Differences in fNIRS-Based Cortical Activation Patterns between Children with and without Autism, during Object-Related Gestures.
Children with Autism Spectrum Disorder (ASD) have significant impairments in gestural performance including errors during tool use, pantomime, as well as meaningless actions. Children with ASD have more errors during meaningless gestures compared to tool use or pantomimed actions that involve a clear context (Smith & Bryson, 2007). Gestural impairments could be attributed to poor gesture perception, planning, or execution of motor programs/sequences required for gesture production (Dowell et al., 2009). Mirror Neuron Systems (MNS) in the inferior frontal gyrus (IFG), inferior parietal lobule (IPL), and superior temporal sulci (STS) play a role in the aforementioned processes when performing object-related gestures.
In the current study, we compared cortical activation in the MNS and sensori-motor regions during three naturalistic, object-related gestural tasks - object use, pantomime, meaningless.
14 children with ASD and 15 children without ASD between 6 and 16 years were seated at a table with a hammer and pegboard. The task was administered in a randomized, blocked fashion. Participants held a hammer and hit eight pegs on a pegboard in 3 different ways: a) Holds hammer: child hits pegs with an actual hammer, b) Pantomimes: child pretends to hammer, and c) Meaningless: the child taps the air. The oxy-hemoglobin response of the fNIRS signal was further analyzed to study differences in activation patterns between tasks, hemispheres, and the aforementioned regions of interest.
TD children showed greatest right MNS activation (IFG, STS, and IPL) in the Pantomime and Meaningless condition and both significantly differed from the Hammer condition; which had the lowest level of activation. There were no conditional differences in the left hemisphere. In contrast, children with ASD had fewer condition-based differences except for the right STS region wherein the pantomime condition led to greatest activation compared to both, meaningless and hammer conditions. In terms of group differences, TD children had greater bilateral STS activation whereas the children with ASD had greater right IFG and IPL activation than the TD group. In terms of lateralization, TD children had clear left lateralization in all MNS regions whereas the children with ASD showed bilateral activation except in the IFG in spite of the unilateral nature of the task.
Children with ASD showed reduced activation in bilateral STS regions; however, compensatory enhanced activation was seen in the right IFG and IPL regions. Pantomime and meaningless conditions led to greatest MNS activation in the TD children. In contrast, only pantomime led to higher activation in the children with ASD. Children with ASD also do not show clear left lateralization during unilateral gestures; which was clearly seen in the TD children. We may have identified neurobiomarkers of object-related gestures that could be used to explain gestural deficits and to develop contexts to facilitate gesture understanding/production in children with ASD.