Imaging techniques used by HMS researchers at McLean Hospital may have pulled back a bit further the curtain that masks our understanding of the brain activity of people diagnosed with schizophrenia. In work published in the September 15 issue of Biological Psychiatry, senior author Dost Öngür, an HMS associate professor of psychiatry at McLean, and colleagues describe myelin and axon abnormalities they found when using magnetic resonance imaging to peer into the brains of individuals with the disorder.
For their study, the researchers enrolled 22 healthy control individuals from the community and 23 individuals diagnosed with schizophrenia who were participating in the hospital’s clinical services. The study’s design called for each group to undergo two types of imaging: magnetic resonance imaging, to measure the levels of particular chemicals in the brain, and magnetization transfer imaging, to detect changes in the degree of myelination in the neural white matter. Myelin, which wraps around nerve cells, helps the cells transmit signals from one part of the brain to another.
Scientists have long known that the brain in schizophrenia has abnormalities in connections between brain regions, and that imaging has suggested that the abnormalities can be traced to the white matter. But until the present study, researchers have not had the tools to pinpoint whether the abnormalities occurred in the nerve cell extensions known as axons or in the myelin sheath around the axons, or both.
When comparing images from the control group with those from the test group, the research team found abnormalities in both myelin and axons in the brains of people diagnosed with schizophrenia: a reduced myelination of white-matter pathways and an increased diffusion of N-acetylaspartate, an amino acid found in neurons. N-acetylaspartate is thought to indicate nerve cell activity.
The findings, say the authors, suggest that the speeds of the signals traveling along myelinated fibers are abnormal in schizophrenia, possibly leading to information processing difficulties and cognitive deficits.