Abstract
Individuals with autism spectrum disorder (ASD) perform poorly in working memory (WM) tasks, with some literature suggesting that their impaired performance is modulated by WM load. While some neuroimaging and neurophysiological studies have reported altered functional connectivity during WM processing in individuals with autism, it remains largely unclear whether such alterations are moderated by WM load. The present study aimed to examine the effect of WM load on functional connectivity within the prefrontal cortex (PFC) in ASD using functional near-infrared spectroscopy (fNIRS). Twenty-two children with high-functioning ASD aged 8–12 years and 24 age-, intelligent quotient (IQ)-, sex- and handedness-matched typically developing (TD) children performed a number n-back task with three WM loads (0-back, 1-back, and 2-back). Hemodynamic changes in the bilateral lateral and medial PFC during task performance were monitored using a multichannel NIRS device. Children with ASD demonstrated slower reaction times, specifically during the “low load” condition, than TD children. In addition, the ASD and TD groups exhibited differential load-dependent functional connectivity changes in the lateral and medial PFC of the right but not the left hemisphere. These findings indicate that WM impairment in high-functioning ASD is paralleled by load-dependent alterations in right, but not left, intrahemispheric connectivity during WM processing in children with ASD. A disruption of functional neural connections that support different cognitive processes may underlie poor performance in WM tasks in ASD.
Highlights
Individuals with autism spectrum disorder (ASD) perform poorly in working memory (WM) tasks, with some literature suggesting that their impaired performance is modulated by WM load
A participant was included in the highfunctioning ASD group if he or she fulfilled the following criteria: (1) he or she had received a diagnosis of ASD based on the Diagnostic and Statistical Manual of Mental Disorders–5th Edition (DSM-5;1) from psychiatrists before the commencement of this study and scored above the cutoff points in all subscales in the Autism Diagnostic Interview-Revised (ADI-R;40) that was conducted by a registered clinical psychologist during the screening session for this study and (2) obtained a full-scale intelligent quotient (IQ) ≥ 80 on the Hong Kong version of the Wechsler Intelligence Scale for Children-Fourth Edition short form [WISC-IV (HK);41], which was administered by a clinical psychologist during the screening session
Independent-sample t-tests and chi-square tests showed that the typically developing (TD) and ASD groups did not significantly differ in age (p = .93), IQ (p = .22), sex (p = .20) or handedness (p = .086)
Summary
Individuals with autism spectrum disorder (ASD) perform poorly in working memory (WM) tasks, with some literature suggesting that their impaired performance is modulated by WM load. Coupling between frontal and parietal r egions[22] and between the left and right P FC23 increases during processing, which requires increased WM demand These studies provide evidence to support the notion that WM is mediated by the PFC and its distributed neural n etworks[24,25,26], which implies that good performance in a WM task requires an efficient flow of information between these brain areas to maintain and integrate information. Narita, S aotome[28] reported abnormal activation patterns in ASD adults over the left dorsolateral prefrontal cortex (PFC) during a visuospatial delayed recall task, a task reflecting participants’ WM capacity
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