Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO 63130, United States of America.
Department of Anesthesiology and Pain Medicine. Center for Neurobiology of Addiction, Pain, and Emotion. University of Washington, Seattle, WA 98195, United States of America.
Phys Med Biol. 2021 Jun 24;66(13). doi: 10.1088/1361-6560/ac08b1.
The objective of this study was to compare focused ultrasound (FUS) neuromodulation-induced motor responses under two physical mechanisms: mechanical and mechanothermal effects. Mice were divided into two groups. One group was subjected to short-duration FUS stimulation (0.3 s) that induced mechanical effects (mechanical group). The other group underwent long-duration FUS stimulation (15 s) that produced not only mechanical but also thermal effects (mechanothermal group). FUS was targeted at the deep cerebellar nucleus in the cerebellum to induce motor responses, which were evaluated by recording the evoked electromyographic (EMG) signals and tail movements. Brain tissue temperature rise associated with the FUS stimulation was quantified by noninvasive magnetic resonance thermometry. Temperature rise was negligible for the mechanical group (0.2 °C ± 0.1 °C) but did rise within the range of 0.6 °C ± 0.2 °C-3.3 °C ± 0.9 °C for the mechanothermal group. The elongated FUS beam also induced heating in the dorsal brain (below the top skull) and ventral brain (above the bottom skull) along the beam path for the mechanothermal group. Both mechanical and mechanothermal groups achieved successful FUS neuromodulation. EMG response latencies were within the range of 0.03-0.1 s at different intensity levels for the mechanical group. The mechanothermal effect of FUS could induce both short-latency EMG (0.2-1.4 s) and long-latency EMG (8.7-13.0 s) under the same intensity levels as the mechanical group. The different temporal dynamics of evoked EMG suggested that FUS-induced mechanical and mechanothermal effects could evoke different responses in the brain.
本研究旨在比较两种物理机制下聚焦超声（FUS）神经调节诱导的运动反应：机械效应和机械热效应。将小鼠分为两组。一组接受短时间 FUS 刺激（0.3 s），诱导机械效应（机械组）。另一组接受长时间 FUS 刺激（15 s），产生机械和热效应（机械热组）。FUS 靶向小脑深部核团以诱导运动反应，通过记录诱发的肌电图（EMG）信号和尾巴运动来评估。通过非侵入性磁共振测温来量化与 FUS 刺激相关的脑组织温升。机械组的温升可忽略不计（0.2°C±0.1°C），但机械热组的温升范围在 0.6°C±0.2°C-3.3°C±0.9°C。对于机械热组，拉长的 FUS 光束还会沿光束路径在大脑背部（颅顶以下）和大脑腹部（颅底以上）引起加热。机械组和机械热组均成功实现了 FUS 神经调节。在机械组的不同强度水平下，EMG 反应潜伏期在 0.03-0.1 s 范围内。FUS 的机械热效应可在与机械组相同的强度水平下诱导短潜伏期 EMG（0.2-1.4 s）和长潜伏期 EMG（8.7-13.0 s）。诱发 EMG 的不同时间动态表明，FUS 诱导的机械和机械热效应可在大脑中引起不同的反应。
