Brain Connectivity during a High-Level Visual Perceptual Task in Young ASD Children: A MEG Investigation

Background: Enhanced local connectivity in autism has been mostly demonstrated through resting-state fMRI studies (Keown et al, 2013, Supekar et al, 2013). However, task-related connectivity is fairly low in these regions (Liu et al, 2011; De Ramus et al, 2014). Coherence of electrophysiological signal between pairs of regions is another method to assess task-related connectivity (Kikuchi et al 2013, Kenet 2014). Among the frequency bands that can be investigated by MEG, gamma-frequency oscillations between neural networks are believed to represent ongoing cognitive processes during the perception of visual patterns.

Objectives: We sought to investigate local, task-related connectivity associated with the performance of a mental rotation task in young ASD children of typical intelligence.

Methods: MEG data were acquired during a mental rotation task (modified version of The Purdue Spatial Visualization Tests: Visualization of Rotations) with a custom child-sized MEG system, which facilitates the measurement of brain activities in young children. Recordings were obtained with a 151-channel SQUID (Superconducting Quantum Interference Device), whole-head coaxial gradiometer MEG system for children (PQ 1151R; Yokogawa/KIT, Kanazawa, Japan). Coherence values were examined in the following two bands: gamma-1 (31.0 – 58.0 Hz) and gamma- 2 (62.0 – 80.0 Hz). Eighteen ASD children (age: 83.9 months [59 - 111], mean IQ 105 [77 - 145]) were included in this study.They were diagnosed with childhood autism (n = 13), atypical autism (n = 4) or Asperger's syndrome (n = 1) according tothe Diagnostic Interview for Social and Communication (DISCO) criteria.Parents consented to their child’s participation in the study and had full knowledge of the nature of the research. Written informed consent was obtained prior to enrolment in the study. The Ethics Committee of Kanazawa University Hospital approved the methods and procedures, all of which were in accordance with the Declaration of Helsinki.

Results: Autistic children performed the mental rotation task faster than the control group (see behavioral results in Kikuchi et al, joint communication). There was a negative correlation (Pearson) between task performance and coherence in the gamma-1 band in several intra-hemispheric pairs of regions (the centro-occipital and front-parietal networks in the right hemisphere, and the temporo-parietal and temporo-central networks in the left hemisphere; P < 0.0025) and in the gamma-2 band in one intra-hemispheric region (the centro-frontal network in the left hemisphere; P < 0.0025).

Conclusions: In contrast with the findings of most fMRI resting states studies, our results reveal low connectivity between associative visual regions and the parietal lobe during the performance of high level visual tasks in autistic children. This atypical low connectivity may contribute to the strong performance of these children in visual tasks. The results of this independent method confirm those obtained by task-related fMRI showing low connectivity between the inferior temporal area and the parietal and occipital areas during the detection of locations in high-level visual tasks. How and why these neurophysiological correlates favor exceptional behavioral performance in such tasks remains to be investigated.