A new study provides valuable insight into the neuropathology of early autism development by imaging the brains of naturally sleeping toddlers. The research, published by Cell Press in the June 24 issue of the journal Neuron, identifies a brain abnormality observed at the very beginning stages of autism that may aid in early diagnosis of autism and shed light on its underlying biology.

The human brain is split into two separate hemispheres, which are mostly symmetrical in terms of anatomy and function. "In the typical brain, neural activity is correlated across functionally related cortical areas, like those involved in vision, not only during the completion of a task, such as watching a movie, but also in the complete absence of a task, during rest and sleep," explains lead study author Dr. Ilan Dinstein from the Weizmann Institute of Science in Israel. "It has been suggested that the strength of synchronization between functionally related brain areas in the right and left hemispheres may offer a measure of their functional integrity."

Dr. Dinstein and colleagues used functional magnetic resonance imaging (fMRI) to record neural activity in naturally sleeping toddlers with typical development, language delay, and autism and found a specific abnormality in synchronization between two brain areas commonly associated with language and communication. This abnormality was evident in 70% of toddlers with autism, but in only a handful of typically developing toddlers or toddlers with language delay. This is significant because delayed and impaired language capabilities are a defining characteristic of autism, and, although the autistic and language-delayed toddlers exhibited similar reduced language abilities, the reduced neural synchronization was unique to the autistic group.

"Our results suggest that poor neural synchronization is a notable neural characteristic that is evident at the earliest stages of autism development, when toddlers are only beginning to manifest autistic behavioral symptoms, and is related to the severity of those behavioral symptoms," says Dr. Dinstein. "It is also important to note that the ability to measure this characteristic during natural sleep, when subject cooperation is not required, suggests its utility as a possible diagnostic measure to aid growing efforts of identifying autism during infancy."

This study is part of a bigger research initiative carried out by scientists from the Autism Center of Excellence at the University of California, San Diego, headed by Professor Eric Courchesne, and was completed in collaboration with scientists at the Weizmann Institute and Carnegie Mellon University.