Heightened functional excitation-inhibition ratio as a compensatory mechanism in autism spectrum disorder (ASD): an EEG study

Abstract

Abstract Background: Abnormal global brain signaling, which is associated with impaired neural connectivity, is evident in people with autism spectrum disorder (ASD), yet its association with impeded cognitive processes underlying social information processing and ASD symptomatology remained elusive. Methods: This study aimed to investigate the local and global brain signaling in ASD indicated by functional excitation-inhibition (fE/I) ratio and explored psychophysiological relationships between regional/global fE/I ratios and interference control, set-shifting as well as ASD symptomatology. Thirty-one ASD and 30 age-, intelligence quotient (IQ), sex- and handedness-matched TD individuals (aged 14-21) participated in this study. CANTAB Multitasking Task was used to assess the cognitive processes (i.e. interference control, set-shifting, set-maintenance) supporting daily information processing. Resting-state electroencephalography (EEG) was used for estimating regional and global fE/I ratio. Results: When compared to TD individuals, although individuals with ASD showed comparable error rates (ps > .084), they were shown to have slower processing speed specifically in CANTAB Multitasking Task trials tapping interference control and set-maintenance abilities (Bonferroni-corrected ps < .006). Electrophysiological data revealed that, heightened fE/I ratios were observed at the whole-brain level and the right hemisphere in ASD (Bonferroni-corrected ps < .005). Within the ASD group, higher global and right hemispheric fE/I ratios were significantly correlated with faster reaction time in the CANTAB Multitasking Task incongruent trials, of which faster incongruent trial reaction time was significantly associated with less severe ASD symptom in the social interaction and restricted, repetitive behavior domains (FDR-corrected ps < .05). Limitations: The generalizability of results is limited by the inclusion of only males with ASD with normal range of IQ. The relationship between fE/I and cognitive-behavioral deficits in females with ASD, as well as those with lower IQ is yet to be explored by future studies. Conclusion: Altered local and global brain signaling is evident in ASD. It appears that heightened fE/I in ASD is a compensatory mechanism that supports a more efficient filtering of distractors during attention task and a less severe ASD symptom manifestation.