Heartfelt Emotion: Heightened Sympathetic Arousal and Reduced Changes in Parasympathetic Arousal during Empathy for Pain in Autism
The ability to respond appropriately to social cues depends on autonomic flexibility – the capacity to regulate parasympathetic and sympathetic responses to stimuli. It has been proposed that autonomic dysregulation is a contributing pathway to reduced social reciprocity in autism spectrum disorder (ASD), and that parasympathetic regulation is reduced in ASD. However, most studies have focused on resting state arousal in ASD, and have not measured parasympathetic responses to social stimuli. Furthermore, the interaction between parasympathetic and sympathetic responses to social stimuli remains unexamined in ASD. In the case of empathy, it is thought that autonomic responses may either prime an individual for prosocial behaviour, or lead to feelings of personal distress, which are associated with reduced helping and consolation. Typically, heightened parasympathetic arousal and reduced sympathetic arousal to perceiving others’ pain are associated with greater empathic concern, increased prosocial behaviour and decreased distress. This pattern of autonomic arousal may be altered in ASD, impeding capacity for social engagement.
We investigated whether sympathetic and parasympathetic arousal during pain observation is correlated with amount of autism traits, as well as with subjective empathic concern and personal distress.
Individuals with varying levels of autism traits, as measured on the Autism Diagnostic Observation Schedule 2 and Autism-Spectrum Quotient, participated (N = 96, nASD = 27; ages 14 – 45). Participants watched two cycles of videos depicting facial pain. The stimuli featured male and female actors initially showing a neutral expression (1-3 s), followed by an expression of pain (3 s). We measured pre-ejection period (PEP) and skin conductance levels, indicators of sympathetic arousal, and respiratory sinus arrhythmia (RSA), a measure of parasympathetic arousal, over a 2-minute baseline period and during the videos. The autonomic measures were correlated with Likert-scale ratings of empathic concern for the actors and personal distress in response to the videos.
Pain observation elicited co-activation of the sympathetic and parasympathetic nervous systems to the first cycle of pain videos, followed by a synergistic decrease to resting state arousal levels. There was a significant interaction between amount of autism traits and video cycle in RSA, heart rate, and skin conductance: Participants with high amounts of autism traits had heightened sympathetic arousal (SCL) in cycle 1. Parasympathetic arousal (RSA) in cycle 1 was not associated with amount of autism traits. However, individuals with lower autism traits showed greater decreases in parasympathetic arousal from cycle 1 to cycle 2, indicating better regulation of arousal. PEP was not associated with amount of autism traits. Participants reported greater empathic concern than personal distress during pain observation. Empathic concern was not correlated with amount of autism traits.
The subjective and physiological data suggest that empathic concern for others’ distress is not diminished in ASD. However, reduced regulation of autonomic threat responses may contribute to reduced social reciprocity in ASD. The findings highlight the importance of including physiological and cognitive emotion regulation strategies in social interventions.