Resting-State Alpha in Autism Spectrum Disorder and Alpha Associations with Thalamic Volume

Abstract

Alpha circuits (8–12 Hz), necessary for basic and complex brain processes, are abnormal in autism spectrum disorder (ASD). The present study obtained estimates of resting-state (RS) alpha activity in children with ASD and examined associations between alpha activity, age, and clinical symptoms. Given that the thalamus modulates cortical RS alpha rhythms, associations between thalamic structure and alpha activity were examined. RS magnetoencephalography was obtained from 47 typically-developing children (TDC) and 41 children with ASD. RS alpha activity was measured using distributed source localization. Left and right thalamic volume measurements were also obtained. In both groups, the strongest alpha activity was observed in Calcarine Sulcus regions. In Calcarine regions, only TDC showed the expected association between age and alpha peak frequency. ASD had more alpha activity than TDC in regions bordering the Central Sulcus as well as parietal association cortices. In ASD, whereas greater left Central Sulcus relative alpha activity was associated with higher Social Responsiveness Scale (SRS) scores, greater Calcarine region relative alpha activity was associated with lower SRS scores. Although thalamic volume group differences were not observed, relationships between thalamic volume and Calcarine alpha power were unique to TDC. The present study also identified a failure to shift peak alpha frequency as a function of age in primary alpha-generating areas in children with ASD. Findings suggested that increased RS alpha activity in primary motor and somatosensory as well as parietal multimodal areas—with increased alpha thought to reflect greater inhibition—might impair the ability to identify or interpret social cues. Finally, to our knowledge, this is the first study to report associations between thalamic volume and alpha power, an association observed only in TDC. The lack of thalamic and alpha associations in ASD suggests thalamic contributions to RS alpha abnormalities in ASD.

Neuroimaging with magnetoencephalography: A dynamic view of brain pathophysiology

“…29-32 For example, Edgar and colleagues investigated a large group of ASD and typically-developing children and found that alpha activity was stronger in the sensorimotor and parietal association cortices of the ASD group, and that alpha power in these regions correlated with scores on a social responsiveness scale. 30 Group differences were not observed in other areas, although the well-known correlation between peak occipital alpha frequency and age was notably missing in children with ASD. 30 Connectivity studies using MEG have found hyper-connectivity among frontal, temporal, and subcortical regions in the beta and gamma frequencies of children with ASD, including an orbitofrontal, subcortical, and temporal network implicated in social cognition.…”

“…30 Group differences were not observed in other areas, although the well-known correlation between peak occipital alpha frequency and age was notably missing in children with ASD. 30 Connectivity studies using MEG have found hyper-connectivity among frontal, temporal, and subcortical regions in the beta and gamma frequencies of children with ASD, including an orbitofrontal, subcortical, and temporal network implicated in social cognition. 31 The same study also found that parietal and occipital regions were hypo-connected to most brain regions in the theta and alpha ranges in the ASD compared to typically-developing group, and that children with ASD had altered network topology at both global and local levels.…”

Measuring neural excitation and inhibition in autism: Different approaches, different findings and different interpretations

“…Evoked activity is both phase-locked and time-locked to the onset of a stimulus; induced activity often occurs later than evoked activity, and whilst it is time-locked it is not phase-locked to the stimulus. While several studies have found evoked gamma band power to be reduced in ASD (Edgar et al, 2015;Baruth et al, 2010;Rojas, Maharajh What do changes in evoked and / or induced gamma band power suggest about E/I balance in ASD? There is little existing data that allows us to confidently link evoked gamma power to E/I balance, although one study suggests that evoked gamma power may be associated with glutamate levels, as Lally et al (2014) have reported a positive correlation between dynamic glutamate levels (measured using MRS) and evoked gamma band power (measured using EEG recorded from parietal and occipital electrodes; Lally et al, 2014).…”

Dysfunction of sensory oscillations in Autism Spectrum Disorder

“…Recent multimodal approaches combining fMRI and MEG have circumvented these challenges by leveraging the relative strengths of each technique to determine correspondence of thalamic characteristics and neural activity in ASD. One of these investigations found that thalamic volume and resting state α power are positively correlated in TD individuals, but that this relationship is does not exist in those with ASD (Edgar et al, 2015b) (Fig. 7).…”