An Electrocortical Measure Associated with Metarepresentation Mediates the Relationship between Autism Symptoms and Theory of Mind

Abstract

Impairments in theory of mind (ToM) - long considered common among individuals with autism spectrum disorder (ASD) - are in fact highly heterogeneous across this population. While such heterogeneity should be reflected in differential recruitment of neural mechanisms during ToM reasoning, no research has yet uncovered a mechanism that explains these individual differences. In this study, 78 (48 ASD) adolescents viewed ToM vignettes and made mental state inferences about characters' behavior while participant electrophysiology was concurrently recorded. Two candidate event-related potentials (ERPs) - the Late Positive Complex (LPC) and the Late Slow Wave (LSW) - were successfully elicited. LPC scores correlated positively with ToM accuracy and negatively with ASD symptom severity. Notably, the LPC partially mediated the relationship between ASD symptoms and ToM accuracy, suggesting this ERP component, thought to represent cognitive metarepresentation, may help explain differences in ToM performance in some individuals with ASD.

Keywords: Autism spectrum disorder; EEG; ERP; social cognition; theory of mind.

Figure 1.

Example of a typical ToM vignette. Images and audio narration are presented simultaneously. 1. Each vignette is comprised of four individual story panel images, followed by presentation of response options. 2. Three individual response options are presented sequentially, allowing target ERPs to be time-locked to the presentation of correct and incorrect response options. 3. All three response options are then displayed on screen simultaneously and participants are instructed to press the button on the button box corresponding to the colored circle displayed beneath the image of their response choice.

Figure 2.

Grand average event-related potentials (ERPs) (a) and topographical maps (b, c) for ASD, Non-ASD, and combined diagnostic groups during two post-stimulus time windows: (b) the late positive component (LPC; 300–600 ms) and (c) the late slow wave (LSW; 600–1200 ms). ERPs are recorded during the presentation of individual story panel pictures corresponding to correct and incorrect ToM response options, and pooled (averaged) across five parietal electrode sites (P7, P3, Pz, P4, P8) (data from individual channels are represented in Figure S3). Topographical maps represent the main effect of ToM response condition; mean amplitude difference is separated by diagnostic group and calculated by subtracting the ERP elicited by incorrect ToM conditions from the ERP elicited to correct ToM conditions.

Figure 3.

Unstandardized regression coefficients for the relationship between ASD symptom severity (ADOS-2 CS) and behavioral accuracy on the ToM EEG task (ToM Behavioral Accuracy) in adolescents with and without ASD is significantly mediated by the residualized difference score of the Late Positive Complex (LPC_resid) (b=−0.005, SE=0.004, 95% CI=−0.015, −0.0001). This mediation effect has a medium effect size according to Preacher and Kelley (2011): κ² = 0.120, SE 0.070, 95% CI 0.011, 0.279. Both the direct and indirect relationships between ASD symptom severity and ToM behavioral accuracy are illustrated. Standard errors are noted in parentheses, and 95% confidence intervals (CI) are displayed below in italics. *p< .05, **p< .01.