Department of Robotics, Brain and Cognitive Sciences, Italian Institute of Technology, Genova 16163, Italy.
Brain. 2012 Nov;135(Pt 11):3371-9. doi: 10.1093/brain/aws265.
This study investigated how Parkinson's disease alters haptic perception and the underlying mechanisms of somatosensory and sensorimotor integration. Changes in haptic sensitivity and acuity (the abilities to detect and to discriminate between haptic stimuli) due to Parkinson's disease were systematically quantified and contrasted to the performance of healthy older and young adults. Using a robotic force environment, virtual contours of various curvatures were presented. Participants explored these contours with their hands and indicated verbally whether they could detect or discriminate between two contours. To understand what aspects of sensory or sensorimotor integration are altered by ageing and disease, we manipulated the sensorimotor aspect of the task: the robot either guided the hand along the contour or the participant actively moved the hand. Active exploration relies on multimodal sensory and sensorimotor integration, while passive guidance only requires sensory integration of proprioceptive and tactile information. The main findings of the study are as follows: first, a decline in haptic precision can already be observed in adults before the age of 70 years. Parkinson's disease may lead to an additional decrease in haptic sensitivity well beyond the levels typically seen in middle-aged and older adults. Second, the haptic deficit in Parkinson's disease is general in nature. It becomes manifest as a decrease in sensitivity and acuity (i.e. a smaller perceivable range and a diminished ability to discriminate between two perceivable haptic stimuli). Third, thresholds during both active and passive exploration are elevated, but not significantly different from each other. That is, active exploration did not enhance the haptic deficit when compared to passive hand motion. This implies that Parkinson's disease affects early stages of somatosensory integration that ultimately have an impact on processes of sensorimotor integration. Our results suggest that the known motor problems in Parkinson's disease that are generally characterized as a failure of sensorimotor integration may, in fact, have a sensory origin.
本研究调查了帕金森病如何改变触觉感知以及体感和感觉运动整合的潜在机制。帕金森病导致的触觉灵敏度和锐度（检测和区分触觉刺激的能力）变化被系统地量化，并与健康的老年和年轻成年人的表现进行了对比。使用机器人力环境，呈现了各种曲率的虚拟轮廓。参与者用手探索这些轮廓，并口头表示他们是否能够检测或区分两个轮廓。为了了解衰老和疾病如何改变感觉或感觉运动整合的哪些方面，我们操纵了任务的感觉运动方面：机器人要么引导手沿着轮廓移动，要么让参与者主动移动手。主动探索依赖于多模态感觉和感觉运动整合，而被动引导只需要本体感觉和触觉信息的感觉整合。该研究的主要发现如下：首先，在 70 岁之前，成年人的触觉精度就已经开始下降。帕金森病可能导致触觉灵敏度进一步下降，远远超出中年和老年成年人的典型水平。其次，帕金森病的触觉缺陷具有普遍性。它表现为灵敏度和锐度下降（即感知范围缩小，区分两个可感知触觉刺激的能力降低）。第三，主动和被动探索时的阈值都升高了，但彼此之间没有显著差异。也就是说，与被动手部运动相比，主动探索并没有增强触觉缺陷。这意味着帕金森病影响体感整合的早期阶段，最终影响感觉运动整合过程。我们的研究结果表明，帕金森病中已知的运动问题通常被认为是感觉运动整合失败的原因，实际上可能具有感觉起源。
