Neurophysiological investigation of auditory augmentation to facilitate observational learning of everyday actions

Abstract

This thesis explores the neurophysiology of auditory augmentation of observed actions, and its effects on motor learning, neural activity, and plasticity. To this end, three studies were conducted. In the first study, we used Transcranial Magnetic Stimulation (TMS) to determine the effects of practising a motor task via sonification of combined action observation and motor imagery (sAOMI) on corticospinal excitability, compared to practising without extrinsic auditory information. In addition, we aimed at probing practice-dependent audiomotor plasticity. To this extent we used a variation of a commonly used method to probe and induce plasticity in humans, auditory paired associative stimulation (aPAS). Practice significantly increased corticospinal excitability, but sonification did not affect it. In addition, while aPAS completed alone significantly modulated corticospinal excitability, when practice primed aPAS, no neuromodulation was found. In a follow-up study, we explored the effects of sAOMI on corticospinal excitability during action observation (AO) or AOMI of the same action, and whether sonification induced audiomotor resonance, which is usually interpreted as development of an audiomotor association. The results corroborated and extended the findings of the previous study: practice increased corticospinal excitability at rest and during AO and AOMI, but sonification did not affect it. In addition, with sonification did not induce an audiomotor association. In a third study, we used electroencephalography (EEG) and other psychophysical measures, including a motor imagery questionnaire and mental chronometry, to assess changes resulting from practising with sonified action observation, followed by motor imagery of the same action. After two practice sessions, performance and kinaesthetic motor imagery vividness significantly improved, and participants’ mental chronometry was significantly more aligned with the speed of the observed action, compared to pre-practice measures. Sonification did not induce changes in any measure. EEG analysis revealed that participants who practised with sonification were able to sustain event-related desynchronization (ERD) in the lower alpha band (7-10 Hz) for longer, compared to participants who practices without sonification. No changes in higher alpha (10-12 Hz) or Beta (16-25 Hz) bands were found. Taken together, convergent results from this thesis suggest that sonified action observation has little effect on neurophysiological and behavioural markers of motor imagery ability and performance in healthy individuals. On the other hand, practising with sonified action observation may induce attentional modulations that enhance the learner’s ability to sustain action-related attentional processing for longer. We discuss these results in the context of contemporary neurocomputational theories of perception and action.