Electrophysiological Markers of Social Perception in Infants At Risk for Autism

Background:

Perceptual sensitivity to the motion of other people is a fundamental building block of social interaction, present from the first days of life in humans. Infants as young as two days old prefer to view point-light displays depicting human movement (e.g., walking) compared to scrambled motion. Perception of biological motion is linked to specific electrophysiological indexes. It elicits reduction in power in the mu frequency band measured at central electrode sites, a pattern associated with mirror neuron system activity in adults. Biological motion perception also evokes increased activity in the gamma band at parieto-temporal electrode sites; this activation pattern has been associated with top down integrative processes in both children and adults. Electrophysiological markers of biological motion perception reveal neural differentiation of upright and inverted point light walkers in infants as young as 8 months. Though behavioral studies show that toddlers with ASD fail to exhibit a preference for biological motion, little is known about the neural underpinnings of biological motion processing in children with ASD. In the current study, we apply established electrophysiological methods to elucidate early brain development in autism.

Objectives:  

The present study investigates the development of neural sensitivity to biological motion during the first 18 months of life in infants at high- and low-risk for ASD and its relationship to behavioral phenotypes. 

Methods:

Participants include two groups of infants assessed longitudinally at three-month time points between 3 and 18 months of age. EEG was recorded with a128-channel Hydrocel Geodesic Sensor net while infants viewed point-light displays depicting a person walking (biological motion) and a spatio-temporally scrambled dot array (non-biological motion). EEG data was segmented to the onset of the video displays, and time-frequency domain analyses extracted event-related oscillatory activity in mu (6-9 Hz) and gamma (30-50 Hz) bands across the two experimental conditions. Infants were administered the Mullen Scales of Early Learning at each visit and a comprehensive battery of social and communicative assessments.

Results:  

Preliminary analyses in infants at 12 months indicate a distinct response pattern to biological motion in low-risk infants: enhanced mu suppression at ~200ms and greater gamma power at ~170ms. This response pattern is attenuated in the group of high-risk infants. Correlational analyses in progress will examine interrelationships between these distinct patterns of oscillatory activity (i.e., mu and gamma) and social and communicative developmental functions.

Conclusions:  

Results demonstrate electrophysiological markers of biological motion perception in infants.  These patterns are attenuated in infants at risk for autism, providing promise for a non-invasive biologically-based method of measuring development of brain systems implicated in autism before onset of the disorder.