Department of Biomedical Engineering, City College of New York, United States.
Department of Biomedical Engineering, Columbia University, United States.
Brain Stimul. 2022 Jan-Feb;15(1):233-243. doi: 10.1016/j.brs.2022.01.002. Epub 2022 Jan 3.
Owing to its high spatial resolution and penetration depth, transcranial focused ultrasound stimulation (tFUS) is one of the most promising approaches to non-invasive neuromodulation. Identifying the impact of endogenous neural activity on neuromodulation outcome is critical to harnessing the potential of tFUS.
Here we sought to identify the relationship between pre-stimulation neural activity and the neuronal response to tFUS.
We applied 3 min of continuous-wave tFUS to the hippocampal region of the rat while recording local field potentials (LFP) and multi-unit activity (MUA) from the target. We also tested the application of tFUS but with an air gap separating the transducer and the skull, as well as active stimulation of the contralateral olfactory bulb.
We observed a modest but significant increase in firing rate during hippocampal tFUS, but not during stimulation of the olfactory bulb or when an air gap was present. Importantly, the observed firing rate increase was significantly modulated by the power of baseline oscillations in the LFP, with low levels of delta (1-3 Hz) and high levels of theta (4-10 Hz) and gamma (30-250 Hz) power producing significantly larger firing rate increases. Firing rate increases were also amplified by a factor of 7× when stimulation was applied during periods of frequent sharp-wave ripple (SWR) activity.
Our findings suggest that baseline brain rhythms may effectively "gate" the response to tFUS.
由于其具有较高的空间分辨率和穿透深度，经颅聚焦超声刺激（tFUS）是一种很有前途的非侵入性神经调节方法。确定内源性神经活动对神经调节结果的影响对于利用 tFUS 的潜力至关重要。
本研究旨在确定刺激前神经活动与 tFUS 引起的神经元反应之间的关系。
我们在大鼠海马区施加 3 分钟的连续波 tFUS，同时记录目标区域的局部场电位（LFP）和多单位活动（MUA）。我们还测试了在换能器和颅骨之间存在气隙以及对侧嗅球进行主动刺激的情况下 tFUS 的应用。
我们观察到在海马区 tFUS 刺激期间，神经元的发放率有适度但显著的增加，但在嗅球刺激或存在气隙时没有观察到这种增加。重要的是，观察到的发放率增加与 LFP 中的基线振荡功率显著相关，低水平的 delta（1-3 Hz）和高水平的 theta（4-10 Hz）和 gamma（30-250 Hz）功率产生显著更大的发放率增加。当刺激应用于频繁的尖波涟漪（SWR）活动期间时，发放率增加还被放大了 7 倍。
我们的发现表明，基线脑节律可能有效地“门控”对 tFUS 的反应。
