1 Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany.
Brain. 2013 Dec;136(Pt 12):3659-70. doi: 10.1093/brain/awt271. Epub 2013 Oct 22.
Electrophysiological studies suggest that rest tremor in Parkinson's disease is associated with an alteration of oscillatory activity. Although it is well known that tremor depends on cortico-muscular coupling, it is unclear whether synchronization within and between brain areas is specifically related to the presence and severity of tremor. To tackle this longstanding issue, we took advantage of naturally occurring spontaneous tremor fluctuations and investigated cerebral synchronization in the presence and absence of rest tremor. We simultaneously recorded local field potentials from the subthalamic nucleus, the magnetoencephalogram and the electromyogram of forearm muscles in 11 patients with Parkinson's disease (all male, age: 52-74 years). Recordings took place the day after surgery for deep brain stimulation, after withdrawal of anti-parkinsonian medication. We selected epochs containing spontaneous rest tremor and tremor-free epochs, respectively, and compared power and coherence between subthalamic nucleus, cortex and muscle across conditions. Tremor-associated changes in cerebro-muscular coherence were localized by Dynamic Imaging of Coherent Sources. Subsequently, cortico-cortical coupling was analysed by computation of the imaginary part of coherency, a coupling measure insensitive to volume conduction. After tremor onset, local field potential power increased at individual tremor frequency and cortical power decreased in the beta band (13-30 Hz). Sensor level subthalamic nucleus-cortex, cortico-muscular and subthalamic nucleus-muscle coherence increased during tremor specifically at tremor frequency. The increase in subthalamic nucleus-cortex coherence correlated with the increase in electromyogram power. On the source level, we observed tremor-associated increases in cortico-muscular coherence in primary motor cortex, premotor cortex and posterior parietal cortex contralateral to the tremulous limb. Analysis of the imaginary part of coherency revealed tremor-dependent coupling between these cortical areas at tremor frequency and double tremor frequency. Our findings demonstrate a direct relationship between the synchronization of cerebral oscillations and tremor manifestation. Furthermore, they suggest the feasibility of tremor detection based on local field potentials and might thus become relevant for the design of closed-loop stimulation systems.
电生理学研究表明，帕金森病的静止性震颤与振荡活动的改变有关。虽然众所周知震颤依赖于皮质-肌肉耦合，但尚不清楚脑区内部和之间的同步是否与震颤的存在和严重程度有特定关系。为了解决这个长期存在的问题，我们利用自然发生的自发性震颤波动，研究了在存在和不存在静止性震颤的情况下大脑的同步性。我们同时记录了 11 名帕金森病患者（均为男性，年龄 52-74 岁）的丘脑底核局部场电位、脑磁图和前臂肌肉肌电图。记录是在深部脑刺激手术后的第二天进行的，抗帕金森病药物停药后。我们分别选择包含自发性静止性震颤和无震颤的时期，并比较了条件下丘脑底核、皮质和肌肉之间的功率和相干性。通过相干源动态成像定位与震颤相关的脑-肌相干变化。随后，通过计算相干的虚部来分析皮质-皮质耦合，这是一种对容积传导不敏感的耦合度量。震颤开始后，局部场电位功率在个体震颤频率处增加，皮质功率在β频带（13-30 Hz）处降低。在震颤过程中，丘脑底核-皮质、皮质-肌肉和丘脑底核-肌肉相干性增加，特别是在震颤频率处。丘脑底核-皮质相干性的增加与肌电图功率的增加相关。在源水平上，我们观察到对侧震颤肢体的运动皮层、运动前皮层和顶后皮层的皮质-肌肉相干性与震颤相关增加。相干虚部分析表明，在震颤频率和双震颤频率处，这些皮质区域之间存在震颤依赖性耦合。我们的研究结果表明大脑振荡同步与震颤表现之间存在直接关系。此外，它们还表明基于局部场电位进行震颤检测的可行性，因此可能与闭环刺激系统的设计相关。
