Xie Ping, Zhou Sa, Wang Xingran, Wang Yibo, Yuan Yi
Institute of Electric Engineering, Yanshan University, Qinhuangdao, 066004, Hebei, China.
BMC Neurosci. 2018 Oct 3;19(1):60. doi: 10.1186/s12868-018-0462-8.
Pulsed transcranial ultrasound stimulation (pTUS) can modulate the neuronal activity of motor cortex and elicit muscle contractions. Cortico-muscular coupling (CMC) can serve as a tool to identify interaction between the oscillatory activity of the motor cortex and effector muscle. This research aims to explore the neuromodulatory effect of low-intensity, pTUS with different number of tone burst to neural circuit of motor-control system by analyzing the coupling relationship between motor cortex and tail muscle in mouse. The motor cortex of mice was stimulated by pulsed transcranial ultrasound with different number of tone bursts (NTB = 100 150 200 250 300). The local field potentials (LFPs) in tail motor cortex and electromyography (EMG) in tail muscles were recorded simultaneously during pTUS. The change of integral coupling strength between cortex and muscle was evaluated by mutual information (MI). The directional information interaction between them were analyzed by transfer entropy (TE).
Almost all of the MI and TE values were significantly increased by pTUS. The results of MI showed that the CMC was significantly enhanced with the increase of NTB. The TE results showed the coupling strength of CMC in descending direction (from LFPs to EMG) was significantly higher than that in ascending direction (from EMG to LFPs) after stimulation. Furthermore, compared to NTB = 100, the CMC in ascending direction were significantly enhanced when NTB = 250, 300, and CMC in descending direction were significantly enhanced when NTB = 200, 250, 300.
These results confirm that the CMC between motor cortex and the tail muscles in mouse could be altered by pTUS. And by increasing the NTB (i.e. sonication duration), the coupling strength within the cortico-muscular circuit could be increased, which might further influence the motor function of mice. It demonstrates that, using MI and TE method, the CMC could be used for quantitatively evaluating the effect of pTUS with different NTBs, which might provide a new insight into the effect of pTUS neuromodulation in motor cortex.
脉冲经颅超声刺激（pTUS）可调节运动皮层的神经元活动并引发肌肉收缩。皮质-肌肉耦合（CMC）可作为一种工具，用于识别运动皮层的振荡活动与效应器肌肉之间的相互作用。本研究旨在通过分析小鼠运动皮层与尾肌之间的耦合关系，探讨不同脉冲串数量的低强度pTUS对运动控制系统神经回路的神经调节作用。用不同脉冲串数量（NTB = 100、150、200、250、300）的脉冲经颅超声刺激小鼠的运动皮层。在pTUS期间，同时记录尾运动皮层的局部场电位（LFPs）和尾肌的肌电图（EMG）。通过互信息（MI）评估皮层与肌肉之间积分耦合强度的变化。通过转移熵（TE）分析它们之间的方向信息相互作用。
几乎所有的MI和TE值都因pTUS而显著增加。MI结果表明，CMC随NTB的增加而显著增强。TE结果表明，刺激后CMC在下行方向（从LFPs到EMG）的耦合强度显著高于上行方向（从EMG到LFPs）。此外，与NTB = 100相比，当NTB = 250、300时，上行方向的CMC显著增强；当NTB = 200、250、300时，下行方向的CMC显著增强。
这些结果证实，pTUS可改变小鼠运动皮层与尾肌之间的CMC。并且通过增加NTB（即超声处理持续时间），皮质-肌肉回路内的耦合强度可以增加，这可能进一步影响小鼠的运动功能。结果表明，使用MI和TE方法，CMC可用于定量评估不同NTB的pTUS的效果，这可能为pTUS对运动皮层神经调节作用提供新的见解。
