Reduced neural sensitivity to rapid individual face discrimination in autism spectrum disorder

Sofie Vettori, Milena Dzhelyova, Stephanie Van der Donck, Corentin Jacques, Jean Steyaert, Bruno Rossion, Bart Boets, Sofie Vettori, Milena Dzhelyova, Stephanie Van der Donck, Corentin Jacques, Jean Steyaert, Bruno Rossion, Bart Boets

Abstract

Background: Individuals with autism spectrum disorder (ASD) are characterized by impairments in social communication and interaction. Although difficulties at processing social signals from the face in ASD have been observed and emphasized for many years, there is a lot of inconsistency across both behavioral and neural studies.

Methods: We recorded scalp electroencephalography (EEG) in 23 8-to-12 year old boys with ASD and 23 matched typically developing boys using a fast periodic visual stimulation (FPVS) paradigm, providing objective (i.e., frequency-tagged), fast (i.e., few minutes) and highly sensitive measures of rapid face categorization, without requiring any explicit face processing task. We tested both the sensitivity to rapidly (i.e., at a glance) categorize faces among other objects and to individuate unfamiliar faces.

Outcomes: While general neural synchronization to the visual stimulation and neural responses indexing generic face categorization were undistinguishable between children with ASD and typically developing controls, neural responses indexing individual face discrimination over the occipito-temporal cortex were substantially reduced in the individuals with ASD. This difference vanished when faces were presented upside-down, due to the lack of significant face inversion effect in ASD.

Interpretation: These data provide original evidence for a selective high-level impairment in individual face discrimination in ASD in an implicit task. The objective and rapid assessment of this function opens new perspectives for ASD diagnosis in clinical settings.

Keywords: Autism; EEG; Face processing.

Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Figures

Fig. 1
Fig. 1
Fast periodic visual stimulation (FPVS) paradigms used in 2 separate experiments to test generic face categorization and individual face discrimination.
Fig. 2
Fig. 2
Spectral representation and scalp distribution of EEG signal during FPVS.
  1. A.

    Similar generic face categorization response in ASD and TD. SNR spectrum over the averaged electrodes of left and right occipito-temporal (OT) ROI (indicated with open circles on the topographical maps). ASD (green) and TD boys (blue) show similar face-selective responses, reflected by equal amplitudes at the face presentation frequency (1.2 Hz) and harmonics (2.4 Hz, 3.6 Hz, …). The response is quantified by summing the baseline-corrected amplitudes over all significant harmonics and is visualized in scalp topographies and bar graphs. Scalp topographies show that the distribution of the face-selective response is also qualitatively similar in both groups. Bar graphs (mean ± SEM) show that the amplitudes of responses in LOT and ROT are similar for both groups.

  2. B.

    Reduced individual face discrimination response to upright faces in ASD. SNR spectra, scalp topographies and bar graphs of left and right OT are shown for the conditions with upright and inverted faces. *: p < 0.05; **: p < 0.01.

Fig. 3
Fig. 3
Violin plot of the ten-dimensional data of the relevant harmonics of the individual face discrimination response, projected along the LDA projection vector. The LDA was fitted to the full dataset and illustrates the separability of the groups. The horizontal line represents the decision boundary of the LDA classifier.

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