Resting-State Gamma Power and Early Language Function in Infants At Risk for Autism

Background: Oscillatory activity in the gamma frequency range (30-50 Hz) has been linked with various higher cognitive functions (e.g., attention, perception, language, etc.) and is thought to play a critical role in coordinating neural activity across cortical and subcortical networks.  There is growing support for the hypothesis that ASD may reflect aberrant functional connectivity and therefore gamma activity may serve as an important marker of this phenomenon.  A recent study looked at the development of oscillatory activity across early childhood and found that differences in frontal resting gamma power were highly correlated with concurrent language and cognitive skills at ages 16, 24, and 36 months (Benasich, 2008).  Another research group investigated gamma power in high-risk infants and showed that frontal gamma power was reduced in this group compared to low-risk controls (Bosl, 2011).  No prior studies have investigated the relationship between gamma and language function in infants at risk for autism.

Objectives: Here, we used resting-state EEG to examine high-frequency cortical activity in infants at high-risk for developing ASD and low-risk, age matched controls.  The aim was (a) to examine differences between groups in frontal gamma activity and (b) to study the link between frontal gamma activity and early language function.

Methods: Resting-state EEG was obtained for two minutes while infants were sitting quietly and watching bubbles produced by a bubble machine. EEG data were bandpass filtered from 1 to 50 Hz then divided into 1-second segments. Segments containing artifacts arising from eye-blinks, eye-saccades, and muscle movements were removed from subsequent analysis. Only subjects with a minimum of 30 seconds of artifact-free data were analyzed. The data were then transformed into the frequency domain using a Fast Fourier Transform. Relative frontal gamma power was calculated for each subject.  High-risk infants were compared to low-risk infants.  In addition, receptive language and expressive language domains on the Mullen Scales of Early Learning (MSEL) were correlated with relative gamma power within each group.

Results: Six high-risk 6 month-old infants and nine low-risk 6 month-old infants provided a minimum of 30 seconds of resting-state EEG data.  The data show significant differences between high-risk and low-risk infants in frontal gamma power, such that the high-risk infants had significantly decreased relative frontal gamma power (p=.025).  Furthermore, preliminary data analysis suggests a correlation between frontal gamma power and language ability, such that infants with increased gamma also have higher expressive language scores (p=.018).

Conclusions: Our preliminary data suggest that high-risk infants and low-risk control infants differ in high frequency oscillatory activity.  In addition, our data show that frontal gamma activity may be linked with language function in infancy.  Data collected from these infants at later time points can provide more insight into the development of gamma oscillations and its potential implications for ASD diagnosis and language acquisition.