Mu desynchronization during observation and execution of facial expressions in 30-month-old children

Abstract

Simulation theories propose that observing another’s facial expression activates sensorimotor representations involved in the execution of that expression, facilitating recognition processes. The mirror neuron system (MNS) is a potential mechanism underlying simulation of facial expressions, with like neural processes activated both during observation and performance. Research with monkeys and adult humans supports this proposal, but so far there have been no investigations of facial MNS activity early in human development. The current study used electroencephalography (EEG) to explore mu rhythm desynchronization, an index of MNS activity, in 30-month-old children as they observed videos of dynamic emotional and non-emotional facial expressions, as well as scrambled versions of the same videos. We found significant mu desynchronization in central regions during observation and execution of both emotional and non-emotional facial expressions, which was right-lateralized for emotional and bilateral for non-emotional expressions during observation. These findings support previous research suggesting movement simulation during observation of facial expressions, and are the first to provide evidence for sensorimotor activation during observation of facial expressions, consistent with a functioning facial MNS at an early stage of human development.

Mental Simulation of Facial Expressions: Mu Suppression to the Viewing of Dynamic Neutral Face Videos

“…Yet, mu suppression is reported to be modulated by contextual information, such as the actor's familiarity (Oberman et al, 2008) or their reward value (Gros et al, 2015), or gaming context in which the hand gestures are viewed (Perry et al, 2011). In addition, viewing facial gestures that do not suggest object interaction or deliberate action also seems to modulate mu rhythm (Moore & Franz, 2017;Moore et al, 2012;Rayson et al, 2016;Rayson et al, 2017). Thus, explanations which restrict mu suppression to voluntary or object-related actions are unlikely.…”

“…The ADFES is freely available for research from the Psychology Research Unit at the University of Amsterdam. Neutral faces were recorded by OK. Past research has validated mouth opening videos of actors as non-emotional (Rayson et al, 2016). Videos used in the present study were made similar to Rayson et al's (2016) and the ADFES stimuli in terms of duration, brightness, size, and contrast.…”

“…In contrast to findings which suggest a heightened sensitivity of the mu rhythm to emotional information, others found similar levels of mu modulation during gender discrimination and emotion recognition tasks which entailed viewing point-light displays of human figures' walk (Perry, Troje et al, 2010). Facial expressions have been used as stimuli in EEG mu suppression research only in a handful of studies (Cooper et al, 2013;Moore & Franz, 2017;Moore et al, 2012;Rayson et al, 2016;Rayson et al, 2017). Further research using different types of facial movements depicting varying levels of emotional information as the visual stimuli is necessary to investigate the differential sensitivity of the sensorimotor cortex to emotion-related information processing.…”

Increased sensorimotor activity during categorisation of ambiguous emotional expressions

“…Recent contributions to our understanding of emotion simulation have come from work exploring mu modulation during observation of different types of facial expressions. In a study in infants, Rayson et al (2016) found significant bilateral mu suppression for nonemotional expressions (mouth opening), but only right-hemispheric suppression for emotional (happy or sad) facial expressions. An emotion categorisation study from our group reported greater mu suppression while viewing dynamic videos of non-emotional facial movement (mouth opening) compared to non-biological movement (kaleidoscope pattern), but this was not observed for emotional faces (happy or sad) (Karakale et al, 2019).…”

Effects of age and sex on neurophysiological substrates of empathy: a cross-sectional EEG study

“…EEG objectively and non-invasively quantifies electrical cerebral activity timelocked to stimulus presentation. Emotional facial expressions are often used as stimuli to study socially complex skills, including empathy, as facial expressions powerfully communicate emotions to others in everyday life (Moore, Gorodnitsky, & Pineda, 2012;Rayson, Bonaiuto, Ferrari, & Murray, 2016). EEG were shown useful in demonstrating that the mere observation of emotional facial expressions elicits similar brain activation patterns than those involved in their expression (Rayson, et al, 2016).…”