Autism spectrum disorders are generally described as disorders of brain development that present early in life and whose phenomenology is a manifestation of the cumulative results of an atypical developmental trajectory. However, some children develop an autism-like condition after an extended period of typical development. The most extreme, late-onset cases of this regressive form of autism have been described by the diagnostic category Childhood Disintegrative Disorder (CDD).
In addition to autism, children with CDD have severe to profound intellectual disabilities. The study of CDD represents an opportunity to understand a regressive process that causes autism and intellectual disability in children with normal early development and that is uniquely situated at the intersection of autism, intellectual disability and regression.
Kevin Pelphrey and his colleagues at Yale University focused on late regression and the neural and genetic mechanisms that lead to this regression. This focus allowed the team to not only understand the distinct nature of CDD but also to identify commonalities between CDD and other autism spectrum disorders, thereby parsing the heterogeneity in autism.
The group’s key findings include the identification of a distinct neural-systems-level phenotype of CDD involving less severe dysfunction (relative to low-functioning autism without regression) in the set of brain regions known to be involved in social cognition and social perception. The phenotype is particularly found in the right fusiform gyrus corresponding to the expected location of the ‘fusiform face area,’ a brain region dedicated to processing faces in typically developing individuals. Moreover, individuals with CDD exhibit intact face scanning as measured via eye tracking. They focus on the eyes of faces as much as typically developing individuals do.