Empathy is a fundamental social ability affected in ASD and the broader autism phenotype. Empathic response is hypothesized to rely upon a neural perception-action mechanism in the mirror neuron system (MNS) that facilitates motor representation of observed actions and associated autonomic states, prompting affective sharing. Electroencephalography (EEG) studies indicate that MNS activity is indexed by suppression of oscillatory activity in the mu frequency range (8-13 Hz), which is sensitive to the social relevance of observed actions and correlates with trait empathy. Individuals with ASD demonstrate reduced mu suppression to observed actions of unfamiliar others, indicative of attenuated MNS response; consequent dysregulation of empathic response may contribute to difficulties in empathic drive, ability, and overall social function in ASD. Prior work has revealed MNS activity to observed physical pain in typical adults, but MNS response to observed social pain and its relation to autistic traits remains unexplored.
Objectives:
This study aimed to (a) investigate, for the first time, MNS activity elicited by observed social pain relative to observed physical pain and (b) elucidate the relationship between empathic response and autistic traits. We predicted greater MNS activity (as revealed by EEG mu suppression) to social pain than to physical pain due to the specific role of the MNS in social information processing. Autistic traits were hypothesized to correlate with reduced MNS activity, indicative of attenuated empathic response, to both social and physical pain, with greater reduction in the social pain condition.
Methods:
Participants were 44 typical adults prescreened for levels of subclinical autistic traits (Autism-Spectrum Quotient). EEG was recorded with a 128-electrode Hydrocel Geodesic Sensor net while participants viewed dynamic and static stimuli displaying hands in physically- and socially-painful and painless contexts. Participants viewed identical stimuli under two conditions, while performing an empathic task (rate distress) or a distractor task (count bracelets worn by actors). Mu power (8-13 Hz) was computed over central electrodes at C3 and C4 clusters, and log ratios (empathic attention:distractor condition) were contrasted for physical versus social situations.
Results:
Spectral analyses revealed comparable response in the high mu frequency range (11-13 Hz) to observed physical and social pain; however, mu suppression to painless social scenarios was greater than to painless physical scenarios (F(1,43)=7.90, p=.010). Autistic traits differentially modulated mu suppression to physical and social scenarios. Analyses in progress examine correlations between power in the theta (4-7 Hz) and alpha (8-13 Hz) frequency ranges during observed social and physical pain and autistic traits.
Conclusions:
Results indicated comparable MNS activation, as revealed by EEG mu attenuation, to observation of both physical and social pain in others; however, in painless conditions, only social scenarios elicited MNS activation. In the absence of salient pain cues, the MNS preferentially activates to social versus nonsocial actions, despite similar patterns of human movement. Subthreshold autistic symptomatology modulates this index of empathic response, demonstrating value as a metric for assessing social function and dysfunction in ASD.