Developmental changes in prefrontal cortex activation in children with or without autism spectrum traits on near-infrared spectroscopy

Background: Autism spectrum disorder (ASD) ranges from mild to severe symptoms, with autistic traits possibly distributed throughout the population. However, the precise neurodevelopmental differences in children with autistic traits remain unknown. Subjects and methods: Fifty-three healthy volunteers (32 male and 21 female, mean [standard deviation] age: 12.9 [2.5] years) having a normal intelligence quotient and without social impairment were divided into two groups according to scores of the Pervasive Developmental Disorders Autism Society Japan Rating Scale (PARS). Subjects with or without autistic traits were placed into the high-PARS (n = 14) or low-PARS (n = 39) group, respectively. Activation of the prefrontal cortex was estimated using change in hemoglobin oxygenation concentration (Delta[oxy-Hb]) on near-infrared spectroscopy (NIRS) during a verbal fluency test. Age-related changes in prefrontal cortex activation were first assessed for each group. Then, the effects of age (elementary school age or junior/senior high school age) and PARS score on Delta[oxy-Hb] in the task were analyzed by two-way analysis of variance. Results: We observed significant positive correlations between mean Delta[oxy-Hb] and age in the prefrontal cortex region in the low-PARS group. Mean Delta[oxy-Hb] in the low-PARS group was significantly higher than in the highPARS group. Task performance results were comparable between the groups. Conclusion: In PARS-determined typically developed children, prefrontal cortex activation on NIRS correlated positively with age. In healthy volunteers without ASD but harboring autistic traits, prefrontal cortex activation was markedly lower than in normal counterparts. Our results provide biological evidence that ASD may be a pervasively distributed disorder.