Objectives: To examine whether microglial activation is increased in individuals with ASD, and whether characteristics of anatomical distribution of the increased, if any, activation of microglia in the brain are different between ASD and controls.
Methods: Twenty adult males with ASD (age range, 18-31 years; mean [SD] IQ, 93.7 [19.0]) and 20 age- and IQ-matched healthy males as control. Diagnosis of ASD was made by the Autism Diagnostic Observation Schedule and the Autism Diagnostic Interview-Revised. Positron emission tomography using a radiotracer [11C](R)-PK11195 was undertaken in each participants. Regional brain [11C](R)-PK11195 binding potential (BP) was estimated by simplified reference tissue model and regarded as a representative measure of microglial activation.
Results: [11C](R)-PK11195 BP was significantly higher in multiple brain regions in adults with ASD as compared to controls (P < .05, corrected). The brain regions with increased binding potentials included the cerebellum, midbrain, pons, superior temporal and fusiform gyri, and anterior cingulate and orbitofrontal cortices. The most prominent increase was observed in the cerebellum and brainstem. The regional patterns of activated microglia in the different brain areas are regarded to be essentially similar between ASD and control groups.
Conclusions: Excessive microglial activation was present in multiple brain regions in ASD, especially in the cerebellum and brainstem. The similar parallelism of the pattern of distribution of activated microglia in both ASD and control groups suggest that activated microglia in ASD, as those in controls, are embryonic or fatal origin.
See more of: Brain Imaging: fMRI-Social Cognition and Emotion Perception
See more of: Brain Structure & Function