Action perception and suboptimal motor performances: electrophysiological correlates

Objective: The activation of sensorimotor cortical structures can be enhanced by observing actions. Such cross-modal interaction is influenced by expertise, as shown by studies focused on complex expert gestures and on high-level motor proficiency. Conversely, the potential influence of familiarity with suboptimal motor performances on observers’ sensorimotor activation is still poorly explored, notwithstanding potential practical implications in clinical contexts. Following on a preliminary TMS study, we then devised an electrophysiological (EEG) investigation of processes supporting observation of complex actions performed by healthy individuals and patients affected by multiple sclerosis (MS). Participants and Methods: Twenty volunteers were asked to carefully observe videos depicting a healthy confederate, a minimally-impaired MS patient, a mildly-impaired MS patient, or a confederate trying to simulate mild motor difficulties who were performing a task tapping on fine motor abilities. EEG activity was recorded during the observation of videos. EEG frequency components were then extracted to analyse their modulation across conditions and video reiterations. Results: Data analysis highlighted globally lower beta power during the observation of patients’ videos with respect to confederate’s videos, even when he simulated poor motor performances. In addition, EEG activity in the beta range over somatosensory regions proved to gradually increase across videos reiterations, but only while participants observed the minimally-impaired patient’ performance. Conclusions: Findings suggest that even observation of suboptimal motor performances leads to a modulation of the activity of sensorimotor structures and corroborate the hypothesis that familiarity with peculiar kinematic patterns might modulate sensorimotor responses to observed actions, as if such suboptimal motor performances were progressively integrated into the individual repository of motor schemata.