Even a single concussion can cause long lasting disruption to networks within the brain, new research shows. In a small study comprising 20 people with diagnosed concussion and the same number of controls a team led by Benjamin Dunckley in Toronto, Canada, measured brain function using magnetoencephalography (MEG). Because symptoms of concussion such as amnesia, disorientation and confusion are thought to be the product of physical injury in the brain, Dunckley and his colleagues looked for neurophysiological differences between the concussed and uninjured volunteers. They found distinct differences in a combination of brain regions collectively called the default mode network (DMN). This network links several brain regions that exhibited closely correlated activity states when a person’s mental state is not focused on anything in particular.
Activity in the DMN is associated with introspection and daydreaming. Dunckley’s team found significantly increased connectivity between DMN components in concussed volunteers, compared to the controls. Dunkley and his colleagues write that “the data suggest even a single concussion can perturb the intrinsic coupling of functionally-specialised networks in the brain and may explain persistent and wide-ranging symptomatology.”