Examining Relations between Cardiac Autonomic Activity and Autism Traits in Adults

Background: The autonomic nervous system (ANS) regulates basic bodily responses, and individuals with ASD show atypical cardiac ANS activity, including higher heart rate (HR) and lower variation in timing between heart beats during respiration, known as respiratory sinus arrhythmia (RSA; Bal et al., 2010). In neurotypical adults, cardiac ANS activity is related to emotion processing, with greater HR deceleration when viewing negative images as compared to positive and neutral (Bradley et al., 2008), and RSA positively correlating with emotion recognition (Quintina et al., 2012). Relatedly, RSA has been found to positively correlate with social functioning in ASD (Van Hecke et al., 2009). Recent work found that pupillary ANS activity was related to ASD traits in a broad population of children (DiCriscio & Troiani, 2017), but more work is needed to understand how variability in cardiac ANS responses might also relate to ASD traits.

Objectives: This study investigated cardiac ANS activity during emotional images and ASD traits in adults.

Methods: Participants included 42 college students who viewed 60 emotionally-valenced images for six seconds per image (20 neutral, 20 negative, and 20 positive, from the International Affective Picture System; Lang et al., 2005). HR was recorded using a Biopac MP150WSW system. Participants then completed the Social Responsiveness Scale, Second Edition (SRS-2; Constantino & Gruber, 2012), a measure that has been used to assess ASD traits in the broader population (e.g., DiCriscio & Troiani, 2017). Total SRS-2 scores ranged from 19 to 107 (M = 50.76, SD = 18.16). 𝜟HR was calculated as HR during the image minus HR during a 2-second pre-image baseline, and average 𝜟HR was computed for each valence. A negative bias score was calculated as 𝜟HR to negative images minus average 𝜟HR to neutral and positive. RSA was averaged across the first five 60-second segments of the valence task using a respiration frequency of 0.12-0.40 Hz.

Results: An ANOVA examined effects of valence on 𝜟HR and found a significant effect, F(2,82) = 3.865, p = .025 (see Figure 1), with greater HR deceleration to negative images as compared to positive and neutral (ps < .05). Associations between cardiac ANS activity (RSA, 𝜟HR to negative, and HR negative bias) and SRS-2 Total score were examined, and no significant correlations were found (ps > .20). Results remained unchanged with and without the 12 participants with SRS-2 scores in a range typically associated with ASD (T-score > 59).

Conclusions: Consistent with prior work by Bradley et al. (2008), we found greatest HR deceleration to negative images. However, unlike work with individuals with ASD (e.g., Van Hecke et al., 2009), there were no correlations found between cardiac ANS activity and autism-related traits. This might suggest that differences in cardiac ANS vary with ASD characteristics only in individuals meeting clinical criteria for ASD, in contrast to pupillary ANS responses. More work is needed to understand why different aspects of ANS functioning might vary with ASD traits in individuals with ASD specifically, as opposed to varying with these traits in the broader population.