Examining Phenotypic Differences in Gaze Avoidance Between Autism Spectrum Disorder and Fragile X Syndrome

Differential Effects of a Behavioral Treatment Probe on Social Gaze Behavior in Fragile X Syndrome and Non-Syndromic Autism Spectrum Disorder

The purpose of this study was to examine potential differences in social learning between individuals with fragile X syndrome (FXS), the leading known inherited cause of intellectual disability, and individuals with non-syndromic autism spectrum disorder (ASD). Thirty school-aged males with FXS and 26 age and symptom-matched males with non-syndromic ASD, were administered a behavioral treatment probe designed to improve levels of social gaze during interactions with others. The treatment probe was administered by a trained behavior therapist over two days in our laboratory and included reinforcement of social gaze in two alternating training conditions - looking while listening and looking while speaking. Prior to each session, children in each group were taught progressive muscle relaxation and breathing techniques to counteract potential increased hyperarousal. Measures included the rate of learning in each group during treatment, in addition to levels of social gaze and heart rate obtained during administration of a standardized social conversation task administered prior to and following the treatment probe. Results showed that learning rates obtained during administration of the treatment probe were significantly less steep and less variable for males with FXS compared to males with non-syndromic ASD. Significant improvements in social gaze were also observed for males with FXS during the social conversation task. There was no effect of the treatment probe on heart rate in either group. These data reveal important differences in social learning between the two groups and have implications for early interventions in the two conditions.

A failure to discriminate social from non-social touch at the circuit level may underlie social avoidance in autism

Social touch is critical for communication and to impart emotions and intentions. However, certain autistic individuals experience aversion to social touch, especially when it is unwanted. We used a novel social touch assay and Neuropixels probes to compare neural responses to social vs. non-social interactions in three relevant brain regions: vibrissal somatosensory cortex, tail of striatum, and basolateral amygdala. We find that wild type (WT) mice showed aversion to repeated presentations of an inanimate object but not of another mouse. Cortical neurons cared most about touch context (social vs. object) and showed a preference for social interactions, while striatal neurons changed their preference depending on whether mice could choose or not to interact. Amygdalar and striatal neurons were preferentially modulated by forced object touch, which was the most aversive. In contrast, the Fmr1 knockout (KO) model of autism found social and non-social interactions equally aversive and displayed more aversive facial expressions to social touch when it invaded their personal space. Importantly, when Fmr1 KO mice could choose to interact, neurons in all three regions did not discriminate social valence. Thus, a failure to differentially encode social from non-social stimuli at the circuit level may underlie social avoidance in autism.

Brief intensive social gaze training reorganizes functional brain connectivity in boys with fragile X syndrome

Boys with fragile X syndrome (FXS), the leading known genetic cause of autism spectrum disorder (ASD), demonstrate significant impairments in social gaze and associated weaknesses in communication, social interaction, and other areas of adaptive functioning. Little is known, however, concerning the impact of behavioral treatments for these behaviors on functional brain connectivity in this population. As part of a larger study, boys with FXS (mean age 13.23 ± 2.31 years) and comparison boys with ASD (mean age 12.15 ± 2.76 years) received resting-state functional magnetic resonance imaging scans prior to and following social gaze training administered by a trained behavior therapist in our laboratory. Network-agnostic connectome-based predictive modeling of pretreatment resting-state functional connectivity data revealed a set of positive (FXS > ASD) and negative (FXS < ASD) edges that differentiated the groups significantly and consistently across all folds of cross-validation. Following administration of the brief training, the FXS and ASD groups demonstrated reorganization of connectivity differences. The divergence in the spatial pattern of reorganization response, based on functional connectivity differences pretreatment, suggests a unique pattern of response to treatment in the FXS and ASD groups. These results provide further support for implementing targeted behavioral treatments to ameliorate syndrome-specific behavioral features in FXS.