Effects of Local Vibration on Sensorimotor Cortical Activity

Background Introduction

Local Vibration (LV) is a technique that applies high-frequency (≥100 Hz) and low-amplitude ( mm) vibrations to muscles or tendons. Studies have shown that LV can promote brain plasticity through repeated activation of Ia afferents, but the specific mechanisms remain unclear. LV has been widely used in rehabilitation medicine and sports training, particularly showing significant effects in improving motor function and reducing spasticity in stroke patients. However, the acute effects of LV on brain cortical activity and its underlying neurophysiological mechanisms require further investigation.

The aim of this study was to explore the acute effects of 30 minutes of local vibration on the sensorimotor cortex (including the primary motor cortex M1, primary somatosensory cortex S1, and posterior parietal cortex PPC) of the flexor carpi radialis (FCR) muscle. By recording electroencephalography (EEG) signals, the research team aimed to reveal how LV affects cortical activity through sensory afferent pathways and to investigate its potential neuroplasticity mechanisms.

Source of the Paper

This paper was co-authored by Clara Pfenninger, Marie Fabre, Narimane Zeghoudi, Ahmed Adham, Charles-Etienne Benoit, and Thomas Lapole. The research team is affiliated with the Laboratoire Interuniversitaire de Biologie de la Motricité at the University of Jean Monnet Saint-Étienne, as well as the University of Lyon and the University of Savoie Mont Blanc in France. The paper was published in 2025 in the Journal of Neurophysiology.

Research Process and Experimental Design

Study Participants and Experimental Design

The study recruited 16 healthy participants (10 males, 6 females) with an average age of 27±6 years. All participants were free from neurological diseases or musculoskeletal injuries. The experiment was divided into three phases: baseline measurement (Con-1), control measurement after 10 minutes of rest (Con-2), and measurement after 30 minutes of local vibration (Post-Vib).

Experimental Procedure

1. Baseline Measurement: Participants first performed a warm-up of 10 submaximal isometric contractions, followed by three maximal voluntary contractions (MVCs) to determine the target force (10% MVC) for subsequent experiments.
2. Local Vibration Intervention: The LV device applied vibration to the right FCR muscle at a frequency of 100 Hz and an amplitude of 1 mm. Each vibration session lasted 10 minutes, with three sessions in total, separated by 1-minute rest intervals.
3. EEG Recording: At baseline, control, and post-vibration, participants performed 30 isometric wrist flexion contractions while EEG signals were recorded. EEG signals were collected using a 64-channel electrode cap with a sampling rate of 2048 Hz.

Data Analysis

After preprocessing (including filtering, denoising, and segmentation), EEG signals were analyzed using Brainstorm software for source localization and time-frequency analysis. The study focused on event-related desynchronization (ERD) and synchronization (ERS) in the α (8-12 Hz) and β (15-35 Hz) frequency bands. Source localization techniques were used to reduce the effects of volume conduction and improve spatial resolution.

Main Results

1. Contraction Preparation Phase

During the contraction preparation phase, α-band desynchronization significantly increased in the M1, S1, and PPC regions after vibration (Post-Vib) (p < 0.05), indicating enhanced cortical activity in these areas. β-band desynchronization also significantly increased in the M1 and S1 regions (p < 0.05), but not in the PPC region (p = 0.07).

2. Contraction Initiation Phase

During the contraction initiation phase, α-band desynchronization significantly increased in the M1, S1, and PPC regions (p < 0.05). β-band desynchronization significantly increased in the M1 and S1 regions (p < 0.05), but not in the PPC region (p = 0.07).

3. Force Plateau Phase

During the force plateau phase, α-band desynchronization significantly increased in the M1, S1, and PPC regions (p < 0.05), while β-band desynchronization showed no significant changes (p > 0.05). This suggests that the enhanced cortical activity after vibration was primarily reflected in the α band.

4. Relaxation Phase

During the relaxation phase, no significant changes were observed in α- and β-band desynchronization (p > 0.05), indicating that vibration had minimal effects on cortical activity during relaxation.

Conclusions and Significance

This study demonstrates that 30 minutes of local vibration can significantly increase activity in the sensorimotor cortex (M1, S1) and posterior parietal cortex (PPC), particularly during the contraction preparation and initiation phases. This enhanced cortical activity may be due to LV-induced Ia afferent discharges projecting to cortical areas through sensory afferent pathways, thereby triggering brain plasticity. The findings provide neurophysiological evidence for the application of LV in rehabilitation medicine and lay the foundation for future research on the long-term effects of repeated LV interventions.

Research Highlights

1. First Source-Level Analysis of EEG Signals: Using source localization techniques, the research team was able to more accurately infer activity in the M1, S1, and PPC regions, reducing the effects of volume conduction.
2. Revealed Acute Effects of LV on Sensorimotor Cortex: The study systematically demonstrated for the first time how LV affects cortical activity through sensory afferent pathways.
3. Provided Theoretical Support for Clinical Applications of LV: The findings offer new neurophysiological evidence for the use of LV in stroke rehabilitation and sports training.

Additional Valuable Information

The research team also noted that future studies should further explore the long-term effects of repeated LV interventions on brain plasticity and consider their application in different patient populations. Additionally, the study data have been made publicly available for further analysis and validation by other researchers.