Neurophysiological Findings From Magnetoencephalography in Autism Spectrum Disorder: a Comprehensive Review

Abstract

Autism spectrum disorder (ASD) is an etiologically and clinically heterogeneous group of neurodevelopmental disorders, diagnosed exclusively by the behavioral phenotype. The neural basis of altered social, communicative, somatosensory, and restricted and repetitive behaviors remains largely unknown. Magnetoencephalography (MEG) provides a vital method of inquiry to identify the neurophysiological mechanisms of ASD, better illuminate etiologically distinct subgroups, understand the developmental trajectories of aberrant connectivity and track outcome. MEG is a neuroimaging methodology that can localize sources of electrical activity within the brain with millisecond resolution by noninvasively measuring the magnetic fields arising from such activity. This review addresses the central MEG findings exploring auditory, visual and somatosensory processing, higher-order/executive functioning, and resting state in individuals with ASD over the past decade and a half. We offer a summary of emerging trends related to neurophysiological alterations, aberrant hemispheric specialization and connectivity, as well as limitations in the literature and recommendations for future MEG investigations.

Electrophysiological signatures of atypical intrinsic brain connectivity networks in autism

“…This pattern of resting-state functional connectivity changes in ASD is also supported by observations of atypical cortical oscillations from EEG/MEG data (Lajiness-O’ Neill et al, 2014; Wang et al, 2013). EEG/MEG signals, in a range of frequencies, are a putative hallmark of different local and large-scale network interactions (Siegel et al, 2012; Uhlhaas et al, 2010), and provide new insights into circuit mechanisms underlying atypical functional organization of brain networks in ASD (e.g., oscillatory frequency-band specific effects), which cannot be revealed by fMRI (Logothetis, 2008).…”

“…As frequency-specific network changes have been evidenced in EEG/MEG whole brain studies (Lajiness-O’ Neill et al, 2014; Wang et al, 2013), direct characterization of spatial patterns of ICNs from EEG/MEG data is thus better able to probe atypical functional connectivity in ASD with both precise spatial (i.e., electrophysiological ICNs) and spectral resolutions (i.e., cortical oscillations). Our results are consistent with a mixed profile of between network hypoconnectivity and local hyper-connectivity in ASD (Bos et al, 2014; Nomi and Uddin, 2015), but also suggest that these patterns vary across distinct functional networks and in the hierarchical structure of the whole brain network.…”

“…Disrupted functional connectivity has been reported in autism spectrum disorder (ASD) (Vissers et al, 2012; Wass, 2011) in functional magnetic resonance imaging (fMRI) (Muller et al, 2011; Rane et al, 2015), electroencephalography (EEG) (Boutros et al, 2015; Wang et al, 2013), and magnetoencephalography (MEG) data (Lajiness-O’ Neill et al, 2014). However, the nature of these disruptions, e.g., increased or decreased connectivity and their specificity in functional domains, remains elusive.…”

“…Studies of band-specific resting-state functional connectivity in ASD using EEG/MEG have shown reduced long-range connectivity in low-frequency bands (e.g., delta and theta) (Barttfeld et al, 2011; Coben et al, 2008; Ghanbari et al, 2015; Murias et al, 2007) and increased short-range connectivity in high-frequency bands (e.g., gamma) (Kitzbichler et al, 2015). While the range of connectivity patterns has been mostly claimed in terms of inter-channel distances on the scalp (Lajiness-O’ Neill et al, 2014; Wang et al, 2013), two recent MEG studies have further examined the resting-state whole brain network in ASD using cortical source imaging techniques (Kitzbichler et al, 2015; Ye et al, 2014). Graphic metrics calculated among anatomically defined cortical regions, i.e., 90 (Ye et al, 2014) and 148 (Kitzbichler et al, 2015), also demonstrated the mixed pattern of hyper- and hypo-connectivity at different frequency bands.…”

Fixel Based Analysis Reveals Atypical White Matter Micro- and Macrostructure in Adults With Autism Spectrum Disorder: An Investigation of the Role of Biological Sex

“…Therefore, the CC segments implicated in the present study project WM fibers to regions involved in the two core domains of autistic symptomatology; namely, social communication and repetitive behaviors/restricted interests (which, under DSM-5, now includes sensory sensitivities (American Psychiatric Association, 2013 ). Regarding the former, temporoparietal regions are strongly implicated in the cognitive processes involved in social understanding (Patriquin et al, 2016 ), while sensory difficulties experienced by affected individuals have been attributed to functional deficits within the somatosensory cortex (Lajiness-O’Neill et al, 2014 ). Indeed, Kana et al ( 2014 ) address the potential relationship between structural and functional neuropathophysiology in ASD by combining task-based fMRI and DTI to investigate the structural and functional neural correlates of theory of mind (ToM), a cognitive model of social understanding, in ASD.…”