Abstract
A small corpus callosum (CC) is one of the most replicated neurobiological findings in autism spectrum (AS). However, its effect on interhemispheric (IH) communication is unknown. We combined structural (CC area and DWI), functional (task-related fMRI activation and connectivity analyses) as well as behavioral (Poffenberger and Purdue tasks) measures to investigate IH integration in adult AS individuals of typical intelligence. Despite similar behavioral IH transfer time and performances in bimanual tasks, the CC sub-regions connecting frontal and parietal cortical areas were smaller in AS than in non-AS individuals, while those connecting visual regions were similar. The activation of visual areas was lower in AS than in non-AS individuals during the presentation of visual stimuli. Behavioral IH performances were related to the properties of CC subregions connecting motor areas in non-AS individuals, but to the properties of posterior CC regions in AS individuals. Furthermore, there was greater functional connectivity between visual areas in the AS than in the non-AS group. Levels of connectivity were also stronger in visual than in motor regions in the autistic subjects, while the opposite was true for the non-autistic group. Thus, visual IH transfer plays an important role in visuo-motor tasks in AS individuals. These findings extend the well established enhanced role of perception in autistic cognition to visuo-motor IH information transfer.
Highlights
The observation that the corpus callosum (CC) is smaller in autism spectrum (AS) individuals than in non-AS individuals is among the most replicated neurobiological findings in AS
The aim of this study was to establish whether the alterations of the size of the CC observed in AS affect IH transfer, and whether the cortical areas involved in IH information transfer differ in AS and non-AS individuals
When FSIQ was included in the model as a covariate, it had a significant effect on the Crossed–Uncrossed Difference (CUD) measure
Summary
The observation that the corpus callosum (CC) is smaller in autism spectrum (AS) individuals than in non-AS individuals is among the most replicated neurobiological findings in AS. Investigations examining alterations of functional connectivity in AS individuals found evidence of low intrahemispheric, fronto-posterior long-distance connectivity (Schipul et al, 2011; Uddin et al, 2013; Vissers et al, 2012), associated with short distance (or local) over-connectivity (Just et al, 2004; Just et al, 2007) Recent reconsideration of these findings emphasizes the dependence on the methodology used of conclusions drawn from functional connectivity (Muller et al, 2011) and anatomical CC (Lefebvre et al, 2014) investigations in AS populations. Besides alterations of CC volume, alterations of intrahemispheric frontal, temporal and parietal white matter volume (Amaral et al, 2008; Anagnostou and Taylor, 2011; Just et al, 2012) and diffusion properties (Aoki et al, 2013; Travers et al, 2012; Vissers et al, 2012) suggest that widespread alterations of connectivity occur in AS
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