Wascher E, Verleger R, Vieregge P, Jaskowski P, Koch S, Kömpf D
Department of Neurology, Medical University of Lübeck, Germany.
Brain. 1997 Aug;120 ( Pt 8):1355-75. doi: 10.1093/brain/120.8.1355.
Impairment of movement execution in Parkinson's disease could be due to disorders of cognition and/or of activation. These two factors are hard to separate by measuring response times only. Therefore, in this study response force and event-related EEG potentials were measured continuously during tasks in which subjects had to respond to cued signals. Fifteen patients with Parkinson's disease and 15 healthy subjects were studied during two tasks: (i) the 'clock task', in which the signal's identity was fully precued but its presentation time was uncertain and (ii) the 'validity task' in which the cue did not always predict the response validly. Thus, the clock task required more sustained attention, and the validity task sometimes required fast switching. The patients generally responded slower than control subjects. In the clock task, the response times of both groups changed to the same extent with presentation time, whereas in the validity task the patients were additionally slower than the control group with invalidly cued signals. The patients generally had a weaker response force and a lower rate of force production. In the clock task, both force measures changed with presentation time in the control group only, whereas in the validity task, the two measures increased in both groups to the same extent with invalidly cued signals. The contingent negative variation amplitudes in the patients' event-related EEG potentials were reduced, reflecting reduced activation of movement preparation, whereas lateralization of the motor cortices (i.e. the lateralized readiness potential) did not differ significantly between groups, reflecting unimpaired response selection. Force and contingent negative variation were generally reduced in the patients showing that their general slowing is at least partially due to impaired activation. Task-specific problems added to the general activation deficit; the lack of modulation of response force by presentation time revealed pronounced deficits of activation in the monotonous clock task. The specific delay of responses with invalidly cued signals, unparalleled by activation measures, might suggest a problem of cognition. The task-specific deficits may reflect a basic dilemma for patients with Parkinson's disease: cognitive problems may arise in complex tasks but disorders of activation may become pronounced in more simple, monotonous tasks.
帕金森病中运动执行受损可能归因于认知障碍和/或激活障碍。仅通过测量反应时间很难将这两个因素区分开来。因此，在本研究中，在受试者必须对提示信号做出反应的任务过程中，持续测量了反应力和事件相关脑电图电位。对15名帕金森病患者和15名健康受试者进行了两项任务的研究：（i）“时钟任务”，其中信号的特征完全预先提示，但呈现时间不确定；（ii）“有效性任务”，其中提示并不总是能有效预测反应。因此，时钟任务需要更多持续注意力，而有效性任务有时需要快速切换。患者的反应通常比对照组慢。在时钟任务中，两组的反应时间随呈现时间的变化程度相同，而在有效性任务中，对于无效提示信号，患者比对照组更慢。患者的反应力通常较弱，力产生率较低。在时钟任务中，仅对照组的两种力测量指标随呈现时间变化，而在有效性任务中，对于无效提示信号，两组的这两种测量指标增加程度相同。患者事件相关脑电图电位中的伴随负变化幅度减小，反映运动准备激活减少，而运动皮层的侧化（即侧化准备电位）在两组之间无显著差异，反映反应选择未受损。患者的力和伴随负变化通常降低，表明他们的总体反应迟缓至少部分是由于激活受损。特定任务问题加重了总体激活缺陷；在单调的时钟任务中，呈现时间对反应力缺乏调节表明存在明显的激活缺陷。对于无效提示信号的反应出现特定延迟，而激活测量指标未出现相应变化，这可能暗示存在认知问题。特定任务缺陷可能反映了帕金森病患者面临的一个基本困境：复杂任务中可能出现认知问题，但在更简单、单调的任务中激活障碍可能更为明显。
