Autism spectrum disorder (ASD) is more prevalent in males than females. Previous research indicates females camouflage ASD symptoms more than males, potentially contributing to the difference in prevalence. This study investigated sex/gender differences in behavioral phenotypes in 17 males and 11 females with ASD, as well camouflaging in ASD, in an attempt to partially replicate findings from Lai et al. (Autism 21(6):690–702, 2017). Overall ASD symptoms were measured by the autism spectrum quotient (AQ). Mean AQ in females with ASD was higher than males with ASD, with the difference approaching statistical significance. Camouflaging was found to be more common in females with ASD, and not associated to social phobia. Furthermore, camouflaging correlated negatively with emotional expressivity in females, but not males, with ASD. These findings strengthen previous findings regarding camouflaging being more common in females and add to the literature on how camouflaging may be different in females versus males.

The gamma aminobutyric acid (GABA) neurotransmission system has been implicated in autism spectrum disorder (ASD). Molecular neuroimaging studies incorporating simultaneous acquisitions of GABA concentrations and GABA A receptor densities can identify objective molecular markers in ASD. We measured both total GABA A receptor densities by using [ 18 F]flumazenil positron emission tomography ([ 18 F]FMZ-PET) and GABA concentrations by using proton magnetic resonance spectroscopy ( 1 H-MRS) in 28 adults with ASD and in 29 age-matched typically developing (TD) individuals. Focusing on the bilateral thalami and the left dorsolateral prefrontal cortex (DLPFC) as our regions of interest, we found no differences in GABA A receptor densities between ASD and TD groups. However, 1 H-MRS measurements revealed significantly higher GABA/Water (GABA normalized by water signal) in the left DLPFC of individuals with ASD than that of TD controls. Furthermore, a significant gender effect was observed in the thalami, with higher GABA/Water in males than in females. Hypothesizing that thalamic GABA correlates with ASD symptom severity in gender-specific ways, we stratified by diagnosis and investigated the interaction between gender and thalamic GABA/Water in predicting Autism Quotient (AQ) and Ritvo Autism Asperger’s Diagnostic Scale – Revised (RAADS-R) total scores. We found that gender is a significant effect modifier of thalamic GABA/Water’s relationship with AQ and RAADS-R scores for individuals with ASD, but not for TD controls. When we separated the ASD participants by gender, a negative correlation between thalamic GABA/Water and AQ was observed in male ASD participants. Remarkably, in female ASD participants, a positive correlation between thalamic GABA/Water and AQ was found.

Alterations in sensorimotor functions are common in individuals with autism spectrum disorder (ASD). Such aberrations suggest the involvement of the thalamus due to its key role in modulating sensorimotor signaling in the cortex. Although previous research has linked atypical thalamocortical connectivity with ASD, investigations of this association in high-functioning adults with autism spectrum disorder (HFASD) are lacking. Here, for the first time, we investigated the resting-state functional connectivity of the thalamus, medial prefrontal, posterior cingulate, and left dorsolateral prefrontal cortices and its association with symptom severity in two matched cohorts of HFASD. The principal cohort consisted of 23 HFASD (mean[SD] 27.1[8.9] years, 39.1% female) and 20 age- and sex-matched typically developing controls (25.1[7.2] years, 30.0% female). The secondary cohort was a subset of the ABIDE database consisting of 58 HFASD (25.4[7.8] years, 37.9% female) and 51 typically developing controls (24.4[6.7] years, 39.2% female). Using seed-based connectivity analysis, between-group differences were revealed as hyperconnectivity in HFASD in the principal cohort between the right thalamus and bilateral precentral/postcentral gyri and between the right thalamus and the right superior parietal lobule. The former was associated with autism-spectrum quotient in a sex-specific manner, and was further validated in the secondary ABIDE cohort. Altogether, we present converging evidence for thalamocortical hyperconnectivity in HFASD that is associated with symptom severity. Our results fill an important knowledge gap regarding atypical thalamocortical connectivity in HFASD, previously only reported in younger cohorts.

No abstract

No abstract