Poster B21, Tuesday, August 20, 2019, 3:15 – 5:00 pm, Restaurant Hall
Neural mechanisms of generalization for language learning in autism spectrum disorder
Brian Castelluccio1, Allison Canfield2, Inge-Marie Eigsti3;1Alpert Medical School of Brown University, 2University of Rochester Medical Center, 3University of Connecticut
Introduction: The structural linguistic abilities of people with autism spectrum disorder (ASD) vary substantially, ranging from the minimally verbal to those who show no impairments on standardized clinical assessments. Behavioral evidence indicates that this latter group demonstrates subtle syntactic deficits that are not necessarily apparent on clinical assessment. Language acquisition is a complex generalization task that requires the extension of learned form-to-meaning mappings to novel stimuli. Generalization itself, the process by which abstracted features of past experiences are extended to new instances, is an area of relative weakness in ASD. The current study aimed to determine whether linguistic generalization is an area of weakness in ASD, to compare the neural resources engaged for linguistic generalization in people with and without ASD, and to determine the degree to which linguistic generalization is a domain-general process. Methods: Seventeen young adults with ASD and 17 well-matched typically developing peers completed two experiments that tested the ability to abstract a principle and generalize it to new stimuli while undergoing functional magnetic resonance imaging. Experiment 1 tapped linguistic generalization, and Experiment 2 used a nonlinguistic visuospatial generalization task for comparison. Each experiment involved a manipulation of generalization distance, or the degree of difference between the exposure and test stimuli. Results: In the linguistic experiment, participants were more accurate and responded more rapidly on trials involving a small generalization distance compared to a large distance. ASD participants were marginally less accurate than TD participants, p=.06. Task performance in the ASD group only was driven by nonverbal IQ and deductive reasoning. Across groups, the linguistic generalization task engaged a robust network of task-correlated bilateral cortical and subcortical structures. Although neither main effects of group nor of generalization distance survived statistical correction for whole-brain analysis, trends for group differences in both directions were observed in frontal, temporal, and occipital regions. In the visuospatial experiment, there was no group difference in accuracy. Surprisingly, participants were more accurate on trials involving a larger generalization distance, though, in the ASD group, reaction times were longer for those trials. As with the linguistic task, the visuospatial task elicited broad activation across the cortex and in subcortical regions, but group differences did not survive statistical correction. Trends for group differences in both directions were extracted. Conclusion: The results provide novel insights into the overlap between generalization and language. They expose clinically relevant differences in generalization in a group with language vulnerability. Clinical implications include the consideration of specific supports for generalization in interventions targeted to high-functioning, highly-verbal adults with ASD. These findings provide a basis for understanding the neural circuitry supporting generalization, and they highlight the interplay of language and other cognitive faculties.
Themes: Disorders: Developmental, Syntax
Method: Functional Imaging