Abstract
Motor resonance (MR) can be influenced by individual differences and similarity in the physical appearance between the actor and observer. Recently, we reported that action simulation is modulated by an implicit visual sensitivity towards normal-weight compared with overweight bodies. Furthermore, recent research has suggested the existence of an action observation network responsible for MR, with limited evidence whether the primary motor cortex (M1) is part of this. We expanded our previous findings with regards to the role of an implicit normal-weight-body preference in the MR mechanism. At the same time, we tested the functional relevance of M1 to MR, by using a transcranial direct current stimulation (tDCS) protocol. Seventeen normal-weight and 17 overweight participants were asked to observe normal-weight or overweight actors reaching and grasping a light or heavy cube, and then, at the end of each video-clip to indicate the correct cube weight. Before the task, all participants received 15 min of sham or cathodal tDCS over the left M1. Measures of anti-fat attitudes were also collected. During sham tDCS, all participants were better in simulating the actions performed by normal-weight compared with overweight models. Surprisingly, cathodal tDCS selectively improved the ability in the overweight group to simulate actions performed by the overweight models. This effect was not associated with scores of fat phobic attitudes or implicit anti-fat bias. Our findings are discussed in the context of relevance of M1 to MR and its social modulation by anti-fat attitudes.
Highlights
Mounting research evidence indicates that the observation of one person performing an action can automatically activate a network of cortical brain regions in the observer associated with action execution
It has been recently shown that motor resonance” (MR) can be modulated by one’s experience with the observed action (Abreu et al, 2012; Buccino et al, 2004), whereas physical and psychological similarities between the actor and observer can influence the level of action simulation and anticipatory representation of other’s actions (Avenanti, Sirigu, & Aglioti, 2010; Azevedo, Macaluso, Viola, Sani, & Aglioti, 2014; Cazzato & Makris, 2019; Obhi, Hogeveen, Giacomin, & Jordan, 2014)
We investigated how inhibitory versus control noninvasive brain stimulation over the left primary motor cortex (M1) can modulate the simulation and understanding of observed familiar actions in terms of a weight discrimination task
Summary
Mounting research evidence indicates that the observation of one person performing an action can automatically activate a network of cortical brain regions in the observer associated with action execution This phenomenon is known as “motor resonance” (MR), and it is considered a critical element of one’s ability to anticipate forthcoming actions and make predictions about their outcome (Aglioti, Cesari, Romani, & Urgesi, 2008; Fadiga, Fogassi, Pavesi, & Rizzolatti, 1995; Urgesi et al, 2010). It has been recently shown that MR can be modulated by one’s experience with the observed action (Abreu et al, 2012; Buccino et al, 2004), whereas physical and psychological similarities between the actor and observer can influence the level of action simulation and anticipatory representation of other’s actions (Avenanti, Sirigu, & Aglioti, 2010; Azevedo, Macaluso, Viola, Sani, & Aglioti, 2014; Cazzato & Makris, 2019; Obhi, Hogeveen, Giacomin, & Jordan, 2014). We have shown that MR can be modulated by differences in the body weight between the actor and observer and that
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