Investigating Mirror System (MS) Activity in Adults with ASD When Inferring Others' Intentions Using Both TMS and EEG

Abstract

ASD is associated with mentalizing deficits that may correspond with atypical mirror system (MS) activation. We investigated MS activity in adults with and without ASD when inferring others' intentions using TMS-induced motor evoked potentials (MEPs) and mu suppression measured by EEG. Autistic traits were measured for all participants. Our EEG data show, high levels of autistic traits predicted reduced right mu (8-10 Hz) suppression when mentalizing. Higher left mu (8-10 Hz) suppression was associated with superior mentalizing performances. Eye-tracking and TMS data showed no differences associated with autistic traits. Our data suggest ASD is associated with reduced right MS activity when mentalizing, TMS-induced MEPs and mu suppression measure different aspects of MS functioning and the MS is directly involved in inferring intentions.

Keywords: Autism spectrum disorder (ASD); Electroencephalography (EEG); Intentions; Mentalizing; Mirror system (MS); Transcranial magnetic stimulation (TMS).

Fig. 1

Screenshots depicting the final frame of the video stimuli for one actor. The videos depict an actor: a Accidently dropping a poker chip (clumsy grasp). b Deliberately dropping a poker chip (spiteful grasp). c Passing a poker chip through the higher slot in the board (successful grasp). d Accidentally not passing a poker chip through the bottom slot (clumsy push). e Deliberately not passing a poker chip through the bottom slot (spiteful push). f Passing a poker chip through the bottom slot (successful push)

Fig. 2

The dynamic regions of interest (ROIs) used in the eye-tracking data analysis for one of the action videos are shown overlaid onto screenshots from a the start and b the end of that particular video. Three dynamic ROIs corresponding to (1) The poker chip, (2) The actor’s head and (3) The actor’s hand, were created for each of the 120 videos individually

Fig. 3

The relationship between the level of autistic traits that participants displayed and the level of mu suppression in the 8–10 Hz frequency range at F4. Levels of autistic traits significantly predicted the degree of mu suppression at F4; participants that exhibited higher levels of autistic traits showed lower levels of mu suppression (8–10 Hz) at F4 [F(1,38) = 0.47, p = 0.04, R² = 0.11]. The curved lines represent 95% confidence intervals

Fig. 4

The relationship between performance on the mentalizing task and the level of mu suppression in the 8–10 Hz frequency band at F3. Mentalizing performance significantly predicted the degree of mu suppression at F3; participants with superior mentalizing performances also showed greater levels of mu suppression at F3 in the 8–10 Hz frequency band [F(1,38) = 5.64, p = 0.02, R² = 0.13]. The curved lines represent 95% confidence intervals