Deoni, S. C, Zinkstok, J. R, Daly, E. M, Ecker, C., Willia, S. C, Murphy, D., Bailey, A. J, Baron-Cohen, S., Bolton, P. F, Bullmore, E. T, Carrington, S., Chakrabarti, B., Daly, E. M, Deoni, S. C, Ecker, C., Happé, F., Henty, J., Jezzard, P., Johnston, P., Jones, D. K, Lombardo, M. V, Madden, A., Mullins, D., Murphy, C. M, Murphy, D. G, Pasco, G., Sadek, S. A, Spain, D., Steward, R., Suckling, J., Wheelwright, S. J & Williams, SC. (2015). White-matter relaxation time and myelin water fraction differences in young adults with autism. Psychological Medicine,45(4), 795-805. United Kingdom: Cambridge University Press. Retrieved from https://doi.org/10.1017/S0033291714001858
Increasing evidence suggests that autism is associated with abnormal white-matter (WM) anatomy and impaired brain ‘connectivity’. While myelin plays a critical role in synchronized brain communication, its aetiological role in autistic symptoms has only been indirectly addressed by WM volumetric, relaxometry and diffusion tensor imaging studies. A potentially more specific measure of myelin content, termed myelin water fraction (MWF), could provide improved sensitivity to myelin alteration in autism. We performed a cross-sectional imaging study that compared 14 individuals with autism and 14 age- and IQ-matched controls. T 1 relaxation times (T 1), T 2 relaxation times (T 2) and MWF values were compared between autistic subjects, diagnosed using the Autism Diagnostic Interview – Revised (ADI-R), with current symptoms assessed using the Autism Diagnostic Observation Schedule (ADOS) and typical healthy controls. Correlations between T 1, T 2 and MWF values with clinical measures [ADI-R, ADOS, and the Autism Quotient (AQ)] were also assessed. Individuals with autism showed widespread WM T 1 and MWF differences compared to typical controls. Within autistic individuals, worse current social interaction skill as measured by the ADOS was related to reduced MWF although not T 1. No significant differences or correlations with symptoms were observed with respect to T 2. Autistic individuals have significantly lower global MWF and higher T 1, suggesting widespread alteration in tissue microstructure and biochemistry. Areas of difference, including thalamic projections, cerebellum and cingulum, have previously been implicated in the disorder; however, this is the first study to specifically indicate myelin alteration in these regions.
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