Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160-7336, USA.
J Neurophysiol. 2013 Sep;110(5):1180-9. doi: 10.1152/jn.00172.2012. Epub 2013 Jun 5.
High-frequency, long-duration intracortical microstimulation (HFLD-ICMS) applied to motor cortex is recognized as a useful and informative method for corticomotor mapping by evoking natural-appearing movements of the limb to consistent stable end-point positions. An important feature of these movements is that stimulation of a specific site in motor cortex evokes movement to the same spatial end point regardless of the starting position of the limb. The goal of this study was to delineate effective stimulus parameters for evoking forelimb movements to stable spatial end points from HFLD-ICMS applied to primary motor cortex (M1) in awake monkeys. We investigated stimulation of M1 as combinations of frequency (30-400 Hz), amplitude (30-200 μA), and duration (0.5-2 s) while concurrently recording electromyographic (EMG) activity from 24 forelimb muscles and movement kinematics with a motion capture system. Our results suggest a range of parameters (80-140 Hz, 80-140 μA, and 1,000-ms train duration) that are effective and safe for evoking forelimb translocation with subsequent stabilization at a spatial end point. The mean time for stimulation to elicit successful movement of the forelimb to a stable spatial end point was 475.8 ± 170.9 ms. Median successful frequency and amplitude were 110 Hz and 110 μA, respectively. Attenuated parameters resulted in inconsistent, truncated, or undetectable movements, while intensified parameters yielded no change to movement end points and increased potential for large-scale physiological spread and adverse focal motor effects. Establishing cortical stimulation parameters yielding consistent forelimb movements to stable spatial end points forms the basis for a systematic and comprehensive mapping of M1 in terms of evoked movements and associated muscle synergies. Additionally, the results increase our understanding of how the central nervous system may encode movement.
高频、长时程皮层内微刺激（HFLD-ICMS）应用于运动皮层，被认为是一种有用且信息量丰富的皮质运动映射方法，它通过诱发出肢体的自然运动，使肢体到达一致且稳定的终点位置。这些运动的一个重要特征是，刺激运动皮层的特定部位会引起运动，而与肢体的起始位置无关，运动都会到达相同的空间终点。本研究的目的是确定应用于清醒猴子初级运动皮层（M1）的 HFLD-ICMS 诱发稳定空间终点的前肢运动的有效刺激参数。我们研究了 M1 的刺激，刺激参数组合为频率（30-400 Hz）、振幅（30-200 μA）和时长（0.5-2 s），同时记录来自 24 个前肢肌肉的肌电图（EMG）活动和运动学，运动学使用运动捕捉系统进行记录。我们的结果表明，有一系列参数（80-140 Hz、80-140 μA 和 1000-ms 刺激时长）是有效的，且安全的，可诱发前肢移动，并随后在空间终点稳定下来。刺激诱发前肢成功到达稳定空间终点的平均时间为 475.8±170.9 ms。成功的刺激频率和振幅中位数分别为 110 Hz 和 110 μA。减弱的参数导致运动不连续、截断或无法检测，而增强的参数则不会改变运动终点，并增加了大范围生理扩散和不利的局灶性运动效应的可能性。确定产生一致的前肢运动到达稳定空间终点的皮层刺激参数，为从诱发运动和相关肌肉协同作用的角度全面系统地绘制 M1 奠定了基础。此外，这些结果增加了我们对中枢神经系统如何编码运动的理解。
