Kick with the finger: symbolic actions shape motor cortex excitability

Abstract

A large body of research indicates that observing actions made by others is associated with corresponding motor facilitation of the observer's corticospinal system. However, it is still controversial whether this matching mechanism strictly reflects the kinematics of the observed action or its meaning. To test this issue, motor evoked potentials induced by single-pulse transcranial magnetic stimulation were recorded from hand and leg muscles while participants observed a symbolic action carried out with the index finger, but classically performed with the leg (i.e., a soccer penalty kick). A control condition in which participants observed a similar (but not symbolic) hand movement was also included. Results showed that motor facilitation occurs both in the observer's hand (first dorsal interosseous) and leg (quadriceps femoris) muscles. The present study provides evidence that both the kinematics and the symbolic value of an observed action are able to modulate motor cortex excitability. The human motor system is thus not only involved in mirroring observed actions but is also finely tuned to their symbolic value.

Action Observation and Effector Independency

“…In line with this latter observation, Senna et al (2014) showed that when participants viewed a typical hand action (grasping a pencil) performed by either a hand or a foot, hand motor evoked potentials (MEPs) increased not only during the observation of actions performed by the hand but also for grasping actions performed by the foot. This evidence confirms that motor activations by action observation occur in the muscles typically used to perform the observed action, even when the action is executed with another effector (see also Betti et al, 2015). This kind of ''hand'' template activation has also been shown in a study in which corticospinal excitability (CSE) of participants observing the opening and closing movements of the mouth and hand was measured (Finisguerra et al, 2015).…”

“…This consideration is supported by data from our post-experimental questionnaire in which participants scored the knee action as the least natural, probable and frequent to execute. Therefore, not only the goal of an action but also how the observed action is feasible and it is part of our behavioral repertoire that allows accessing motor templates (e.g., Buccino et al, 2004;Gazzola et al, 2007b;Betti et al, 2015). In addition, action plausibility based on the available context may guide our processing of others' actions.…”

Mindreading in the balance: adults' mediolateral leaning and anticipatory looking foretell others’ action preparation in a false-belief interactive task

“…Many studies show that there is selective discharge in motor activity according to the goal an action is directed towards, regardless of the specific effector used [7,39]. For example, adults observing someone wearing a miniaturized soccer shoe kicking a ball with the index finger showed motor facilitation in their leg [40]. There is broader evidence, then, that lends weight to our findings, suggesting that motor representation and processing of another's action towards an object is not just a matter of muscle, effector or posture specific resonance but, more importantly, of the belief-informed goal another's action is directed to.…”

Act on Numbers: Numerical Magnitude Influences Selection and Kinematics of Finger Movement

“…Participants wore a miniaturized soccer shoe and kicked a small ball with their right index finger. This specific type of action has recently been adopted to elicit cognitive processing and action planning ( Betti et al, 2015 ). In the present study, participants were instructed to kick the ball toward one of two identical little soccer goals, one located on their left and the other on their right, as soon as a stimulus was presented on a monitor screen.…”