Institute of Electric Engineering, Yanshan University, Qinhuangdao, Hebei 066004, People's Republic of China.
J Neural Eng. 2019 Apr;16(2):026036. doi: 10.1088/1741-2552/ab0879. Epub 2019 Feb 19.
Low-intensity pulsed ultrasound stimulation (LIPUS) targeted to the mouse motor cortex can simultaneously induce local field potentials (LFPs) and electromyogram (EMG) responses. However, the functional coupling relationship between LFP and EMG signals has not been elucidated to date. This study aimed to investigate the phase synchronization between LFP and EMG signals induced by LIPUS over the mouse motor cortex.
LIPUS at 500 kHz with varied sonication intensities and duty cycles (DCs), was delivered to the mouse motor cortex. LFPs of the motor cortex and EMG responses of the tail were simultaneously recorded during LIPUS. We then evaluated two control groups using the same experimental parameters, but changed the position of EMG recording to the hind leg and the ultrasound stimulus target to the primary visual cortex. The phase synchronization between LFPs and EMG signals was evaluated by performing a phase locking value (PLV) analysis in the time-frequency domain and was compared across specific frequency bands.
The results showed that LIPUS increased the phase synchronization in a broad frequency band (5-150 Hz), and the maximum duration of the increased PLV was stable at approximately 200 ms. It is worth noting that the sonication parameters directly affected the time-frequency domain distribution of cortico-muscular synchronization. Specifically, significant alpha and beta synchronization appeared at 0.2 and 0.4 W cm I stimulation, while gamma synchronization occurred at 0.8 and 1.1 W cm I stimulation. The synchronization in all frequency bands apparently increased at 30% DC. Beta synchronization weakened when the DC was less than 30%. Furthermore, no significant phase synchronization was observed in the two control groups.
Considering the close association between specific motor function and cortical-muscular synchronization in different frequency bands, we suggest that LIPUS over the motor cortex could selectively modulate motor function via different sonication parameters. Additionally, the phase synchronization between LFPs and EMG might be an invaluable index for assessing the ultrasonic effect on the motor system, which could be used in future clinical research to optimize ultrasound parameters. Thus, this study provides new insight into evaluating the neuromodulatory effects of ultrasound on motor function, thereby supporting the therapeutic application of ultrasound in neurological disorders characterized by motor deficits.
针对小鼠运动皮层的低强度脉冲超声刺激（LIPUS）可以同时诱导局部场电位（LFP）和肌电图（EMG）反应。然而，LFP 和 EMG 信号之间的功能耦合关系尚未阐明。本研究旨在探讨 LIPUS 刺激小鼠运动皮层时 LFP 和 EMG 信号之间的相位同步。
使用 500kHz 的 LIPUS，改变超声强度和占空比（DC），施加于小鼠运动皮层。在 LIPUS 过程中同时记录运动皮层的 LFP 和尾巴的 EMG 反应。然后，我们使用相同的实验参数评估了两个对照组，但将 EMG 记录的位置更改为后腿，并将超声刺激的目标更改为初级视觉皮层。通过在时频域中进行相位锁定值（PLV）分析来评估 LFP 和 EMG 信号之间的相位同步，并在特定频带之间进行比较。
结果表明，LIPUS 在较宽的频带（5-150Hz）中增加了相位同步，增加的 PLV 的最大持续时间约为 200ms 稳定。值得注意的是，超声参数直接影响皮质肌同步的时频域分布。具体来说，在 0.2 和 0.4W cm I 刺激下出现显著的 alpha 和 beta 同步，而在 0.8 和 1.1W cm I 刺激下出现 gamma 同步。在 DC 小于 30%时，beta 同步减弱。此外，在两个对照组中没有观察到明显的相位同步。
考虑到特定运动功能与不同频带皮质肌同步之间的密切关系，我们建议运动皮层上的 LIPUS 可以通过不同的超声参数选择性地调节运动功能。此外，LFP 和 EMG 之间的相位同步可能是评估超声对运动系统影响的一个非常有价值的指标，可用于未来的临床研究中以优化超声参数。因此，本研究为评估超声对运动功能的神经调节作用提供了新的见解，从而支持超声在以运动缺陷为特征的神经疾病中的治疗应用。
