tFUS stimulation of the contralesional motor cortex in an MCAO ischemic stroke rat model to restore interhemispheric balance

Abstract

Objectives: We aim to investigate the effects of suppressive tFUS applied to the contralesional motor cortex in an ischemic stroke rat model to restore interhemispheric balance.

Methods: An ischemic stroke model was prepared using male Sprague-Dawley rats？with 90-min middle cerebral artery occlusion (MCAO) in the right hemisphere, followed by reperfusion. On post-MCAO days 0 and 3, 300-kHz tFUS sonication was delivered to the contralesional M1 at 2.53 W/cm2？Isppa for 20-min, with a suppressive pulsing scheme at 5% duty cycle and 40-Hz pulse repetition frequency. 10-min EEG recording was conducted over the bilateral parietal cortices before and after each tFUS session.？

Results: In post-MCAO day 0, animals were categorized by severity, based on the pairwise-derived brain-symmetry index (pdBSI) of delta oscillations. Following tFUS sessions, regardless of stroke severity, the relative power of ipsilesional delta showed a trend to increase on day 3 compared to day 0, while the pdBSI decreased only in severe-stroke rats, indicating a recovery of interhemispheric balance. In the case of the control stroke-group (without sonication), most of the severe-stroke animals were not able to survive during the study period, and the relative power of ipsilesional delta did not increase on day 3 compared to day 0.

Conclusions: These results suggest the potential therapeutic efficacy of tFUS-mediated suppression of abnormal hyperexcitability of the contralesional hemisphere in ischemic strokes. The restoration of interhemispheric balance using tFUS neuromodulation would help facilitate post-stroke rehabilitation. The tFUS technique may also be conducive to increasing post-stroke acute survival rate, warranting further investigations.