P 38. Motor simulation coordinates joint actions in real time: Music performance meets on-line double-pulse TMS

Abstract

Question Joint action is grounded in the ability to integrate simultaneous self-and other-related behaviour in real time. We investigated whether this function is underpinned by motor simulation, i.e. the capacity to represent a perceived action in terms of the neural resources required to execute it (Jeannerod, 2000). This was tested in a music performance experiment wherein on-line brain stimulation (double-pulse Transcranial Magnetic Stimulation, dTMS) was employed to interfere with motor simulation. Methods Ten pianists (13.81±3.86years of musical training) played the right-hand part of piano pieces in synchrony with a recording of the left-hand part, which had (Trained) or had not (Untrained) been practiced beforehand. Training was assumed to enhance motor simulation of the audible left-hand part (cf. Haueisen and Knosche, 2001; D'Ausilio, 2006; Novembre, 2012). The task required adaptation to occasional tempo changes (i.e., accelerations or decelerations of large or small magnitude). In order to interfere with motor simulation processes, dTMS (two pulses, with an inter-onset-interval of 100ms and intensity at 110% of the individual's resting motor threshold) or sham was delivered over the right primary motor cortex prior to each tempo change. Tempo adaptation accuracy was quantified on the basis of the ratio between produced keystroke inter-onset intervals and target inter-onset intervals in recorded bassline parts (cf. Repp, 2005). Participant's perspective taking tendencies (i.e., how spontaneously they adopt others' perspectives) were assessed at the end of the experiment via an empathy questionnaire based on the Interpersonal Reactivity Index (Davis, 1980). Results Results indicated that dTMS impaired tempo adaptation accuracy only when pianists had practiced the left-hand bassline part beforehand, i.e., when motor simulation was presumably enhanced. This impairment, which was associated with a deceleration in the performance with respect to the audible bassline, occurred irrespective of tempo change direction (acceleration or deceleration) and magnitude (small or large). Finally, the decelerating effect of dTMS on performance tempo was greater in empathic individuals who possessed a stronger tendency to adopt others' perspectives (cf. Novembre, 2012). Conclusion These findings indicate that motor simulation provides a functional resource for the temporal coordination of one's own behaviour with others in dynamic social contexts.