Quasi-Movements and "Quasi-Quasi-Movements": Does Residual Muscle Activation Matter?

Area of Science:

• Neuroscience
• Motor Control
• Brain-Computer Interfaces

Background:

• Quasi-movements (QM) involve minimizing movement to avoid detectable muscle activation.
• QMs, like imaginary movements (IM) and overt movements, are associated with event-related desynchronization (ERD) in EEG sensorimotor rhythms.
• Previous studies noted stronger ERD in QMs than IMs, possibly due to undetected muscle activation in QMs.

Purpose of the Study:

• To re-examine the relationship between electromyography (EMG) signals and ERD in QMs using sensitive analysis.
• To differentiate the neural mechanisms underlying QMs and IMs.

Main Methods:

• Utilized sensitive data analysis procedures to detect subtle muscle activation.
• Compared EEG sensorimotor rhythm ERD and EMG signals during QMs, IMs, and a visual task.
• Correlated EMG findings with subjective estimates of movement.

Main Results:

• More trials with signs of muscle activation were found in QMs compared to a visual task and IMs.
• The rate of detected muscle activation in QMs did not correlate with subjective movement intensity.
• Contralateral ERD in QMs was stronger than in IMs, independent of EMG presence.

Conclusions:

• Brain mechanisms for QMs (strict sense) and 'quasi-quasi-movements' appear common but distinct from IMs.
• QMs offer potential for understanding motor action and developing brain-computer interfaces using attempted movements.