Abstract
BackgroundDysfunctions of the prefrontal cortex have been previously reported in individuals with autism spectrum disorders (ASD). Previous studies reported that first-degree relatives of individuals with ASD show atypical brain activity during tasks associated with social function. However, developmental changes in prefrontal dysfunction in ASD and genetic influences on the phenomena remain unclear. In the present study, we investigated the change in hemoglobin concentration in the prefrontal cortex as measured with near-infrared spectroscopy, in children and adults with ASD during the letter fluency test. Moreover, to clarify the genetic influences on developmental changes in the prefrontal dysfunction in ASD, unaffected siblings of the ASD participants were also assessed.Methodology/Principal FindingsStudy participants included 27 individuals with high-functioning ASD, age- and IQ-matched 24 healthy non-affected siblings, and 27 unrelated healthy controls aged 5 to 39 years. The relative concentration of hemoglobin ([Hb]) in the prefrontal cortex was measured during the letter fluency task. For children, neither the [oxy-Hb] change during the task nor task performances differed significantly among three groups. For adults, the [oxy-Hb] increases during the task were significantly smaller in the bilateral prefrontal cortex in ASD than those in control subjects, although task performances were similar. In the adult siblings the [oxy-Hb] change was intermediate between those in controls and ASDs.Conclusion/SignificanceAlthough indirectly due to a cross-sectional design, the results of this study indicate altered age-related change of prefrontal activity during executive processing in ASD. This is a first near-infrared spectroscopy study that implies alteration in the age-related changes of prefrontal activity in ASD and genetic influences on the phenomena.
Highlights
Autism is diagnosed on the basis of a triad of behavioral features: impairment of reciprocal social interaction, communication and imagination, and the presence of repetitive and ritualistic behavior
In functional magnetic resonance imaging studies, individuals with autism spectrum disorders (ASD) have abnormalities of hemodynamic responses in the prefrontal cortex associated with spatial working memory [9,10,11], motor inhibition [12] and visuomotor control [13]
Our research group has recently reported that prefrontal activation assessed with 24-channel near-infrared spectroscopy (NIRS) [14] during the letter fluency task was reduced in adults with ASD as compared with healthy adults
Summary
Autism is diagnosed on the basis of a triad of behavioral features: impairment of reciprocal social interaction, communication and imagination, and the presence of repetitive and ritualistic behavior. Relatives of individuals with autism exhibit higher than normal rates of autism-related impairments including language, communication and social behavior, referred to as the broader autism phenotype (BAP) [3,4] These findings provide evidence that there is a heritable component to autism. Our research group has recently reported that prefrontal activation assessed with 24-channel near-infrared spectroscopy (NIRS) [14] during the letter fluency task was reduced in adults with ASD as compared with healthy adults. These prefrontal activation studies present only findings of adults and adolescents with ASD, but not those of children with ASD. To clarify the genetic influences on developmental changes in the prefrontal dysfunction in ASD, unaffected siblings of the ASD participants were assessed
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