title: The neural correlates of visuo-spatial working memory in children with autism spectrum disorder: effects of cognitive load.
abstract: BACKGROUND
  Research on the neural bases of cognitive deficits in autism spectrum disorder (ASD) has shown that working memory (WM) difficulties are associated with abnormalities in the prefrontal cortex. However, cognitive load impacts these findings, and no studies have examined the relation between WM load and neural underpinnings in children with ASD. Thus, the current study determined the effects of cognitive load on WM, using a visuo-spatial WM capacity task in children with and without ASD with functional magnetic resonance imaging (fMRI).
  
  
  METHODS
  We used fMRI and a 1-back colour matching task (CMT) task with four levels of difficulty to compare the cortical activation patterns associated with WM in children (7-13 years old) with high functioning autism (N = 19) and matched controls (N = 17) across cognitive load.
  
  
  RESULTS
  Performance on CMT was comparable between groups, with the exception of one difficulty level. Using linear trend analyses, the control group showed increasing activation as a function of difficulty level in frontal and parietal lobes, particularly between the highest difficulty levels, and decreasing activation as a function of difficulty level in the posterior cingulate and medial frontal gyri. In contrast, children with ASD showed increasing activation only in posterior brain regions and decreasing activation in the posterior cingulate and medial frontal gyri, as a function of difficulty level. Significant differences were found in the precuneus, dorsolateral prefrontal cortex and medial premotor cortex, where control children showed greater positive linear relations between cortical activity and task difficulty level, particularly at the highest difficulty levels, but children with ASD did not show these trends.
  
  
  CONCLUSIONS
  Children with ASD showed differences in activation in the frontal and parietal lobes-both critical substrates for visuo-spatial WM. Our data suggest that children with ASD rely mainly on posterior brain regions associated with visual and lower level processing, whereas controls showed activity in frontal lobes related to the classic WM network. Findings will help guide future work by localizing areas of vulnerability to developmental disturbances.
authors: Diagnostic Imaging and Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.|Department of Applied Psychology and Human Development, Ontario Institute for Studies in Education, University of Toronto, Toronto, ON M5S 1V6, Canada.
authors: Vanessa M
authors: VM
authors: Vogan
authors: Diagnostic Imaging and Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
authors: Benjamin R
authors: BR
authors: Morgan
authors: Diagnostic Imaging and Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
authors: Wayne
authors: W
authors: Lee
authors: Diagnostic Imaging and Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
authors: Tamara L
authors: TL
authors: Powell
authors: Diagnostic Imaging and Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.|Department of Psychology, University of Toronto, Toronto, ON M5S 1V6, Canada.
authors: Mary Lou
authors: ML
authors: Smith
authors: Diagnostic Imaging and Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.|Department of Applied Psychology and Human Development, Ontario Institute for Studies in Education, University of Toronto, Toronto, ON M5S 1V6, Canada.|Department of Psychology, University of Toronto, Toronto, ON M5S 1V6, Canada.
authors: Margot J
authors: MJ
authors: Taylor
keywords: Autism spectrum disorder; Cognitive load; Executive function; Frontal lobe; Functional magnetic resonance imaging; Parietal lobe; Working memory