[Hemodynamic activities in children with autism while imitating emotional facial expressions: a near-infrared spectroscopy study].

OBJECTIVE: To examine the hemodynamic activities in the frontal lobe, children with autistic disorder and matched controls underwent near-infrared spectroscopy (NIRS) while imitating emotional facial expressions. METHODS: The subjects consisted of 10 boys with autistic disorder without mental retardation (9 - 14 years) and 10 normally developing boys (9 - 14 years). The concentrations of oxyhemoglobin (oxy-Hb) were measured with frontal probes using a 34-channel NIRS machine while the subjects imitated emotional facial expressions. RESULTS: The increments in the concentration of oxy-Hb in the pars opercularis of the inferior frontal gyrus in autistic subjects were significantly lower than those in the controls. However, the concentrations of oxy-Hb in this area were significantly elevated in autistic subjects after they were trained to imitate emotional facial expressions. The increments in the concentration of oxy-Hb in this area in autistic subjects were positively correlated with the scores on a test of labeling emotional facial expressions. CONCLUSIONS: The pars opercularis of the inferior frontal gyrus is an important component of the mirror neuron system. The present results suggest that mirror neurons could be activated by repeated imitation in children with autistic disorder.