Corticospinal excitability during imagined and observed dynamic force production tasks: Effortfulness matters

Abstract

Research on motor imagery and action observation has become increasingly important in recent years particularly because of its potential benefits for movement rehabilitation and the optimization of athletic performance (Munzert et al., 2009). Motor execution, motor imagery, and action observation have been shown to rely largely on a similar neural network in motor and motor-related cortical areas (Jeannerod, 2001). Given that motor imagery is a covert stage of an action and its characteristics, it has been assumed that modifying the motor task in terms of, for example, effort will impact neural activity. With this background, the present study examined how different force requirements influence corticospinal excitability (CSE) and intracortical facilitation during motor imagery and action observation of a repetitive movement (dynamic force production). Participants were instructed to kinesthetically imagine or observe an abduction/adduction movement of the right index finger that differed in terms of force requirements. Trials were carried out with single- or paired-pulse transcranial magnetic stimulation. Surface electromyography was recorded from the first dorsal interosseous (FDI) and the abductor digiti minimi (ADM). As expected, results showed a significant main effect on mean peak-to-peak motor-evoked potential (MEP) amplitudes in FDI but no differences in MEP amplitudes in ADM muscle. Participants' mean peak-to-peak MEPs increased when the force requirements (movement effort) of the imagined or observed action were increased. This reveals an impact of the imagined and observed force requirements of repetitive movements on CSE. It is concluded that this effect might be due to stronger motor neuron recruitment for motor imagery and action observation with an additional load. That would imply that the modification of motor parameters in movements such as force requirements modulates CSE.

Subjective Vividness of Kinesthetic Motor Imagery Is Associated With the Similarity in Magnitude of Sensorimotor Event-Related Desynchronization Between Motor Execution and Motor Imagery

“…We found no significant difference in ERD KMI between 10% KMI and 40% KMI tasks. There are several studies investigating the association between imagined muscle contraction strength and corticospinal excitability ( Park and Li, 2011 ; Mizuguchi et al, 2013 ; Helm et al, 2015 ). In some of them, significant differences in motor-evoked potential amplitudes during KMI were observed in between low- and high-imagined contraction strength (i.e., 10 vs. 60% of maximal effort), suggesting difference in the corticospinal excitability depending on imagined contraction strength ( Mizuguchi et al, 2013 ; Helm et al, 2015 ).…”

Motor Imagery during Action Observation: A Brief Review of Evidence, Theory and Future Research Opportunities

“…It is important to note, however, that while the majority of evidence supports the effectiveness of MI and AO as independent instruction techniques, there is evidence to the contrary (see Braun et al, 2013; Gatti et al, 2013; Sarasso et al, 2015). Furthermore, it is difficult to draw clear conclusions on the mixed results provided across studies that have compared the potential advantages of motor imagery vs. action observation , both on motor function and neural processes (e.g., Porro et al, 2007; Filimon et al, 2007, 2015; Szameitat et al, 2012; Gatti et al, 2013; Gonzalez-Rosa et al, 2015; Helm et al, 2015). …”

A Systematic Investigation of the Effect of Action Observation Training and Motor Imagery Training on the Development of Mental Representation Structure and Skill Performance

“…Although motor imagery and action observation rely on a similar action representation, there is a difference between them in aspects of the mechanism of cognitive process. Motor imagery is a knowledge-driven cognitive process that is internally simulated based on information in long-term memory, without an external stimulus (e.g., Murphy, 1994 ; Soohoo et al, 2001 ; Holmes and Calmels, 2008 ; Helm et al, 2015 ). Instead, action observation is a percept-driven cognitive process that is externally guided by an external stimulus, such as a live demonstration or recorded video (e.g., Ram et al, 2007 ; Holmes and Calmels, 2008 ; Vogt et al, 2013 ).…”