Transcranial vibration stimulation at 40 Hz induced neural activity and promoted the coupling of global brain activity and cerebrospinal fluid flow

BACKGROUND: Neuroscience advances have highlighted the potential of non-invasive brain stimulation in influencing cognitive and emotional processes. Conventional stimulation methods such as electrical, magnetic, and ultrasound have been studied intensively, but little is known about the mechanical stimulation. OBJECTIVE: To investigate the effects of 40 Hz transcranial vibration stimulation (TVS) on human brain activity, specifically focusing on changes in the Amplitude of Low-Frequency Fluctuation (ALFF), fractional ALFF (fALFF) and Regional Homogeneity (ReHo) as measures of spontaneous brain activity. Additionally, this study investigates alterations in the global blood-oxygen-level-dependent (gBOLD) signal and cerebrospinal fluid (CSF) inflow coupling, which serve as indicators of glymphatic system function. METHODS: A custom-built head actuator was used to apply 40 Hz TVS to human brain. Functional magnetic resonance imaging (fMRI) were performed before and after 5 mins TVS to explore the changes in ALFF and fALFF and the coupling of global brain activity with cerebrospinal fluid flow (CSF), which is related to the glymphatic clearance. RESULTS: Significant increases were observed in both ALFF and fALFF metrics, indicating that 40 Hz TVS effectively enhanced spontaneous brain activity. Additionally, 40 Hz TVS promoted the synchronization of overall brain activity with CSF, suggesting an improvement in glymphatic clearance processes, an effect that 30 Hz or 50 Hz TVS did not replicate. CONCLUSION: Non-invasive brain stimulation using TVS provided important implications for modulating brain physiology and showed prospective therapeutic benefits for neurological diseases.