First, sorry for my almost three-month hiatus. I am back, anyway. A few days ago, I commented on someone in a YouTube video claiming that high-functioning autism and Asperger’s Syndrome are subtly different in other ways than language acquisition. I disagreed based on DSM-IV criteria. However, the DSM-IV can be criticized, and it remains an ongoing debate whether HFA and Asperger’s are distinct.
Yu et al. (2011) did a meta-analysis of neuroimaging studies on people with autism and Asperger’s Syndrome to determine grey matter volume differences. In each of the analyzed studies, Asperger’s or autistic individuals were compared to controls, so the two groups were not directly compared. Note that autism or Asperger’s diagnostic status was determined based on the absence or presence of language delay.
It was found that not only did autistic individuals’ brains differ more from controls’ brains than the Asperger’s brains differed from those of controls, but that different areas within the grey matter were affected. Specifically, the studies on HFA people showed lower volumes in the cerebellum, right uncus, dorsal hippocampus and middle temporal gyrus compared with controls and grey matter volumes greater than in controls in the bilateral caudate, prefrontal lobe and ventral temporal lobe. In Asperger’s Syndrome people, lower grey matter volumes were found in the bilateral amygdala/hippocampal gyrus and prefrontal lobe, left occipital gyrus, right cerebellum, putamen and precuneus. Grey matter volumes were greater in fewer areas than among HFA subjects, including in the bilateral inferior parietal lobule and the left fusiform gyrus. The areas that are dissimilarly affected in Asperger’s versus HFA are not only related to language acquisition. The authors discuss observed differences between Asperger’s and HFA in the light of neuroimaging. They go so far as to speculate that Asperger’s should be considered more similar to schizophrenia on a continuum of neuropsychopathology than should autism.
Yu KK, Cheung C, Chua SE, McAlonan GM (2011), Can Asperger Syndrome Be Distinguished from Autism?: An Anatomic Likelihood Meta-Analysis of MRI Studies. Journal of Psychiatry and Neuroscience, 36(6): 412-421. DOI: 10.1503/jpn.100138.