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Modulation effect of mouse hippocampal neural oscillations by closed-loop transcranial ultrasound stimulation

Objective. Closed-loop transcranial ultrasound stimulation (TUS) can be applied at a specific time according to the state of neural activity to achieve timely and precise neuromodulation and improve the modulation effect. In a previous study, we found that closed-loop TUS at the peaks and troughs of the theta rhythm in the mouse hippocampus was able to increase the absolute power and decrease the relative power of the theta rhythm of local field potentials (LFPs) independent of the peaks and troughs of the stimulus. However, it remained unclear whether the modulation effect of this closed-loop TUS-induced mouse hippocampal neural oscillation depended on the peaks and troughs of the theta rhythm. Approach. In this study, we used ultrasound with different stimulation modes and durations to stimulate the peaks (peak stimulation) and troughs (trough stimulation) of the hippocampal theta rhythm. The LFPs in the area of ultrasound stimulation were recorded and the amplitudes and power spectra of the theta rhythm before and after ultrasound stimulation were analyzed. Main results. The results showed that (a) the relative change in amplitude of theta rhythm decreases as the number of stimulation trials under peak stimulation increases; (b) the relative change in the absolute power of the theta rhythm decreases as the number of stimulation trials under peak stimulation increases; (c) the relative change in amplitude of the theta rhythm increases nonlinearly with the stimulation duration (SD) under peak stimulation, and; (d) the relative change in absolute power exhibits a nonlinear increase with SD under peak stimulation. Significance. These results suggest that the modulation effect of closed-loop TUS on theta rhythm is dependent on the stimulation mode and duration under peak stimulation. TUS has the potential to precisely modulate theta rhythm-related neural activity.