Investigating EEG Delta Band Differences in Preschool Children with Autism during Awake and Sleep Stages

BACKGROUND: Electroencephalography (EEG) studies in Autism Spectrum Disorder (ASD) have investigated spectral power, coherence of EEG rhythms and asymmetry of the bands across various brain regions. There is inadequate evidence for ascertaining hemispherical dominance/asymmetry of bands in sleep states. In this study, we aim to compute spatial delta asymmetries across cerebral hemispheres using EEG in preschool children with ASD in comparison to non-ASD age matched clinical controls in awake and sleep stages. METHODS: Preschool children (2 to 6 years of age) underwent natural EEG recording up to 180 mins with 64 Channel EGI-GES400 system. ASD group had 28 children (24M, 4F). Controls who were diagnosed with ADHD, Specific Speech Delay, and Global Developmental Delay had 10 children (6M, 4F). None were on medication. Awake state, sleep stage 1 (N1), 2 (N2) and (N3) were included. An artefact-free continuous segment of 60s in all stages was selected manually. Power Spectral Density was computed for each epoch of 10s duration with 50% overlap using Welch’s periodogram. Delta [0.5-4Hz] power& asymmetry indices were computed for 36 scalp locations spanning 10 regions in both hemispheres (frontal, central, parietal, temporal and occipital regions). RESULTS: N1 had right hemispherical dominance in only parietal & occipital. N2 was left central dominant for ASD. N3 had total right dominance across all areas with ASD > non-ASD throughout. CONCLUSIONS: We demonstrate EEG Delta band power differences in multiple cerebral regions indicating divergence in activities measure by spectral density which could be related to autistic trait differences and tendencies.