Postural sway in infants at low and high risk for autism spectrum disorder

ABSTRACT Harris, Rachel C. M. S., Purdue University, December 2014. Postural Control in Infants at Low and High Risk for Autism Spectrum Disorder. Major Professor: Laura J. Claxton. Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder more commonly known for deficits in social and communication skills. More recently, aspects of motor development have been shown to be delayed in children with ASD, including deficits in their postural control abilities. Children with ASD have difficulty integrating information from their sensory systems to help control their balance. Infants at risk for ASD and infants who are later diagnosed with ASD have delays in acquiring their postural motor milestones. Whereas postural control differences have been documented in children with ASD as young as 5 years of age; it remains unknown whether infants at low and high risk will exhibit differing postural control abilities. The current study focused on examining postural control abilities in infants at low and high risk by measuring postural sway using center of pressure trajectory. We investigated sitting postural control in 12 9-month-olds (8 low risk, 4 high risk) and 19 12-month-old infants (14 low risk, 5 high risk) during two different somatosensory conditions: sitting on a solid surface and sitting on a foam surface. Four measures of postural sway were calculated for each age group: sway range in the anterior-posterior (AP) and medial-lateral (ML) directions, sway variance (AP and ML), sway velocity, and sway area. Overall, regardless of risk, both age groups had more center of pressure movement while sitting on a compliant foam surface. Nine-month-old infants had significantly larger sway variance in the AP direction. In addition, 9-month-old infants had a marginally significantly larger ML sway variance and sway area when sitting on the foam surface as compared to the solid surface. Similarly, regardless of risk, 12-month-old infants swayed significantly faster when sitting on the foam surface and had marginally significant larger range of sway (AP and ML), larger ML variance, and a greater area of sway while sitting on the foam surface. Interestingly, there was only a main effect of risk for the 9-month-old infants, not for the 12-month-old infants. Regardless of surface, 9- month-old infants at high risk had a significantly larger AP sway variance and a marginally significant larger AP sway range as compared to the infants at low risk. For the area of sway measure, there was a marginally significant interaction, such that while sitting on the solid surface, infants at high risk exhibited a greater area of sway than the low risk infants. However, there was no difference in the area of sway between the two risk groups while sitting on the foam surface. The findings contribute to our understanding of the development of the postural control system of infants at high risk