Human motor cortical activity is selectively phase-entrained on underlying rhythms.

Area of Science:

• Neuroscience
• Motor Control
• Brain Rhythms

Background:

• The functional role of brain electrical rhythms, particularly the beta rhythm (12-20 Hz) in the motor cortex, is not fully understood.
• Beta rhythm amplitude decreases during movement and is implicated in motor diseases.
• Neuronal population activity and its relationship to brain rhythms during movement require further investigation.

Purpose of the Study:

• To investigate the phase-coupling between neuronal population activity and the beta rhythm in the human motor cortex.
• To determine how this relationship changes during voluntary movement.
• To explore the potential role of beta rhythm phase-entrainment in gating motor function.

Main Methods:

• Utilized subdural electrocorticography (ECoG) electrode arrays in human patients performing simple finger movement tasks.
• Measured local cortical activity, including rhythmic and broadband (aggregate neural population) signals.
• Analyzed phase-coupling between broadband activity and the beta rhythm (12-20 Hz) during rest and movement.

Main Results:

• During fixation, broadband neural activity in the peri-central cortex was phase-entrained to the beta rhythm.
• Finger movements showed somatotopically specific broadband responses on the pre-central gyrus.
• Beta rhythm amplitude decreased diffusely across the motor cortex during movement, independent of specific finger movements.
• Beta phase-entrainment diminished or was eliminated during finger movement.

Conclusions:

• The beta rhythm is not solely a resting rhythm; it actively influences neuronal population dynamics.
• Phase-entrainment of broadband activity by the beta rhythm may represent a mechanism for actively gating or suppressing motor function.
• The findings provide new insights into the dynamic role of beta oscillations in motor control and potential implications for motor disorders.