Quasi-Movements and “Quasi-Quasi-Movements”: Does Residual Muscle Activation Matter?

Abstract

Quasi-movements (QM) are observed when an individual minimizes a movement to an extent that no related muscle activation is detected. Likewise to imaginary movements (IM) and overt movements, QMs are accompanied by the event-related desynchronization (ERD) of EEG sensorimotor rhythms. Stronger ERD was observed under QMs compared to IMs in some studies. However, the difference could be caused by the remaining muscle activation in QMs that could escape detection. Here, we 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 QMs compared with a visual task and IMs. 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 QMs compared with IMs. These results suggest that brain mechanisms are common for QMs in the strict sense and “quasi-quasi-movements” (attempts to perform the same task accompanied by detectable EMG elevation) but differ between them and IMs. QMs 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.

Is there a continuum of agentive awareness across physical and mental actions? The case of quasi-movements

“…Although QM are learnt through reduction of movement amplitude to the point where the EMG response would become indiscernible by the experimenter, during the experimental sessions the participants were not always able to maintain the inhibition of EMG response. Nevertheless, as we showed in our previous paper (Vasilyev et al, 2023), mean RMS EMG values obtained in our experiment in the QM task were similar to values reported by Nikulin et al (2008).…”

“…For every QM and IM trial the 95th percentile of the corrected EMG RMS values (peekRMS) was used as an indicator of EMG amplitude. As we found in the previous publication (Vasilyev et al, 2023), EMG could not be observed in trials with peakRMS < 0.5 and could often be noticed in case of peakRMS > 0.5. Therefore, a value of 0.5 was chosen as the threshold for separating trails with low EMG and high EMG in that study, and we also used it in the current study.…”

“…Was this evidence directly available to the subjects, was feedback properly felt by them? When we analyzed the EEG data from the same experiment (Vasilyev et al, 2023), we found that a higher percentage of trails with elevated EMG did not lead to a stronger effect on the EEG sensorimotor rhythms (which are stronger in QM) and did not significantly affect statements about the reality of QM. Perhaps association of action reality with feedback holds for beliefs, but not for real muscle tension.…”

“…However, we understand that real instances of agentive awareness may or may not coincide with armchair intuitions. In order to correct these intuitions, we consider subjective reports of performing overt movements, quasi-movements, and kinesthetically imagined movements collected from the participants in our EEG study (Vasilyev et al, 2023). We chose to use freeform reports since QM is a poorly explored phenomenon.…”

“…Like in our previous paper (Vasilyev et al, 2023), here in the statistical analysis we used the peak values of corrected EMG RMS (see section 3.1 Material and methods), as they are more sensitive to fast muscle contractions. We examined the possible connection between the descriptors mentioned in sessions one and two and the percentage of trials with elevated EMG in the QM condition.…”