ИСТИНА

Quasi-movements (QM) are observed when an individual minimizes a movement to an extent that no related muscle activation is detected. Likewise imaginary movements (IM) and overt movements, QM are accompanied by the event-related desynchronization (ERD) of EEG sensorimotor rhythms. Stronger ERD was observed under QM compared to IM in some studies. Based on these results and on the motor simulation theory, it was proposed that QM could be considered as a part of a continuum of activities, being positioned between IM and overt movements. However, the stronger ERD in QM compared to IM could be caused by the remaining muscle activation in QM that could escape detection. Here, we collected reports from participants who executed IM, QM and overt movements and re-examined the relation between the electromyography (EMG) signal and ERD in QM using sensitive data analysis procedures. More trials with signs of muscle activation were observed in QM compared to a visual task and IM. However, the rate of such trials was not correlated with subjective estimates of actual movement. Contralateral ERD did not depend on the EMG but still was stronger in QM compared to IM. These results suggest that brain mechanisms are common for QM in the strict sense and “quasi-quasi-movements” (attempts to perform the same task accompanied by detectable EMG elevation) but differ between them and IM. Moreover, we found a correlation between references to the sensation of muscle tension in QMs contrasted to IM and reports of the reality of QMs as actions. We conclude that the continuity assumption is likely false, at least for agentive awareness. In terms of awareness, QM roughly matches OM. Performing QM, one does intend to physically contract a muscle, and based on this effective component, one expects feedback, imagining it if the sensory evidence is inconclusive. QM could be helpful in research aimed at better understanding motor action and at modeling the use of attempted movements in the brain-computer interfaces with healthy participants.