Phase-specific modulation of cortical motor output during movement observation

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Neuroscience

Background:

• The brain's motor system is active not only during action execution but also during action observation.
• Mirror neuron systems are hypothesized to play a role in understanding and imitating observed actions.

Purpose of the Study:

• To investigate how different phases of an observed movement influence cortical motor output.
• To explore the temporal coding aspects of action observation and execution through motor evoked potentials (MEPs).

Main Methods:

• Utilized transcranial magnetic stimulation (TMS) to probe motor cortical excitability during passive observation of a reaching-grasping action video.
• Delivered single TMS pulses synchronized with specific kinematic landmarks of the observed movement.
• Measured motor evoked potentials (MEPs) in the first dorsal interosseus (FDI) muscle.

Main Results:

• MEP amplitude in the FDI muscle was significantly modulated by the degree of finger aperture observed in the video.
• The modulation of MEPs correlated with specific temporal phases of the observed movement, linked to kinematic landmarks.

Conclusions:

• The findings support the existence of a mirror neuron system that links action execution and observation.
• Cortical motor output is temporally coded during action observation, mirroring the temporal dynamics of the observed action.