High blood pressure is a major risk factor for several diseases, including stroke, heart disease and dementia. In the majority of cases, it is not known what causes high blood pressure. One proposed cause is an increase in the fight-or-flight response of the body. This increase would serve to drive blood pressure up in an effort to maintain blood flow to the brain. The fight-or-flight response is regulated by various parts of the brain. Magnetic resonance imaging (MRI) uses strong magnetic fields to take images of the brain. Functional MRI (fMRI) can be used to investigate changes in neural activity and blood flow to the brain. In this study, we propose to use low frequency fluctuations in the fMRI signal as a marker of vascular function. We will use this to compare the function of the fight-or-flight response between people with and without high blood pressure. This will hopefully lead to a better understanding of the cause of high blood pressure, and ultimately to better treatment of the disease.
