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Sex-Related Differences in Youth with ASD: Alpha EEG Power in Eyes-Open and Eyes-Closed Conditions from the ACE Gendaar Network
The EEG alpha frequency band (8-12 Hz) is thought to reflect levels of cortical excitability, with greater alpha power indicating lower cortical activity. Prior studies have demonstrated that individuals with ASD have decreased alpha power at rest (with eyes open) compared to control but comparable alpha power in eyes-closed (for review: Wang et al., 2013). The disparity in eyes-open vs eyes-closed alpha power is attributed to failure of individuals with ASD to increase cortical activity in preparation for visual input (e.g., Mathewson et al., 2012). Additionally, sex differences in resting EEG have been demonstrated in neurotypical participants, with females spend demonstrating lower power (greater attentional processes) compared to males (Tomescu et al, 2018). Little is known about sex-based difference in brain functioning in individuals with ASD, as most studies enroll males with ASD.
Objectives:
This study will evaluate resting-state EEG alpha power in youth with ASD, comparing alpha power during eyes-open and eyes-closed resting conditions. Analyses will focus on exploring sex differences within youth with and without ASD.
Methods:
EEG was collected as part of the ACE GENDAAR network. EEG data were collected while the participants passively watched screen-saver-like videos (eyes-open) and while sitting with eyes closed (eyes-closed). To be included in the analysis, youth had to provide artifact free data in both conditions. EEG data was available from 61 youth with ASD (males=35, females=26), 24 siblings of the youth with autism (males=12, females=12), and 94 neurotypical youth with no family history of autism (males=50, females=44). A fast fourier transformation (FFT) was performed on artifact-free EEG data to assess alpha power averaged across mid-posterior electrodes. Linear regressions were used to evaluate the effects of sex and diagnosis on alpha power.
Results:
Regression models with group, sex, and age as predictors of eyes-open frontal alpha power were significant for the eyes-open calm viewing alpha power at all regions (Fs>9.698, ps<.001, R2=.111-.137). Higher power (less activation) was found in the ASD group compared to NT (ps<.05) and for younger participants compared to the older (ps<.01). For eyes-closed frontal alpha power, the regression model was significant for eyes-closed at all regions (F≥2.62, ps≤.05, R2=.033-.39). Higher power was found in the ASD group compared to NT (ps<.05) and for the females compared to the males (ps<.05).
Conclusions:
EEG resting brain activity significantly differed between youth with ASD and youth with NT development. In the eyes-open condition, EEG power also differed for age; while for the eyes-closed condition, power differed by sex. These analyses extend previous findings to a sample of youth with ASD. Additional analyses will examine the relation between eyes-open and eyes-closed, include the interaction between these main effects, and the relation to phenotypic characteristics.