Modulation of EMG power spectrum frequency during motor imagery

Abstract

To provide evidence that motor imagery (MI) is accompanied by improvement of intramuscular conduction velocity (CV), we investigated surface electromyographic (EMG) activity of 3 muscles during the elbow flexion/extension. Thirty right-handed participants were asked to lift or to imagine lifting a weighted dumbbell under 3 types of muscular contractions, i.e. concentric, isometric and eccentric, taken as independent variables. The EMG activity of the agonist (long and short head of biceps brachii) and the antagonist (long portion of triceps brachii) muscles was recorded and processed to determine the median frequency (MF) of EMG power spectrum as dependant variable. The MF was significantly higher during the MI sessions than during the resting condition while the participants remained strictly motionless. Moreover, the MF during imagined concentric contraction was significantly higher than during the eccentric. Thus, the MF variation was correlated to the type of contraction the muscle produced. During MI, the EMG patterns corresponding to each type of muscle contraction remained comparable to those observed during actual movement.In conclusion, specific motor programming is hypothesized to be performed as a function of muscle contraction type during MI.

Lateralization patterns of covert but not overt movements change with age: An EEG neurofeedback study

“…Although increased EMG activity during MI has been reported in several studies (Gandevia, Wilson, Inglis, & Burke, 1997;Guillot et al, 2007;Guillot, Di Rienzo, MacIntyre, Moran, & Collet, 2012;Lebon, Rouffet, Collet, & Guillot, 2008), it has not been demonstrated yet that increased EMG activity is related to performance enhancement (Guillot et al, 2012). While the two strategies MI and QM did not differ in the amount of residual movements, more trials had to be excluded in the elderly compared to young adults.…”

Body posture modulates imagined arm movements and responds to them

“…The execution of postural actions apparently in support of imagined arm movements is worthy of detailed investigation because it may help clarify the mechanisms that allow humans to assemble and simulate motor coordinations without physically executing the corresponding movements. Imagined movements resemble physical ones not only in retaining kinematic and biomechanical constraints but also in incorporating afferent signals regarding the relevant limbs' postural status (as in De Lange et al 2006) and in generating efferent signals resulting in task-specific but level-attenuated EMG activity in the involved muscles (Guillot et al 2007;Lebon et al 2008). Jeannerod (2006) suggested that motor execution is prevented during imagery by an inhibition mechanism that operates at the brain stem or spinal level.…”

“…ated EMG activity in the involved muscles (Guillot et al 2007; Lebon et al 2008). Also, corticospinal or cerebral activation during motor imagery can be modulated by changes in afferent signals, for example, by immobilizing a limb (Kaneko et al 2003), or by a limb posture that is incompatible with the imagined action (De Lange et al 2006;Vargas et al 2004).…”

Incomplete inhibition of central postural commands during manual motor imagery

“…According to the simulation hypothesis, these similarities suggest that motor imagery involves a sequence of neural events similar to motor execution, except that an inhibition mechanism operates downstream along the efferent pathway, possibly at the brainstem or spinal level, to suppress overt movement (Bonnet et al, 1997;Jeannerod, 2006). If such an inhibition mechanism exists, it must be incomplete (Jeannerod, 1994), because motor imagery has been shown to produce subliminal EMG activity in the involved muscles (Guillot et al, 2007;Lebon et al, 2008), as well as tonic and phasic autonomic responses preparing the body for action (Calabrese et al, 2004;Collet et al 2013;Collet and Guillot, 2009;Decety et al 1991).…”