Respiratory Sinus Arrhythmia: A Marker of Positive Functioning In Children with Autism Spectrum Disorders

Background: Children with autism spectrum disorders (ASD) have difficulties modulating social behavior, including eye-to-eye gaze, vocalizations, and facial affect (American Psychiatric Association, 2000). Physiologically, children with ASD have less cardiac vagal tone relative to typically developing peers (Bal et al., 2010; Van Hecke et al., 2009). The Polyvagal Theory (e.g., Porges, 2007) suggests a neurobehavioral link between poor vagal regulation and social engagement deficits. The theory defines three neural circuits that provide adaptive responses to safe (social) interactions, danger, and life threat. These distinct pathways form a phylogenetically organized hierarchy with the most recent circuit supporting social communication involving a myelinated branch of the vagus and the striated muscles of the face and head.  This network can be monitored by quantifying respiratory sinus arrhythmia (RSA), a measure of myelinated vagal influence on the heart.  In ASD, low RSA has been related to function (e.g., Van Hecke et al., 2009) and problems with social engagement (Bal et al., 2010). We sought to replicate findings of RSA as a “marker” of positive social engagement in ASD and to extend this literature by examining the relationship between RSA and cognitive ability.  

Objectives: In accord with the Polyvagal Theory, we predicted higher RSA would be associated with increased joint attention and higher cognitive functioning, as measured by receptive vocabulary scores on the Peabody Picture Vocabulary Test (PPVT-III). 

Methods: Data were collected from 23 children (18 boys, 5 girls), aged 4 years 3 months to 7 years 9 months (M = 5.72, SD = 1.17) with prior diagnoses of Autistic Disorder (n = 12), Asperger’s Syndrome (n = 10), or Pervasive Developmental Disorder - Not Otherwise Specified (n  = 1). Heart period (HP) data were edited with CardioEdit and CardioBatch (Brain-Body Center, University of Illinois at Chicago; Porges, 1985). Data were analyzed to generate measures of RSA as a functional index of the myelinated vagus. Participants were administered the PPVT-III.  After, baseline HP data (i.e., for the RSA analyses) were collected during a neutral 3-minute video with the LifeShirt® heart monitor. Then, children engaged in 10 minutes of structured play tasks, using the Social Interaction Coding Scale (SICS; Bazhenova, 2006). Frequency of joint attention was coded from the SICS. 

Results: Higher RSA was significantly correlated with higher cognitive functioning (r = .44, p = .04) and increased joint attention (r = .48, p = .03). HP, however, did not show significant relationships with these measures (cognitive functioning: r = .36, p = .09; joint attention: r = .17, p = .47).  

Conclusions: Higher RSA was related to better social and cognitive functioning as assessed by increased joint attention and higher receptive vocabulary skills, but HP was not. This suggests that RSA, as an index of myelinated vagus activity and the functional competence of the Social Engagement Systems, provides a unique neurophysiological portal into social and cognitive functioning. The results provide further evidence that vagal regulation of the heart is a marker for positive social and cognitive functioning in children with ASD.