Impaired Disengagement and its Relationship to Temperament in Infants at High Risk for ASD

Susan E. Bryson, PhD1, Nancy Garon, PhD2, Jessica Brian, PhD3, Isabel M. Smith1, Terry McCormick2, Wendy Roberts, MD4, Peter Szatmari5, and Lonnie Zwaigenbaum, MD6. (1) Dalhousie University, Halifax, NS B3K 6R8, Canada, (2) Autism Research Centre, IWK Health Centre, Halifax, NS, Canada, (3) Autism Research Unit, and Bloorview Research Institute, Hospital for Sick Children, and Bloorview Kids Rehab, 555 University Ave, Toronto, ON M5G 1X8, Canada, (4) Department of Pediatrics, Hospital for Sick Children & Bloorview Kids Rehab, University of Toronto, 555 University Avenue, Toronto, ON M5G 1X8, Canada, (5) Offord Centre for Child Studies, McMaster University, Hamilton, ON L8N 3Z5, Canada, (6) Department of Pediatrics, University of Alberta, Autism Research Centre, Glenrose Rehabitation Hospital, Edmonton, AB T5B 0B7, Canada

Background: Young children with ASD have difficulty disengaging visual attention from one of two competing stimuli (Landry & Bryson, 2004), but little is known about the early emergence or underlying mechanisms of this impairment.  

Objectives: To determine whether impaired disengagement distinguishes ASD in high-risk infants, and whether this impairment is associated with the Behavioural Approach dimension of temperament (Rothbart & Bates, 1998).

Methods: Participants were recruited from our prospective study of high-risk infants with an older sibling with ASD, and low-risk controls with no family history of ASD. Infants were assessed on a visual orienting paradigm at 6 and 12 months of age, and their parents completed the Infant Behavor Quesionnaire at 12 months. An independent diagnositc assessment for ASD was conducted at 36 months of age, yielding 3 groups: ASD sibs (n=14), non-ASD sibs (n=43) and controls (n=44).

Results: A repeated measures ANOVA conducted on reaction times (RTs) to disengage and shift attention revealed a significant Group X Attention Condition X Side interaction, F(2, 98)=3.77, p<.03. At 12 (vs. 6) months, infants who were subsequently diagnosed with ASD were distinguished from non-ASD sibs and controls by significantly longer disengage RTs on the left than on the right side of space. No significant left-right RT differences were found for either the non-ASD sibs or controls. Left-right asymmetries in disengaging visual attention were significantly related to low Behavioural Approach in both the ASD sibs (r=.49, p=.06) and non-ASD sibs (r=.41, p=.003).  

Conclusions: Our finding that asymmetries in disengaging attention distinguish ASD at 12 but not 6 months implicates dysfunction of frontal or executive control of attention (Johnson, 1996). This asymmetry, and its relationship to low Behavioural Approach, is consistent with evidence of right cortical asymmetry in a subgroup with ASD (Mundly et al., 2007; Sutton et al., 2005).


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