Task dependent prefrontal dysfunction in persons with Asperger's disorder investigated with multi-channel near-infrared spectroscopy

Dysfunction of the prefrontal cortex has been previously reported in individuals with Asperger's disorder. In the present study, we used multi-channel near-infrared spectroscopy (NIRS) to detect changes in the oxygenated hemoglobin concentration ([oxy-Hb]) during two verbal fluency tasks. The subjects were 20 individuals with Asperger's disorder and 18 age- and IQ-matched healthy controls. The relative [oxy-Hb] in the prefrontal cortex was measured during the category and letter fluency tasks. The mean total [oxy-Hb] during the category fluency task did not differ significantly between the groups; however, during the letter fluency task, the mean [oxy-Hb] in persons with Asperger's disorder was significantly lower than that in controls. These results suggested task-relevant or task-specific prefrontal dysfunction in persons with Asperger's disorder.