pattern in the patients. A television screen was divided into upper and lower halves in each of which a vertical strip was displayed. The upper strip (T, target) was moved horizontally from the centre of the screen to the left or right by ramp voltage. The lower strip (D, displacement of the handle) was moved in proportion to angular displacement of the handle by a potentiometer coupled to the handle axis. The subject, while sitting in front of the screen, had to make D match the movement of T by controlling the handle with his arm. The range of T movement was 30 deg in terms of the angular movement of the handle. T velocity was 6.0 or 7.5 deg/s. After a training session, the test was performed in which D or T was suddenly erased from the screen during pursuit, depriving the subject of visual information about the moving limb and/or performance. The procedure gave only minor effects on the performance of the control subjects, but it reduced significantly the velocity undulation of the patients with cerebellar ataxia, producing a smoother continuous pursuit. There were no significant differences in performance between D or T erase tasks. The result supports the hypothesis that the marked undulation pattern during pursuit movement in cerebellar ataxia is due to repeated visually-guided error correction responses. The relative importance of the visual pathway for conveying position information and the proprioceptive pathway for movement velocity information in this visual slow ramp tracking task is also discussed.
在视觉引导的慢斜坡肘部跟踪中，小脑共济失调患者的追踪速度会出现不规则波动，导致其位置跟踪模式不同于正常对照组的平滑匀速或速率跟踪模式（Beppu等人，1984年）。该任务提供了大量机会来利用视觉和本体感觉反馈信息来纠正错误。本研究调查了视觉信息在这些患者中产生这种扫视追踪模式的作用。电视屏幕被分成上下两半，每半部分都显示一条垂直条带。上条带（T，目标）通过斜坡电压从屏幕中心水平向左或向右移动。下条带（D，手柄位移）通过与手柄轴相连的电位计与手柄的角位移成比例地移动。受试者坐在屏幕前，必须通过用手臂控制手柄使D与T的移动相匹配。就手柄的角移动而言，T的移动范围为30度。T的速度为6.0或7.5度/秒。经过一次训练后，进行测试，即在追踪过程中突然从屏幕上擦除D或T，使受试者无法获得有关移动肢体和/或表现的视觉信息。该程序对对照组受试者的表现影响很小，但它显著降低了小脑共济失调患者的速度波动，产生了更平滑的连续追踪。D或T擦除任务之间的表现没有显著差异。结果支持了这样的假设，即小脑共济失调患者在追踪运动过程中明显的波动模式是由于反复的视觉引导错误纠正反应。本文还讨论了在这个视觉慢斜坡跟踪任务中，视觉通路在传递位置信息方面的相对重要性以及本体感觉通路在传递运动速度信息方面的相对重要性。
