Arousal Decrease in Sleeping Beauty: Audiences' Neurophysiological Correlates to Watching a Narrative Dance Performance of two-and-a-half hours

摘要

Watching dance is a multisensory experience. In dance, movements are intertwined with music and/or sound, costumes, the narrative, light and stage design. Recent studies have found neuroscientific evidence that a dance audience processes visual and auditory information, while mentally simulating and/or mirroring the movements. In other words, when spectators passively observe movements, their brain shows enhanced activity in areas that are also activated if they were executing the movements themselves. This paper presents an unusual exemplar of a scientific study in which motor simulation was measured in an emotionally and kinaesthetically loaded real life setting. The study illustrates two main points: 1) real-life conditions matter because they change the results and call into question the validity of laboratory based experimental conditions for research which is making claims about lived experience outside the laboratory and 2) new hypotheses emerged about the effects that the length of time spent watching dance can have on cortical excitability and action observation responses. The prevalent theory is that this mirroring process in action observation is automatic; however, it has been shown to increase with experience. It has been suggested that this mapping of observed movements onto one’s own motor system helps in understanding the intention of the actions. A lot of effort is being put into gaining further insight into the role the mirror neuron system and motor simulation play in emotion regulation. One way of measuring motor simulation is by externally stimulating the motor cortex, which leads to small muscular responses that can be recorded in the form of motor evoked potentials (MEPs). Changes in the size of MEPs are an indirect measure for the level of motor corticospinal excitability and are thus used to indicate the level of subjects motor mapping simulation’s in action observation. Even though the equipment to measure cortical excitability is mobile, most neuroscientific studies have been conducted in a laboratory setting that has little in common with real life – in particular a dance audience’s experience in the theatre. Here, we challenged this approach by measuring spectators’ brain responses in the theatre while they were watching a dress rehearsal of a commercial production of Sleeping Beauty, lasting 2.5 hours, performed by the Scottish Ballet. However high the ecological validity of this study, it is a small-scale exploratory and rather playful approach producing data that is not eligible for statistical hypothesis testing. Nevertheless, we provide a specific example of how the factors ‘time’ and ‘individuality’ can affect scientific results in artistic settings. We observed that the brain responses of our spectators in terms of cortical excitability decreased with time, were strongly individual, and did not conform to prevalent movement simulation hypotheses. The finding that motor simulation is not automatic during movement observation has important implications for the current understanding and research of mirror neuron activity. A contextual narrative may change the fronto-parietal mirror mechanism, which implies that previous findings based on controlled laboratory experiments could not automatically be transferred to real life. Interestingly though, the retrospectively reported emotional responses of one spectator partly matched his objective measures of cortical excitability attained during the dance performance. Hence, qualitative responses may be linked to quantitative responses more than one would expect, while laboratory findings may not be considered as substitutes for real life situations as previously assumed. However, this study simply highlights these points for future investigations. The observation of a decrease of cortical excitability over time could either indicate subjects’ adaptation to the procedure and the consequent effects of muscle relaxation; or changes in their emotional and cognitive engagement when watching dance. In either case, in line with research in dance studies that highlights the importance of time as a relevant factor in dance performance, this study shows that time is a relevant factor in measuring spectators’ responses to watching dance. This will require future attention.