Motor resonance: Neurophysiological origin, functional role, and contribution of the motivational, moral, and social aspects of action

One of the most convincing results in support of embodied cognition is the evidence that when we observe another person performing an action, our sensorimotor system is acti- vated up to the muscular level as if we were performing that same action (Fadiga et al. 1995). Taking its cue from physical acoustics, this phenomenon has been named motor resonance. In the case of acoustic resonance, a vibrating tuning-fork will cause a second identical tuning-fork to vibrate at the same frequency. Similarly, numerous studies have demonstrated that motor resonance follows somatotopic principles and happens in a mus- cle-specific manner (Alaerts et al. 2009; Borroni and Baldissera 2008; Brighina et al. 2000; Clark et al. 2004; Fadiga et al. 1995; Urgesi et al. 2006), and that it is coupled to the movement phases (Alaerts et al. 2012; Borroni et al. 2005; Gangitano et al. 2001; Montagna et al. 2005). Given that this automatically induced sensorimotor representation of the per- ceived action corresponds to what is spontaneously generated during actual action execu- tion, the outcome of which would be known to the agent, embodied theories of cognition suggest that this motor replica may support action perception and understanding (Decety and Chaminade 2005; Gallese 2008, 2003; Keysers and Gazzola 2007). However, if the frequencies of the two tuning-forks differ, the acoustic resonance does not occur. It is suffi- cient to apply a clamp on the prongs of the second tuning-fork, thus changing the frequency of its oscillation, to interrupt the acoustic resonance phenomenon. Likewise, research described in this chapter shows how the clamp-like top-down influence of actor and observer intentions, values, and attitudes can affect motor resonance (Urgesi et al. 2020). The goal and, presumably, the final intention of the agent are cued by mapping other peo- ple’s actions onto one’s own sensorimotor representation, therefore motor resonance must necessarily encode additional information beyond the movement’s kinematics. For exam- ple, although a butcher understands exactly how to use a knife to slaughter a cow, this is not enough for him/her to resonate with another person using the same knife to inflict a deadly wound on a human being. The chapter will first describe the neurophysiological basis of motor resonance both in the monkey and in humans, then report evidence showing the role of sensorimotor activa- tion in others’ action perception and prediction. Finally, it will show research aimed at assessing which cognitive processes and neural mechanisms are involved in exerting a top-down modulation of motor resonance according to stimulus features, task require- ments, and actors’ and observers’ motivational states.