Editors' ChoiceNeuroscience

The Autistic Brain: Out of Synch?

Science Translational Medicine  06 Jul 2011:
Vol. 3, Issue 90, pp. 90ec104
DOI: 10.1126/scitranslmed.3002830

Abstract

Much like the coordinated efforts of musicians in a symphony, different structures in the brain often synchronize for maximal effect. But in patients with neuropsychiatric disorders, neural regions can get out of synch with each other. Dinstein et al. now show that neural synchronization is disrupted in toddlers with autism, which has implications for both diagnosis and pathogenesis.

Autism is a growing public health concern that is characterized by impaired social interactions and language difficulties that manifest in the first years of life. Dinstein and colleagues used functional magnetic resonance imaging (fMRI) to study 29 toddlers with autism, an additional 13 with language delay, and 30 healthy controls. But how does one keep a toddler still for neuroimaging? The answer: Wait for them to sleep. The authors found that the children with autism showed weaker correlations of neural activity between the left and right hemispheres in the inferior frontal and superior temporal gyri, two areas involved in language production and comprehension. Furthermore, the subjects could be classified according to the correlation of these regions across hemispheres, yielding a diagnostic criterion for autism with a sensitivity of 72% and specificity of 84%. Lastly, the strength of interhemispheric synchronization varied inversely with autism severity—the weaker the correlation, the worse the disease state.

This work may have uncovered an early marker of autism that could be used for diagnosis. That this marker may be specific is suggested by the fact that the toddlers with language delay did not show the desynchronization. Furthermore, the study is consistent with other findings of reduced resting-state synchronization in autistic adolescents and adults, pointing to a common neural signature across lifespan. Nevertheless, several questions remain. First, imaging during sleep—although practical for toddlers—is confounded by the dramatically different neural states of rapid eye movement and slow wave sleep. Future studies could incorporate electrophysiologic recordings to control for changes in functional connectivity during these sleep stages. Second, the study cannot yet address the question of association versus causation; further work is required to determine whether reduced synchronization is the etiology of autism or simply a co-occurring marker. In the meantime, the study of Dinstein et al. reveals an important and early neural correlate of autism that may aid diagnosis and provide new therapeutic endpoints.

I. Dinstein et al., Disrupted neural synchronization in toddlers with autism, Neuron 70, 1218–1225 (2011). [Abstract]