Changes in theta and gamma oscillations of the medial prefrontal cortex following hippocampal-focused ultrasound stimulation

Abstract

Objective: Neuromodulation is a rapidly growing field of treatment, encompassing implantable and noninvasive technology-based approaches. Focused ultrasound (FUS), a noninvasive method, has the potential to modulate neural activity in deep brain regions with spatial precision based on the penetrance of sound waves into the bone and soft tissue. However, neuromodulation is limited by the inability to confirm modulation in real-time. Electrophysiological technology is required to overcome this limitation. In this study, we aimed to confirm neural activity using Neuropixel electrodes during FUS sonication.Methods: Six male C57BL/6 mice were subjected to ultrasound sonication in the hippocampus. Simultaneously, local field potential (LFP) measurements were performed using Neuropixel electrodes. The experimental groups were divided into three categories: before, during, and after FUS sonication and the measured LFP data were compared between groups.Results: Theta and gamma waves were extracted from the recorded LFP data and compared between the groups. The theta and gamma oscillations changed after FUS sonication compared to before. The theta graph showed significant changes between the pre- and during-treatment groups and between the during- and post-treatment groups (theta: 4–8 Hz, F=23.91, p<0.0001). However, the gamma graph did not show significant changes in any groups (gamma: 30–50 Hz). Additionally, the expression of c-fos, a marker of neuronal activity, increased after FUS sonication.Conclusion: Although further research is needed—including longer follow-up LFP measurements after FUS sonication and the collection of more LFP data—neuromodulation with FUS can be considered usable in other neurological disease models.