Laboratory for Neuro- and Psychophysiology, KU Leuven, 3000, Leuven, Belgium.
Leuven Brain Institute, KU Leuven, 3000, Leuven, Belgium.
Sci Rep. 2021 Feb 24;11(1):4511. doi: 10.1038/s41598-021-83904-8.
The neural mechanisms underlying the effects of continuous Theta-Burst Stimulation (cTBS) in humans are poorly understood. Animal studies can clarify the effects of cTBS on individual neurons, but behavioral evidence is necessary to demonstrate the validity of the animal model. We investigated the behavioral effect of cTBS applied over parietal cortex in rhesus monkeys performing a visually-guided grasping task with two differently sized objects, which required either a power grip or a pad-to-side grip. We used Fitts' law, predicting shorter grasping times (GT) for large compared to small objects, to investigate cTBS effects on two different grip types. cTBS induced long-lasting object-specific and dose-dependent changes in GT that remained present for up to two hours. High-intensity cTBS increased GTs for a power grip, but shortened GTs for a pad-to-side grip. Thus, high-intensity stimulation strongly reduced the natural GT difference between objects (i.e. the Fitts' law effect). In contrast, low-intensity cTBS induced the opposite effects on GT. Modifying the coil orientation from the standard 45-degree to a 30-degree angle induced opposite cTBS effects on GT. These findings represent behavioral evidence for the validity of the nonhuman primate model to study the neural underpinnings of non-invasive brain stimulation.
持续 theta 爆发刺激（cTBS）对人类影响的神经机制尚不清楚。动物研究可以阐明 cTBS 对单个神经元的影响，但需要行为证据来证明动物模型的有效性。我们在执行视觉引导抓取任务的恒河猴的顶叶皮层上施加 cTBS，该任务需要使用力量抓握或垫到侧握来抓取两种不同大小的物体。我们使用 Fitts 定律，预测较大物体的抓取时间（GT）比小物体短，来研究 cTBS 对两种不同握法的影响。cTBS 诱导了与物体特异性和剂量依赖性相关的持久 GT 变化，这些变化在两小时内仍然存在。高强度 cTBS 增加了力量抓握的 GT，但缩短了垫到侧握的 GT。因此，高强度刺激强烈减少了物体之间自然 GT 差异（即 Fitts 定律效应）。相比之下，低强度 cTBS 对 GT 产生了相反的影响。将线圈方向从标准的 45 度调整为 30 度，会对 GT 产生相反的 cTBS 影响。这些发现为非人类灵长类动物模型研究非侵入性脑刺激的神经基础提供了行为证据。
