Some brains reorganize for better communication after injury from hypertension
Hypertension that leads to vascular dementia in older adults begins to impact the brain by middle age, reports a large new Northwestern Medicine study published in PNAS, the first to show the process begins so early. But in some middle-aged individuals with this damage, their brains reorganize to bypass the damage and enhance communication between brain cells, the study also found. And these people did better on tasks related to cognitive function.
“This tells us some people’s brains appear to compensate by rerouting communication in the brain networks to improve messaging. It’s like creating detours when one route is blocked or clogged,” said senior author Farzaneh Sorond, MD, PhD, the Dean Richard H. Young and Ellen Stearns Young Professor, vice chair for faculty development and education in the Department of Neurology and a Northwestern Medicine neurologist. “If we can develop a treatment to produce this plasticity in an older person’s brain, we might be able to improve their cognition and mobility.”
Not everyone is affected equally by damage to their brain’s white matter as they age, Sorond said.
“Why is that?” Sorond said. “We’ve been asking that for decades. Here we have an important clue. These people with white matter disease in their brain, why are they functioning OK? If we can figure it out, then we can help others.”
In the multi-site study, scientists observed 600 individuals, average age of 55.5 in an fMRI. All had vascular risk factors and were at risk for vascular dementia in late life but currently had normal cognitive function. Scientists looked at the executive function region of their brains, which is one of the first regions affected as people develop age-related white matter injury. This region of the brain is key to working memory and controls planning and decision making.
One form of brain injury from hypertension appears as white splotches, referred to as white matter hyperintensities, on brain fMRIs.
While participants were resting in the fMRI, scientists measured the level of oxygenation across the entire brain. As the brain works, it increases and decreases oxygen in a synchronized manner. The synchronization was enhanced in the people whose brains had redistributed paths to the brain’s executive function region and were able to compensate for the white matter injury.
Next, the participants were given a series of tasks that tested their executive function. Those individuals whose brains had shown increased connectivity and rerouted brain networks performed better on the tasks than those whose brains did not.
The study adjusted for diabetes, cholesterol, BMI (Body Mass Index) and smoking, so scientists only were looking at the effect of blood pressure.
Other Northwestern authors are Donald Lloyd-Jones, MD, ScM, the chair and Eileen M. Foell Professor of Preventive Medicine; Alexander Nemeth, MD, chief of Neuroradiology in the Department of Radiology; Todd Parrish, PhD, professor of Radiology in the Division of Basic and Translational Radiology Research; Carson Ingo, PhD, assistant professor of Physical Therapy and Human Movement Sciences; Lei Wang, PhD, adjunct associate professor of Psychiatry and Behavioral Sciences; Alexandr Kogan, MS; and Sanaz Sedaghat, PhD.
This study was supported by the National Institute of Neurological Disorders and Stroke grant R01-NS085002. The CARDIA study is conducted and supported by awards from the National Heart, Lung, and Blood Institute (NHLBI) in collaboration with the University of Alabama at Birmingham HHSN268201800005I and HHSN268201800007I, HHSN268201800003I and HHSN268201800006I and the Kaiser Foundation Research Institute HHSN268201800004I. CARDIA was also partially supported by the Intramural Research Program of the National Institute on Aging (NIA) and an intra-agency agreement between the NIA and the NHLBI AG0005.