Sex Differences in Adaptive and Social Behavior and Neural Responses to Biological Motion before and after Pivotal Response Treatment in Autism

Background:  Research on the clinical presentation of girls with ASD is mixed. Some evidence indicates that girls are more severely affected than boys; however, some girls with ASD may be missed by current diagnostic criteria (Kirkovski, M., Enticott, P.G., Fitzgerald, P.B., 2013; Howe, Y.J., et al, 2015). It is also unclear whether sex differences exist in treatment response.

Objectives:  In a sample of young children with ASD, we compared social communication and adaptive skills as well as neural activation in key regions of social perception before and after a 16-week waitlist controlled trial of Pivotal Response Treatment (PRT).

Methods:  Twenty-eight children, eleven girls, (mean IQ 96.32; SD 20.39; range 50-128) completed the 16-week trial of PRT. Twenty-one children, six girls, completed the waitlist condition (WLC) (mean IQ 97.00; SD 23.49; range 50-128). Furthermore, a subset of the PRT sample (13 boys, 7 girls) completed an fMRI before and after treatment. They viewed neuroimaging stimuli depicting point light displays of coherent biological or scrambled motion in a 3T scanner. Neuroimaging results were thresholded at Z>2.33 (voxel) and p<.05 (cluster). PRT is a naturalistic behavioral treatment focusing on improving children’s social communication skills. PRT condition included 7 hours per week of individual work with the child and parent training. Clinical outcomes were assessed using the SRS-2, a parent report measure of social communication, and the Vineland Adaptive Behavior Scales-II, a semi-structured interview on adaptive functioning.

Results: At baseline, girls had significantly greater impairments in all domains of the Vineland-II (girls Communication mean 80.75, boys 91.588, p<.05; girls Daily Living Skills mean 74.833, boys 88.353, p<.05; girls Socialization mean 75.333, boys 82.47, p<.05; girls Adaptive Behavior Composite mean 76.167, boys 85.188, p<.05). Following treatment, girls’ improvement on the ABC was significant (p<.05), whereas boys’ improvement was not. After treatment, girls and boys exhibited no significant differences in adaptive functioning. At baseline, girls also had more pronounced social communication deficits than boys as assessed by the SRS-2. Girls’ rate of improvement exceeded boys’, although the magnitude of the differences was not significant (p>.05). Neither boys nor girls exhibited significant change in adaptive functioning or social communication following the WLC. Neuroimaging results were consistent with behavioral results: at pretreatment baseline, girls exhibited significantly less response to biological vs. scrambled motion than boys in the right inferior frontal gyrus (IFG) and right precentral gyrus (PG), key regions of social information processing. Following treatment, girls exhibited a greater gain in activation in the left fusiform gyrus (FFG), another key region involved in social perception. No regions showed a greater improvement in boys than girls.

Conclusions:  Compared to boys, girls were more impaired at baseline and made more progress in adaptive functioning. Girls’ social communication gains trended toward being significantly greater than boys’. Neuroimaging results were consistent with behavioral results. These findings are promising in that they suggest that girls, even if more impaired at baseline, respond favorably to treatment at the behavioral and neural level, possibly even more so than boys.