Respiratory Sinus Arrhythmia and Facial Electromyography in Children with ASD

Background:  Previous research suggests that children with autism spectrum disorders (ASD) demonstrate lower respiratory sinus arrhythmia (RSA) at baseline compared to typically developing (TD) children (Bal et al., 2010; Ming et al., 2005; Van Hecke et al., 2009).  These findings indicate a mobilized physiological state that would be consistent with the frequently observed features of anxiety.  In addition, higher RSA has been related to better social skills ratings (Van Hecke et al., 2009) and faster emotion recognition (Bal et al., 2010) in children with ASD.  Facial expressions are major components of social interaction and communication, and individuals with ASD are known to have a limited range of facial expressions (APA, 1994).  However, the literature evaluating facial expressions using facial electromyography (EMG) in children with ASD has been limited, and the relationship between RSA patterns and EMG has not been explored.  

Objectives:  The current study explored the relation between facial EMG and RSA in children with ASD and TD children.  It was hypothesized that children with ASD would show different patterns of EMG activity and would be less reactive to presented affective expressions in comparison to TD children.  Further, it was expected that RSA would be positively related to emotional expressivity (i.e., children with higher RSA would show more EMG reactivity). 

Methods:  Seventeen children with ASD (M age =10.30 years, SD = 2.22) and 36 TD children (M age = 11.16 years, SD = 2.89) matched on age, sex, and IQ participated in the research.  Two minutes of baseline heart period (HP) data were collected.  Using the Dynamic Affect Recognition Evaluation (DARE; Porges, Cohn, Bal, & Lamb, 2007) software, participants were shown videos displaying a face starting with a neutral expression and slowly transitioning into one of the six emotions (i.e., anger, disgust, fear, happiness, sadness, surprise).  HP and facial EMG data over the corrugator supercilii (i.e., CS, eyebrow region) and zygomaticus major (i.e., ZM, cheek region) regions were collected continuously during the presentation using Biopac Systems.  HP data were edited with CardioEdit and RSA was calculated with CardioBatch (Brain-Body Center, University of Illinois at Chicago). 

Results:  Children with ASD had significantly lower baseline RSA than TD children (F (1,51) = 4.25, p = .045, previously published, see Bal et al., 2010).  Paralleling this group difference in RSA, preliminary analyses of the EMG data suggest that children with ASD were selectively more reactive in the ZM muscle region (i.e., lower face) than the CS muscle region (i.e., upper face), F (1, 12) = 6.650, p = .024.  Additional analyses are being conducted to expand the sample size and to evaluate possible emotion specific differences between the groups in EMG activity as well as correlations between EMG activity and RSA.

Conclusions:  Previous studies indicate a strong relationship between RSA and social skills, including emotion recognition, in children with ASD.  The current study extends previous research and explores the relationship between RSA and facial expressions measured by facial EMG.  Data continue to be analyzed.  Final results and future research directions will be discussed.