Donders Institute for Brain, Cognition and Behaviour, Centre for Cognitive Neuroimaging, Radboud University Nijmegen, the Netherlands.
Hum Brain Mapp. 2012 Aug;33(8):1763-79. doi: 10.1002/hbm.21318. Epub 2011 Jun 14.
Parkinson's disease (PD) is surprisingly heterogeneous: some patients have a prominent resting tremor, while others never develop this symptom. Here we investigate whether the functional organization of the voluntary motor system differs between PD patients with and without resting tremor, and whether these differences relate to the cerebral circuit producing tremor. We compared 18 PD patients with marked tremor, 20 PD patients without tremor, and 19 healthy controls. Subjects performed a controlled motor imagery task during fMRI scanning. We quantified imagery-related cerebral activity by contrasting imagery of biomechanically difficult and easy movements. Tremor-related activity was identified by relating cerebral activity to fluctuations in tremor amplitude, using electromyography during scanning. PD patients with tremor had better behavioral performance than PD patients without tremor. Furthermore, tremulous PD patients showed increased imagery-related activity in somatosensory area 3a, as compared with both healthy controls and to nontremor PD patients. This effect was independent from tremor-related activity, which was localized to the motor cortex, cerebellum, and thalamic ventral intermediate nucleus (VIM). The VIM, with known projections to area 3a, was unique in showing both tremor- and imagery-related responses. We conclude that parkinsonian tremor influences motor imagery by modulating central somatosensory processing through the VIM. This mechanism may explain clinical differences between PD patients with and without tremor.
帕金森病（PD）的表现出人意料地具有异质性：一些患者有明显的静止性震颤，而另一些患者则从未出现过这种症状。在这里，我们研究了是否有静止性震颤的 PD 患者与无静止性震颤的 PD 患者之间自愿运动系统的功能组织存在差异，以及这些差异是否与产生震颤的大脑回路有关。我们比较了 18 名震颤明显的 PD 患者、20 名无震颤的 PD 患者和 19 名健康对照者。受试者在 fMRI 扫描期间进行了受控的运动想象任务。我们通过对比生物力学上困难和容易的运动想象来量化与想象相关的大脑活动。通过使用扫描期间的肌电图将大脑活动与震颤幅度的波动相关联，来确定与震颤相关的活动。有震颤的 PD 患者的行为表现优于无震颤的 PD 患者。此外，震颤性 PD 患者的体感区 3a 的与想象相关的活动增加，与健康对照组和非震颤性 PD 患者相比。这种效果独立于震颤相关的活动，震颤相关的活动定位于运动皮层、小脑和丘脑腹侧中间核（VIM）。VIM 通过已知的向区 3a 的投射，是唯一同时显示震颤和想象相关反应的区域。我们的结论是，帕金森病震颤通过 VIM 调节中枢体感处理来影响运动想象。这种机制可能解释了有震颤和无震颤的 PD 患者之间的临床差异。
