Correlations of Quantitative EEG with Language and Cognitive Functioning As Biomarkers of Autism Spectrum Disorders

Background: Quantitative electroencephalography (QEEG) allows for analysis of the strength of neural activity at different natural frequencies, and its use as a biomarker for various aspects of autism spectrum disorders (ASD) has shown particular promise.

Objectives: In order to determine QEEG’s potential as a biomarker of language and cognitive functioning in children with an ASD, we investigated EEG power in the theta (4-8 Hz), alpha (8-12 Hz), and gamma (35-45 Hz) frequency bands of preschool-aged children (ages 26-75 months) with an ASD and typically developing (TD) controls. Our objectives were to: (1) investigate if theta, alpha, and/or gamma power correlate with language and IQ in children with an ASD, and (2) determine if band power can be used as a biomarker of language and/or cognitive functioning for children or subgroups of children with an ASD. This is the first study to use such a heterogeneous population of children with an ASD, and as such is well suited to investigate subgroups within the disorder.

Methods: Two minutes of resting-state EEG data were recorded from 69 children with an ASD and 48 typical developing controls. Children were at rest while watching a video of bubbles. EEG recordings were acquired at 250 Hz using a 128-electrode Hydrocel Geodesic Sensor Net System (EGI Inc.). Offline processing of each child’s EEG included, band pass filtering, segmenting into one second epochs, and examining for artifact contaminated data. Using Matlab (Matlab Inc.), absolute and relative power were calculated for theta, alpha, and gamma bands in order to obtain a measurement of the power spectral density (PSD) for each frequency band. Depending on the age and developmental level of each child, a combination of the Mullen Scales of Early Learning (MSEL), Wechsler Preschool and Primary Scale of Intelligence (WPPSI-IV), the Differential Abilities Scale (DAS-II), Preschool Language Scale-4 (PLS-4), and Clinical Evaluation of Language Fundamentals (CELF) were administered to all children.

Results: Both the TD and ASD groups displayed significant differences in power correlations with language and IQ. Major group differences included: IQ correlated positively with frontal theta power for the TD group, but negatively for the ASD group; non-verbal IQ correlated positively with posterior alpha power, but only for the TD group; and both IQ and language measures correlated with regional gamma power, but correlations were positive for the TD group and negative with the ASD group. In fact, significant correlations for the TD group were predominantly in the positive direction, whereas correlations for the ASD group were in the negative direction.

Conclusions: Correlations of QEEG band power with language and cognitive functioning have the potential to aid in distinguishing children with an ASD from TD children.