Objectives: To determine if young children with autism show diminished VT at rest in comparison to non-autistic children, and to determine if these groups differ in their profile of responses to social challenges of varying intensity. We also sought to examine the relations between VT and measures of social and adaptive behaviors.
Methods: Children with Autistic Disorder (AUT; n = 15) and children without autism (nonAUT; n = 8) were group matched on chronological age and nonverbal IQ (2 ½ - 6 ½ years of age). Cognitive abilities were assessed with the Differential Ability Scales or the Bayley Scales of Infant Development. Diagnoses were confirmed with the Autism Diagnostic Observation Schedule. Social and adaptive behaviors were assessed with the Vineland Adaptive Behavior Scales. Children were observed during a baseline period and then during a series of social events, including feigned distress reactions by a female examiner, and a stranger approach procedure. ECG was acquired during this behavioral assay. Automated algorithms were utilized to detect and correct for potential artifact in the ECG signal, and VT was calculated from the resulting ECG time series. Children were categorized as showing reductions in VT from baseline to challenge conditions (“responders”) or showing increases or no change in VT (“non-responders”).
Results: Groups did not differ in baseline VT or in changes in VT during social challenge. Within group analyses were conducted to compare VT responders to non-responders on measures of social and adaptive abilities (Vineland Scales). For less intrusive social conditions, responders and non-responders did not differ on Vineland adaptive behavior scores. However, for the intrusive stranger approach condition, AUT group responders showed higher mean scores on Socialization Domain than non-responders (T [10.5], p = 0.02). Group differences on the Vineland Daily Living Skills, Communication, and Motor Skills domains were not statistically significant. Within the nonAUT group, there were no statistically significant differences between responders and non-responders on Vineland Scale domain scores.
Conclusions: These results suggest that children with autism may show different patterns of parasympathetic responses to social events of varying degrees of intensity, and the individual differences in these physiologic responses are predictive of social functioning, as measured by parent report. These results will be discussed in relation to possible differences in response thresholds and implications for understanding the impact of regulatory capacity on behavioral functioning in young children with autism