OPM-MEG Measuring Phase Synchronization on Source Time Series: Application in Rhythmic Median Nerve Stimulation

Area of Science:

• Neuroscience
• Biophysics
• Biomedical Engineering

Background:

• Optically pumped magnetometers (OPMs) offer a promising alternative to traditional cryogenic superconducting quantum interference devices for magnetoencephalography (MEG).
• Phase synchronization analysis is crucial for understanding brain oscillations and functional connectivity.
• Validating OPM-MEG's capability in phase synchronization measurement is essential for its broader adoption in neuroscience research.

Purpose of the Study:

• To evaluate the feasibility and fidelity of OPM-MEG in measuring phase synchronization and functional connectivity.
• To investigate the impact of rhythmic versus arrhythmic somatosensory stimulation on brain activity.
• To analyze source-level phase synchronization patterns in the somatosensory cortex.

Main Methods:

• Utilized an array of OPMs for OPM-MEG recordings.
• Measured evoked responses to 20Hz rhythmic and arrhythmic median nerve stimulation.
• Analyzed inter-trial phase synchronization (ITPS) and inter-regional phase synchronization (IRPS) in the primary (SI) and secondary (SII) somatosensory cortices using source-level time series analysis.

Main Results:

• Rhythmic stimulation induced continuous oscillations and phase resetting in SI and SII.
• ITPS and IRPS significantly increased at 20Hz and 40Hz under rhythmic stimulation, unlike arrhythmic stimulation.
• Initial stimulation stages showed higher ITPS and IRPS at Mu rhythm during rhythmic stimulation compared to arrhythmic.

Conclusions:

• OPM-MEG accurately measures source-level phase patterns and functional connectivity.
• The findings support OPM-MEG's utility in studying neural mechanisms underlying rhythmic stimulation therapies for rehabilitation.