30015
Endogenous Bold Signal Complexity of Ventromedial Prefrontal Cortex Is Different in Autistic Men Versus Women and Differentially Associated with Compensatory Behavioral Camouflaging

Poster Presentation
Friday, May 3, 2019: 11:30 AM-1:30 PM
Room: 710 (Palais des congres de Montreal)
S. Trakoshis1, W. You2, S. Baron-Cohen3, B. Chakrabarti4, A. N. Ruigrok5, E. Bullmore5, J. Suckling6, M. C. Lai7 and M. V. Lombardo5, (1)Department of Psychology, University of Cyprus, Nicosia, Cyprus, (2)Diagnostic imaging and radiology, Children's National Medical Center, Washington, D.C, WA, (3)Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom, (4)Centre for Autism, School of Psychology & Clinical Language Sciences, University of Reading, Reading, United Kingdom, (5)University of Cambridge, Cambridge, United Kingdom, (6)University of Cambridge, Cambridge, United Kingdom of Great Britain and Northern Ireland, (7)The Hospital for Sick Children, Toronto, ON, Canada
Background: Longstanding theories suggest that there may be an imbalance of excitation versus inhibition (E/I) in the autistic brain. E/I imbalance can result in increased neural noise with long-range dependence and this may be represented in the 1/f signal of non-invasive in-vivo measurements of brain function such as resting state fMRI (rsfMRI). The 1/f signal has been characterised with the Hurst exponent (H), indicating the temporally persistent behaviour (long memory) and stationarity of the signal when 0.5<H<1. However, rsfMRI BOLD signal exhibits non-stationary behaviour that also needs to be quantified. Thus we have utilised a novel approach for estimating H based on the fractionally integrated process (FIP) model to allow H>1, as a non-stationarity index. Using H as a metric of endogenous BOLD signal complexity, we examined how H may differ between males versus females with autism, by expanding on previous work on adult males (Lai et al., 2010). Here, we assess if H exhibits sex-by-diagnosis interaction effects when examined in a 2x2 design.

Objectives: To assess sex-by-diagnosis interactions in H and assess any sex-differential associations with clinical measures of behavioural camouflaging.

Methods: Age-matched male and female adults with ASD (males n=23; females n=25) and a typically developing (TD) group (males n=29; females n=33) were scanned with rsfMRI (3T, TR=1302 ms, 620 volumes) while awake with eyes closed. Data were preprocessed using a standard pipeline in AFNI, along with motion regression, CSF regression and wavelet despiking. Mean time-series from 180 parcels from the HCP parcellation (Glasser et al., 2016) were used to estimate H based on the FIP model. For each region, a linear model was constructed to examine main effects of sex and diagnosis along with the sex-by-diagnosis interaction, after covarying for mean framewise displacement and full-scale IQ. Multiple comparison correction was implemented with FDR q<0.05. A behavioural camouflaging index was computed identical to past work (Lai et al., 2017) and was utilised in correlation analyses with H, stratified by sex within autistic individuals.

Results: A region in ventromedial prefrontal cortex (vMPFC) showed evidence of a sex-by-diagnosis interaction (F=15.134, p=1.76e-4, partial η2=0.12) with a TD>Autism effect in males (d=1.30) but no strong effect in females (d=-0.27). Increasing vMPFC H was significantly associated with increasing behavioural camouflaging in females (r=0.60, p=0.0015), whereas no association was present in males (r=-0.10, p=0.63). The strength of these vMPFC H-camouflaging correlations was different between males versus females with autism (z=2.58, p=0.0098).

Conclusions: These results suggest that an important node of the ‘social brain’, vMPFC, shows lower H in men but not women with autism, compared to same-sex TD controls. Lower H could indicate enhanced neural noise and may impact several key functions of vMPFC involved in social and self-referential cognition, particularly in males with autism. This marker also explains variance in clinically relevant phenomena such as camouflaging, in a sex-differential manner, suggesting that the less neural noise present in vMPFC of females with autism may be related to enhanced ability to camouflage impairments in the social-communicative domain.

See more of: Neuroimaging
See more of: Neuroimaging