Autism can be difficult to spot in young children, and currently parents must rely on behavioral evaluations for diagnosis. But a new study offers hope that a simple electroencephalogram (EEG), which measures the electrical activity of the brain, can give doctors a reliable tool to diagnose autism as early as infancy.
Scientists at Boston Children's Hospital compared the EEG measurements of more than 1300 children with and without autism. They examined the extent to which electrical activity from various brain regions synchronized with activity from other regions, known as EEG coherence, or connectivity. A trend emerged: Compared with the control group, the children with autism had reduced connectivity between brain regions, and this was especially true in regions of the brain's left hemisphere that are responsible for language.
To measure connectivity in the brain, researchers Frank Duffy and Heidelise Als quantified the degree to which any two given EEG signals—in the form of waves—are synchronized. If two or more waves rise and fall together over time, those brain regions are tightly connected.
Duffy and Als generated coherence readings for more than 4000 unique combinations of electrode signals and, using computational analysis, looked for the signals that seemed to vary the most from child to child. From these, they identified 33 coherence factors that consistently distinguished the children with autism.
Previous studies using EEG and functional MRI to study autism have found that people with autism often have altered connectivity across brain regions compared with people without autism. But the details of these studies, such as how the connectivity is altered, have differed in conflicting ways. Consequently, scientists haven't been able to come up with reliable criteria for EEG- or MRI-based diagnostic tests.
The new study attempted to clear up some of the confusion. The study is the largest and most rigorous of its kind to date. The researchers also took special care to minimize the effects of EEG artifacts: non-relevant electrical activity generated by the blinking, eye movement and bursts of muscle activity of squirmy kids.
Duffy and Als say they believe the findings could be the basis for a future diagnostic test of autism, particularly at very young ages, when behavior-based measures are unreliable. The researchers plan to repeat the study for children with Asperger's syndrome to see if EEG patterns are similar to those of autism.
The study was published June 26 in the journal BMC Medicine.
Image credit: Frank Duffy and Heidelise Als, Boston Children's Hospital