Neural, Behavioral and Parent-Reported Indices of Executive Attention in Younger Siblings of Children with Autism
Younger siblings of children with autism (High-risk [HR]-Siblings) are at increased risk for autism or subclinical social/cognitive deficits referred to as the Broader Autism Phenotype (BAP). Though much research has described behavioral variability exhibited by HR-siblings, little is known about neural mechanisms associated with this heterogeneity. Executive attention is the ability to monitor and resolve conflict between competing stimuli, and is related to self-regulation and social skills. Deficits in executive attention may account for the regulatory and social deficits observed in HR-Siblings.
This study uses a multi-measure approach (EEG, Flanker Task, parent-report) to examine executive attention in preschool-aged HR-Siblings (both affected and unaffected) and a comparison group of low-risk siblings of children without autism (LR-Siblings).
Participants include 22 4-7 year-old younger siblings of children with an autism spectrum disorder diagnosis, 3 of whom displayed clinically-significant symptoms of autism (Affected HR-Siblings), and an age-, gender,- and sex-matched sample of 16 LR-Siblings. Participants successfully (≥40% accuracy) completed the Children’s Attention Network Task (ANT; Rueda, 2004), with electroencephalograph (EEG) collected simultaneously. In this modified Flanker task children pressed a button corresponding to a central stimulus’ direction. Central stimuli faced the same (congruent, CON) or opposite (incongruent, ICON) direction as flanking stimuli. CON and ICON stimulus-locked event related potentials (ERPs; N200, P300) were examined at fronto-central sites. Behavioral variables include reaction time and accuracy to CON and ICON stimuli. Parents reported on children’s effortful control (Child Behavior Questionnaire, CBQ; Rothbart et al., 2001).
A series of repeated measures analyses of variance (Group : Affected HR-Siblings, Unaffected HR-Siblings, LR-Siblings X Trial Type : CON vs ICON) were conducted with task accuracy and reaction times (behavioral), and N200 adaptive mean amplitude at Fz (neurophysiological) as the dependent variables. Behaviorally, a main effect of trial type revealed that regardless of diagnostic group, participants made more errors F(1,36)=32.36, p<.001, and responded more slowly F(1,36)=7.97, p=.008, on incongruent compared to congruent trials. Neurophysiologically, a main effect of group emerged, F(2, 28)=6.76, p=.004, with Affected HR-Siblings exhibiting significantly less negative N200 adaptive means than LR-Siblings regardless of condition, Mdif=7.54, p=.005 (Figure 1). With respect to parent-reported Effortful Control, a multivariate analysis of variance revealed group differences in global levels of Effortful Control, F(8, 46)=4.03, p=.001, driven by differences in Inhibitory Control, F(2, 26)=6.76, p=.004. Affected HR-Siblings were rated highest in Inhibitory Control (Figure 2). Across the full sample, and split by group, the N200 ERP was not correlated with task performance or parental reports of effortful control.
Despite a lack of differences in behavioral performance between HR- and LR-Siblings, a neurophysiological index (N200) clearly differentiated sibling groups. These impairments fell along a continuum from Affected HR-Siblings to LR-siblings, indicative of a BAP. Interestingly, Affected HR-Siblings exhibited higher Inhibitory Control than LR-Siblings. These children may be overly controlled and rigid in their thinking, which may serve as a compensatory mechanism in ANT task performance, where groups performed comparably. Subtle differences in cognitive and executive attention may index the BAP better than behavioral measures alone.