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Hippocampal-Parietal Hyper-Connectivity Predicts Visual-Spatial Abilities in Children with Autism
Autism spectrum disorders (ASDs) are often accompanied by an uneven profile of cognitive capacities. From rare reports of savant skills to the consistent finding of stronger performance than verbal IQ, spared and enhanced abilities in autism tend to involve veridical memory and visual-spatial processing. While little is known regarding the neural underpinnings of enhanced abilities in children with autism, these areas of strength point towards the involvement of medial temporal and parietal lobe structures. Resting state functional MRI provides a powerful method for probing intrinsic connectivity between brain regions. Recent studies using the method have revealed a conflicting picture of both hypo- and hyper-connectivity in individuals with ASD relative to typically developing (TD) peers.
Objectives:
We sought to understand whether patterns of intrinsic functional brain connectivity in children with ASD could be related to cognitive strengths. We focused on connectivity of the hippocampus, an area critically involved in memory and spatial navigation.
Methods:
Six minutes of resting state functional MRI was collected in 20 children (aged 7-12) with ASD and 19 TD children, matched on age, IQ, and gender. We compared functional connectivity between groups from left and right anterior hippocampal seeds, an area implicated in binding multiple visual-spatial features. Parent report of exceptional abilities from the ADI-R were used to compare connectivity measures amongst children with ASD. Support vector regression (SVR) was used to probe whether areas differing in hippocampal connectivity could predict verbal IQ (VIQ) and performance IQ (PIQ) in TD children and children with ASD.
Results:
Children with ASD displayed patterns of both hypo- and hyper-connectivity of the hippocampus with other cortical and subcortical regions. TD children had greater connectivity of the hippocampus to the posterior cingulate, ventral medial prefrontal cortex and parahippocampal gyrus, all areas implicated in the default mode network and self-related processing. In contrast, children with ASD had greater connectivity from right hippocampus to the right intraparietal sulcus and the adjoining angular gyrus, areas implicated in visual-spatial processing. Hippocampal-parietal connectivity was strongest in children with ASD whose parents reported they had exceptional visual-spatial abilities. SVR analyses revealed that the pattern of hippocampal connectivity in this parietal cluster could predict PIQ scores for children with ASD but not for TD children. Hippocampal-parietal connectivity did not predict VIQ for either group.
Conclusions:
These results suggest that hippocampal-parietal hyper-connectivity in children with ASD is related to spared and enhanced non-verbal intelligence and visual spatial abilities in these children.