Weak Ultrasound Contributes to Neuromodulatory Effects in the Rat Motor Cortex

Abstract

Transcranial focused ultrasound (tFUS) is a novel neuromodulating technique. It has been demonstrated that the neuromodulatory effects can be induced by weak ultrasound exposure levels (spatial-peak temporal average intensity, ISPTA < 10 mW/cm2) in vitro. However, fewer studies have examined the use of weak tFUS to potentially induce long-lasting neuromodulatory responses in vivo. The purpose of this study was to determine the lower-bound threshold of tFUS stimulation for inducing neuromodulation in the motor cortex of rats. A total of 94 Sprague–Dawley rats were used. The sonication region aimed at the motor cortex under weak tFUS exposure (ISPTA of 0.338–12.15 mW/cm2). The neuromodulatory effects of tFUS on the motor cortex were evaluated by the changes in motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS). In addition to histology analysis, the in vitro cell culture was used to confirm the neuromodulatory mechanisms following tFUS stimulation. In the results, the dose-dependent inhibitory effects of tFUS were found, showing increased intensities of tFUS suppressed MEPs and lasted for 30 min. Weak tFUS significantly decreased the expression of excitatory neurons and increased the expression of inhibitory GABAergic neurons. The PIEZO-1 proteins of GABAergic neurons were found to involve in the inhibitory neuromodulation. In conclusion, we show the use of weak ultrasound to induce long-lasting neuromodulatory effects and explore the potential use of weak ultrasound for future clinical neuromodulatory applications.

Innovation at the Intersection: Emerging Translational Research in Neurology and Psychiatry

“…The first paper investigates the effects of weak ultrasound on the rat motor cortex, and suggests that it can induce neuromodulation without causing tissue damage [77]. The authors used functional MRI (fMRI) and electrophysiological recordings to measure the changes in blood-oxygen-level-dependent (BOLD) signals and local field potentials (LFPs) in response to ultrasound stimulation.…”

Neurodegeneration in Cognitive Impairment and Mood Disorders for Experimental, Clinical and Translational Neuropsychiatry

“…Hence, there is a requirement for new and inventive methods, such as non-invasive brain stimulation, that can regulate neural activity and plasticity in a secure and reversible manner [ 17 , 18 , 19 , 20 , 21 ]. The field is rapidly evolving, with a focus on identifying new avenues of clinical research, elucidating potential mechanisms for the therapeutic effects of non-invasive brain stimulation (NIBS) and exploring the potential synergy between different stimulation protocols and pharmacological interventions [ 22 , 23 , 24 , 25 , 26 , 27 ].…”

Update on Non-invasive Brain Stimulation on Stroke Motor Impairment: A Narrative Review

“…By adjusting the frequency of these waves (i.e., low-frequency range of 200–700 kHz), tFUS can penetrate deeper and with greater spatial specificity [ 31 ]. Although some animal studies have been conducted supporting the effectiveness of tFUS on neuromodulation [ 32 33 34 ], studies on motor impairment after stroke in patients are yet scarce.…”