Hodgson T L, Dittrich W H, Henderson L, Kennard C
Department of Sensorimotor Systems, Imperial College School of Medicine, Charing Cross Hospital, London, UK.
Neuropsychologia. 1999 Jul;37(8):927-38. doi: 10.1016/s0028-3932(98)00151-1.
Mechanisms of spatial working memory and eye movement control were investigated in eight mild to moderate Parkinson's disease patients (PDs). Subjects were presented with a sequence of four targets which had to be memorized and then recalled by moving their eyes to fixate the four locations in the correct order. Two variations on this procedure were used in which either a different sequence of lights was presented on each trial, or an identical sequence of lights was repeated on each trial. In both conditions subjects made memory-guided eye movements in the dark, without any visual cues to eye movement accuracy or the locations of the previously illuminated lights. Analysis of the amplitude of the primary eye movement and final eye position for each step in the sequence showed that PDs made several discrete saccadic eye movements of reduced amplitude before reaching the final eye position (multi-stepping). When a novel target sequence had to be memorized on each trial, the final eye position reached by PDs for each location was also found to undershoot relative to controls. In contrast, when an identical sequence of targets was repeated on each trial, PDs' final eye position was found to be normal, although primary movement amplitudes were still reduced. PDs showed no multi-stepping and normal final eye position gain under conditions for which the target lights in the sequence were illuminated during movement execution. PDs also made an increased proportion of overt errors in target sequence recall. Parallel neuropsychological testing in PDs and controls revealed that error rates in the sequential memory-guided saccade task were significantly correlated with performance in a task thought to be sensitive to spatial working memory dysfunction. The findings suggest that short-term spatial memory representations are disrupted in the early stages of PD.
对八名轻度至中度帕金森病患者（PD患者）的空间工作记忆和眼球运动控制机制进行了研究。向受试者呈现四个目标的序列，他们必须记住这些目标，然后通过按正确顺序移动眼睛注视这四个位置来进行回忆。使用了该程序的两种变体，一种是每次试验呈现不同的灯光序列，另一种是每次试验重复相同的灯光序列。在这两种情况下，受试者都在黑暗中进行记忆引导的眼球运动，没有任何视觉线索来提示眼球运动的准确性或先前照亮的灯光的位置。对序列中每一步的主要眼球运动幅度和最终眼球位置的分析表明，PD患者在到达最终眼球位置之前会进行几次幅度减小的离散扫视眼球运动（多步运动）。当每次试验都必须记住一个新的目标序列时，还发现PD患者在每个位置到达的最终眼球位置相对于对照组会出现 undershoot（未达目标位置）。相比之下，当每次试验重复相同的目标序列时，发现PD患者的最终眼球位置正常，尽管主要运动幅度仍然减小。在运动执行过程中序列中的目标灯光被照亮的条件下，PD患者没有出现多步运动，并且最终眼球位置增益正常。PD患者在目标序列回忆中明显错误的比例也增加。对PD患者和对照组进行的平行神经心理学测试表明，在连续记忆引导扫视任务中的错误率与一项被认为对空间工作记忆功能障碍敏感的任务中的表现显著相关。研究结果表明，在帕金森病的早期阶段，短期空间记忆表征受到了破坏。 （注：“undershoot”这个词在医学语境下较难准确翻译，这里直接保留英文，以免影响对整体内容的理解。如有更准确的专业术语可替换。）
