Neurological evaluation of the selection stage of metaphor comprehension in individuals with and without autism spectrum disorder

Abstract

Because of their difficulties with figurative language in conversation, it is commonly thought that individuals with autism spectrum disorder (ASD) do not understand figurative meaning. However, recent research indicates that individuals with and without ASD are similar in the first two stages of metaphor comprehension, up to and including successful generation of the figurative meaning. In the current study, we used a sentence decision task to evaluate the subsequent stage of metaphor comprehension, the selection stage, which requires suppression/inhibition of the unintended meaning as part of selecting the intended meaning. fMRI activation and functional connectivity were used to compare the selection stage of metaphor comprehension between high-functioning individuals with ASD and carefully matched controls. Cortical and subcortical regions of interest were selected based on the basal-ganglia model of cognitive control. Compared to controls, individuals with ASD recruited greater activation in regions related to verbal memory (thalamus), semantic associations (medial temporal gyrus), and basic visual processing (middle occipital gyrus). Functional connectivity analysis revealed fewer overall connections and cortical-subcortical connections in the ASD group compared to controls. There was a novel finding of maintenance of subcortical-subcortical connectivity in the ASD group, specific to the selection condition, despite differences in cortically involved connections. Reduced cortical-subcortical connectivity in the ASD group compared to controls may reflect a more global impairment in cognitive control pathways, while consistent subcortical-subcortical connectivity may reflect systemic inflexibility or preserved subcortical function and dissociation between subcortical and cortical systems. Further investigation is required.

Keywords: autism spectrum disorder; functional connectivity; graphical modeling; metaphor interference effect; spoken metaphor comprehension.