Abstract
Working memory (WM) impairments may contribute to the profound behavioural manifestations in children with autism spectrum disorder (ASD). However, previous behavioural results are discrepant as are the few functional magnetic resonance imaging (fMRI) results collected in adults and adolescents with ASD. Here we investigate the precise temporal dynamics of WM-related brain activity using magnetoencephalography (MEG) in 20 children with ASD and matched controls during an n-back WM task across different load levels (1-back vs 2-back). Although behavioural results were similar between ASD and typically developing (TD) children, the between-group comparison performed on functional brain activity showed atypical WM-related brain processes in children with ASD compared with TD children. These atypical responses were observed in the ASD group from 200 to 600 ms post stimulus in both the low- (1-back) and high- (2-back) memory load conditions. During the 1-back condition, children with ASD showed reduced WM-related activations in the right hippocampus and the cingulate gyrus compared with TD children who showed more activation in the left dorso-lateral prefrontal cortex and the insulae. In the 2-back condition, children with ASD showed less activity in the left insula and midcingulate gyrus and more activity in the left precuneus than TD children. In addition, reduced activity in the anterior cingulate cortex was correlated with symptom severity in children with ASD. Thus, this MEG study identified the precise timing and sources of atypical WM-related activity in frontal, temporal and parietal regions in children with ASD. The potential impacts of such atypicalities on social deficits of autism are discussed.
Highlights
Autism spectrum disorder (ASD) is a severe neurodevelopmental disorder characterized by striking impairments in social interaction and the presence of circumscribed interests and stereotypedrepetitive behaviours.[1]
Accuracy scores (Acc), mean reaction times (RTs) and RT coefficient of variation (CV) associated with the target stimuli were recorded in each n-back condition, and ‘repeat–correct’ trials (RC) were compared between groups with repeated measures analysis of variance to ensure adequate quality of behavioural results prior to source analysis
We found a significant main effect of condition (1- and 2-back) for all three behavioural measures, Acc, RTs and RT CV (Acc: F (1,38) = 136.08; RTs: F(1,38) = 138.58 and CV: F(1,38) = 17.16; all P's o0.0002) but no effect of the group and no interaction between the factors
Summary
Autism spectrum disorder (ASD) is a severe neurodevelopmental disorder characterized by striking impairments in social interaction and the presence of circumscribed interests and stereotypedrepetitive behaviours.[1]. Likewise, reduced recruitment of the right posterior temporal regions[22] in addition to reduced prefrontal activity[21,22] was identified in adults with ASD using two versions of the nback task These atypicalities involved brain areas known to have a crucial role in WM processes. 0.97 0.06 0.28 0.63 information in WM,[27,28] the inferior parietal lobe activity has been associated with an information buffer function[21] and is associated with improved WM ability in healthy children.[29,30,31,32] These results suggest impairments in core WM processes yet compensatory strategies that allow, in the majority of cases, normative performance on specific WM memory tasks. We used MEG recordings during an n-back task to compare WM-related brain activity across different complexity levels (1-back vs 2-back) between children with highfunctioning ASD and age-matched controls
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