Overview and Implications
A large portion of neuroscience research focuses on the relationship between the structure and function of the nervous system while also taking into account environmental influences on brain organization. Specifically within autism research, previous studies have shown abnormal structural organization in infant brains may lead to decreased neural plasticity and specialization, which may eventually affect environmental responsiveness in later years of life (Blasi et al., 2011). Thus, many studies attempt to characterize the differences between typical and atypical brain development in children with and without autism.
Wolff et al. conducted a longitudinal study examining the development of 15 white matter fiber tracts by analyzing the fractional anisotropy (FA) values and trajectories of children at high risk for autism. The study found that children who eventually went on to develop autism (ASD-positive group) typically started out with higher FA values at 6 months followed by blunted trajectories over the next 18 months than children who did not develop autism (ASD-negative group).
These findings are significant in enhancing our understanding of the development of autism since they suggest that abnormal development of white matter in the brain may be a precursor to the manifestation of symptoms of autism in later years of life. Furthermore, the statistically higher FA values of the ASD-positive group at 6 months may lead to the development and understanding of a biomarker for autism with future research.
In addition to its large sample size, which adds to the credibility of its findings, this study is extremely thorough since it provides both cross-sectional and longitudinal analyses of the development of white matter in the brain. The longitudinal nature of the data allows us to characterize the dynamic relationship between brain development and behavioral symptoms of autism.
Although this study is strong for its time, modern studies in autism now use a more conservative approach. For example, the study classified the ASD-positive and negative groups based on the Autism Diagnostic Observation Schedule and Mullen Scales of Early Learning Assessments. However, now, most studies classify these groups based on DSM-IV criteria, which are usually more accurate. Furthermore, since 2012, our understanding of white matter structure has increased greatly, and the current atlas now lists 22 white matter fiber tracts, rather than only the 15 looked at in this study.
Future studies may expand to look at including both high risk and low risk children for autism when studying the development of white matter fiber tracts. Since the present study only looks at high-risk children, its findings cannot be generalized to all children, and it is possible that the higher FA trajectory in the ASD-negative group was due to some type of developmental resilience to familial risk for autism rather than reflecting the trajectories of all neurotypical children.
Blasi, A., Mercure, E., Lloyd-Fox, S., Thomson, A., Brammer, M., Sau- ter, D., Deeley, Q., Barker, G.J., Renvall, V., Deoni, S., Gasston, D., Williams, S.C., Johnson, M.H., Simmons, A., & Murphy, D.G. (2011). Early special- ization for voice and emotion processing in the infant brain. Curr Biol, 21, 1220–1224
Wolff, J.J., Gu, H., Gerig, G., Elison, J.T., Styner, M., Gouttard, S., Botteron, K.N., Dager, S.R., Dawson, G., Estes, A.M., Evans, A.C., Hazlett, H.C., Kostopolous, P., McKinstry, R.C., Paterson, S.J., Schultz, R.T., Zwaigenbaum, L., & Piven, J. (2012). Differences in White Matter Fiber Tract Development Present From 6 to 24 Months in Infants with Autism. Am J Psychiatry, 169, 589-600.