BACKGROUND

A failure to develop normal language is one of the most common first signs that a toddler might be at risk for autism. Currently the neural bases underlying this failure to develop language are unknown.

METHODS

In this study, functional magnetic resonance imaging (fMRI) was used to identify the brain regions involved in speech perception in 12 2-3-year-old children with autism spectrum disorder (ASD) during natural sleep. We also recorded fMRI data from two typically developing control groups: a mental age-matched (MA) (n = 11) and a chronological age-matched (CA) (n = 12) group. During fMRI data acquisition, forward and backward speech stimuli were presented with intervening periods of no sound presentation.

RESULTS

Direct statistical comparison between groups revealed significant differences in regions recruited to process speech. In comparison with their MA-matched control subjects, the ASD group showed reduced activity in an extended network of brain regions, which are recruited in typical early language acquisition. In comparison with their CA-matched control subjects, ASD participants showed greater activation primarily within right and medial frontal regions. Laterality analyses revealed a trend toward greater recruitment of right hemisphere regions in the ASD group and left hemisphere regions in the CA group during the forward speech condition. Furthermore, correlation analyses revealed a significant positive relationship between right hemisphere frontal and temporal activity to forward speech and receptive language skill.

CONCLUSIONS

These findings suggest that at 2-3 years, children with ASD might be on a deviant developmental trajectory characterized by a greater recruitment of right hemisphere regions during speech perception.