Department of Neurosurgery, 300 UCLA Stein Plaza, Suite 562, David Geffen School of Medicine at UCLA (University of California, Los Angeles), Los Angeles, CA, USA.
Department of Neurology, 710 Westwood Plaza, David Geffen School of Medicine at UCLA (University of California, Los Angeles), Los Angeles, CA, USA.
Clin Neurophysiol. 2022 Apr;136:237-246. doi: 10.1016/j.clinph.2021.11.077. Epub 2021 Dec 24.
In patients with Parkinson Disease (PD), self-initiated or internally cued (IC) actions are thought to be compromised by the disease process, as exemplified by impairments in action initiation. In contrast, externally-cued (EC) actions which are made in response to sensory prompts can restore a remarkable degree of movement capability in PD, particularly alleviating freezing-of-gait. This study investigates the electrophysiological underpinnings of movement facilitation in PD through visuospatial cuing, with particular attention to the dynamics within the posterior parietal cortex (PPC) and lateral premotor cortex (LPMC) axis of the dorsal visual stream.
Invasive cortical recordings over the PPC and LPMC were obtained during deep brain stimulation lead implantation surgery. Thirteen PD subjects performed an action selection task, which was constituted by left or right joystick movement with directional visual cuing in the EC condition and internally generated direction selection in the IC condition. Time-resolved neural activities within and between the PPC and LPMC were compared between EC and IC conditions.
Reaction times (RT) were significantly faster in the EC condition relative to the IC condition (paired t-test, p = 0.0015). PPC-LPMC inter-site phase synchrony within the β-band (13-35 Hz) was significantly greater in the EC relative to the IC condition. Greater PPC-LPMC β debiased phase lag index (dwPLI) prior to movement onset was correlated with faster reaction times only in the EC condition. Multivariate granger causality (GC) was greater in the EC condition relative to the IC condition, prior to and during movement.
Relative to IC actions, we report relative increase in inter-site phase synchrony and directional PPC to LPMC connectivity in the β-band during preparation and execution of EC actions. Furthermore, increased strength of connectivity is predictive of faster RT, which are pathologically slow in PD patients. Stronger engagement of the PPC-LPMC cortical network by an EC specifically through the channel of β-modulation is implicated in correcting the pathological slowing of action initiation seen in Parkinson's patients.
These findings shed light on the electrophysiological mechanisms that underlie motor facilitation in PD patients through visuospatial cuing.
在帕金森病（PD）患者中，自我发起或内部提示（IC）的动作被认为受到疾病过程的影响，例如在动作启动方面的障碍。相比之下，对外界提示（EC）做出的反应动作可以在 PD 中恢复相当程度的运动能力，特别是减轻步态冻结。本研究通过视觉空间提示研究 PD 中运动促进的电生理基础，特别关注背侧视觉流中顶后皮质（PPC）和外侧运动前皮质（LPMC）轴内的动力学。
在深部脑刺激引线植入手术期间，在 PPC 和 LPMC 上获得了侵入性皮质记录。13 名 PD 患者执行了一个动作选择任务，该任务由左或右操纵杆运动组成，在 EC 条件下具有方向视觉提示，在 IC 条件下内部生成方向选择。比较了 EC 和 IC 条件下 PPC 和 LPMC 内和之间的时间分辨神经活动。
EC 条件下的反应时间（RT）明显快于 IC 条件（配对 t 检验，p = 0.0015）。与 IC 条件相比，β 频段（13-35 Hz）内的 PPC-LPMC 间位相同步性在 EC 条件下显著更大。在运动开始之前，PPC-LPMC 之间的β去偏置相位滞后指数（dwPLI）越大，仅在 EC 条件下与更快的反应时间相关。在运动之前和期间，EC 条件下的多变量格兰杰因果关系（GC）相对大于 IC 条件。
与 IC 动作相比，我们报告在 EC 动作的准备和执行过程中，β 波段内的位相同步性和定向 PPC 到 LPMC 连接性相对增加。此外，连接强度的增加可预测 RT 更快，而 PD 患者的 RT 则较慢。通过β调制通道，特别是通过 EC 来增强 PPC-LPMC 皮质网络的参与，可能有助于纠正帕金森病患者动作启动的病理性迟缓。
这些发现揭示了通过视觉空间提示在 PD 患者中促进运动的电生理机制。
