The neural representation of abstract concepts in typical and atypical cognition
Creators: name: Levinson, Hillary Jane
Publisher: name: No Publisher Supplied
Year: 2021

description: The ability to understand abstract concepts is one of the most impressive aspects of human cognition. However, abstract concepts are primarily defined by what they are not, leaving their study fragmented. Two factors that have proven useful in explaining neuroimaging data, but have not been applied to the neural representation of abstract semantics, are internal-to-self and external-to-self factors. Aim 1 of this dissertation determined the degree to which abstract concepts (as single words) align along internal and external factors, in behavioral (Study 1) and neural (Study 2) contexts. Study 1 demonstrated the validity of these factors as organizational dimensions for abstract concepts, and extended findings on the three factors (internal, external, concrete) underlying a feature-based semantic model. Neurally, Study 2 provided evidence for a 3-component space underlying semantic content based on the model used in Study 1; evidence for one of these dimensions relating to the internal factor was broadly supported.Aims 2 and 3 characterized abstract semantics in autism (ASD) (Studies 3-5). Using semantic regions for seed-based resting-state connectivity analysis, we identified differences within regions linked to concrete and abstract semantics between groups; specifically, we found a discontinuity of right superior anterior temporal lobe (ATL) connectivity along the superior temporal sulcus in ASD, where right ventral ATL connectivity overextended into the anterior portion of this region (Study 3). Aim 3 characterized abstract semantics in NT and ASD with a task-based study using phrases (Studies 4 &amp; 5). With phrases, we examined abstract semantics when it “goes wrong,” as can happen in ASD. Specifically, social and figurative content are two aspects of abstract language that can be sources of difficulty in ASD. By manipulating social and figurative factors in a single task, we characterized the neural correlates of each factor in both groups. We found evidence of concrete and perceptual processing for higher-order semantics in ASD, 1) at the whole-brain level: via thalamic engagement for processing figurative &gt; literal phrases, and 2) at the regional-level: via right vATL engagement for social &gt; nonsocial phrases in contrast to NT. We also identified group differences for literal phrase representation, with NTs showing greater neural correspondence than ASD for phrase features within the thalamus. The groups also displayed different neural responses to the features of social and nonsocial phrases, where the ASD group exhibited neural correspondence to the features of nonsocial phrases in the right supplementary motor area, while the NT group showed neural correspondence to the features of social phrases in the bilateral fusiform gyri. Overall, this research provides convergent behavioral and neural evidence for a semantic feature-based model of abstract concepts that emphasizes the importance of the internal/external-to-self distinction (Studies 1 &amp; 2). Finally, the studies in ASD provide evidence of reliance on concrete/perceptual processing for higher-order semantics, which informs pathways for future research into the neural mechanisms underlying symptomology, and possible targets for treatment.