Neural Response to Biological Motion in Males and Females with ASD
Females are diagnosed with ASD less frequently than males (at a 1:4 ratio). For this reason, most published research either excludes females or is underpowered to analyze sex differences. Consequently, the behavioral and neural characteristics of ASD in females are poorly understood. Prior research has established that hemodynamic markers of biological motion perception are attenuated in individuals with ASD, and females with ASD show more attenuated electrophysiological markers of face processing, the N170, than males with ASD or typically developing controls. However, the early time course of biological motion perception in females with ASD remains unstudied.
A four-site network was created to recruit sufficient numbers of females with ASD to allow for comparisons across sex and diagnostic groups. This approach allows us to assess the temporal neural dynamics of biological motion processing in girls with ASD towards the end of elucidating the neural and behavioral phenotype of females with ASD.
Preliminary data from 13 TD (6 female) and 19 ASD (9 female) children between the ages of 8 and 17 observed biological motion (point light displays of walking humans) or non-biological motion (scrambled motion) while EEG was recorded at 500hz from a 128 channel Geodesic Sensor net. Mean amplitude of the N170 to biological and non-biological motion was measured at lateralized occipitotemporal recording sites.
Results from our preliminary sample identify differences between diagnostic status and sex on neural response to biological and non-biological motion. Overall there was a significant interaction between hemisphere, condition, and diagnoses [F= 4.65, p=.04]. These results show that differences between biological and non-biological motion were most apparent in the right hemisphere. Within the right hemisphere there was a significant interaction between condition and diagnosis [F=9.67, p=.004] such that TD individuals exhibited more negative N170s to biological versus non-biological motion. A marginal interaction between condition, diagnosis, and sex [F=3.49, p=.072] indicated that ASD females exhibited a less negative N170 to biological motion relative to non-biological motion, while ASD males displayed the opposite pattern. In contrast, all TD individuals exhibited more negative N170s to biological motion. Group differences were attributable to differences between TD and ASD females. Separate repeated measures ANOVAs by sex revealed significant condition by diagnoses interactions in females [F=10.04, p=.007] but not males [F=.96, p=.34].
These results suggest that perception of socially relevant stimuli may be more impaired in females than in males with ASD. This finding is consistent with reports that females with ASD exhibit more severe impairments in social and communicative function. Ongoing data collection and analyses (in 40 additional subjects) will address temporal dynamics of social brain function in females with ASD, and will include age in the analyses. Additional analyses in progress will assess brain response to additional EEG components and oscillatory activity and examine relationships among neural metrics and clinical characteristics.