Activation/Inhibition and Autism Versus Asperger Disorder

Background: The diagnosis of High Functioning Autism (HFA) versus Asperger’s Disorder (AD) is based on language impairment, but the utility and validity of this distinction remains controversial. Alternatively these subgroups may differ on the motivational continuum for approach versus avoidance behaviors regulated by the Behavioral Activation System (BAS) and the Behavioral Inhibition System (BIS). Specifically, we have raised the hypothesis that a predisposition to Behavioral Activation may lead individuals with Autism Spectrum Disorders (ASD) to engage in more interactions, be more active and effective in early language learning, be harder to diagnose early in life, and appear to fit an active-but-odd style described by Lorna Wing which is consistent with the clinical impressions of AD.  Alternatively, ASD children predisposed to Behavioral Inhibition may be more inhibited in interactions, passive and less effective in early language learning, withdrawn and easier to identify earlier in life, and appear to better fit the aloof prototype of Autism.

Objectives: To examine this hypothesis, the influence of BAS/BIS on the behavior of higher functioning 8 to 16 year-olds with ASD was assessed using anterior EEG asymmetry measures. Left Frontal Asymmetry (LFA) is associated with BAS and Right Frontal Asymmetry (RFA) is associated with BIS.  LFA- versus RFA-ASD children were expected to display significant differences on parent-report measures of global social communication impairment and indicators of pragmatic language. Children with LFA-HFA were also predicted to have later observed symptom onset than children with RFA.

Methods: EEG data were collected from 18 scalp sites for fifty-one ASD children. EEG asymmetry was computed for homologous frontal electrode pairs (e.g., lnF4-lnF3). Positive scores were indicative of relative LFA. Data on social communication impairment and symptom onset were collected via parent report on the Children’s Communication Checklist-Second Edition (CCC-2), and parent interview using the Autism Diagnostic Interview-Revised (ADI-R).

Results: Results indicated that parents of HFA children with LFA reported higher levels of general communicative competence on the CCC-2, GCC, F (3, 47) = 6.83, p = .01, but greater impairment on the CCC-2 scales of pragmatic communication when compared to RFA-HFA children, SIDC, F (3, 47) = 4.41, p < .05. Prior data suggests that this CCC-2 profile is common to AD.  Additional analyses indicated parents reported that the anterior asymmetry subgroups displayed different developmental courses of symptom onset on the ADI-R (“Age When Abnormality First Evident”) such that RFA was associated with early and more confident recognition of atypical (and stereotypically autistic) development, while LFA was associated with early, but less unambiguously autistic impairment, X² (51) = 3.75, p = .05.

Conclusions: This study demonstrates that anterior asymmetry subgroups are useful markers of phenotypic variability that may be meaningfully related to the course and expression of core symptoms of Autism. In particular, this study suggests that variability in measures of motivational predispositions to approach vs. avoidance behavior are associated with differences in early course and qualitative differences in communication impairment that have previously been associated with HFA versus AD diagnostic subgroups.