Increased white matter metabolic rates in autism spectrum disorder and schizophrenia

Both autism spectrum disorder( ASD) and schizophreniaare often characterized as disorders of white matterintegrity. Multimodal investigations have reported elevated metabolicrates, cerebral perfusion and basal activity in various white matterregions in schizophrenia, but none of these functions has previously been studied in ASD. We used 18fluorodeoxyglucose positron emission tomography to compare white matter metabolicrates in subjects with ASD(n = 25) to those with schizophrenia(n = 41) and healthy controls (n = 55) across a wide range of stereotaxically placed regions-of-interest. Both subjects with ASDand schizophreniashowed increased metabolicrates across the white matterregions assessed, including internal capsule, corpus callosum, and white matterin the frontal and temporal lobes. These increases were more pronounced, more widespread and more asymmetrical in subjects with ASDthan in those with schizophrenia. The highest metabolicincreases in both disorders were seen in the prefrontal white matterand anterior limb of the internal capsule. Compared to normal controls, differences in gray matter metabolismwere less prominent and differences in adjacent white matter metabolismwere more prominent in subjects with ASDthan in those with schizophrenia. Autism spectrum disorderand schizophreniaare associated with heightened metabolicactivity throughout the white matter. Unlike in the gray matter, the vector of white matter metabolicabnormalities appears to be similar in ASDand schizophrenia, may reflect inefficient functional connectivity with compensatory hypermetabolism, and may be a common feature of neurodevelopmental disorders.