Deviant functional magnetic resonance imaging patterns of brain activity to speech in 2-3-year-old children with autism spectrum disorder

Background: A failure to develop normal language is one of the most common first signs that a toddler might beat 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.