Which method is commonly used to study brain activity by measuring changes in blood flow?

Functional Magnetic Resonance Imaging (fMRI) is commonly used to study brain activity by detecting changes in blood flow. This technique is based on the principle that when an area of the brain is more active, it requires more oxygen. To meet this demand, blood flow to that area increases, leading to a change in the ratio of oxygenated to deoxygenated hemoglobin. fMRI uses magnetic fields and radio waves to measure these changes in blood oxygen levels, which can be mapped to show active regions of the brain during various tasks or stimuli.

Unlike other methods such as EEG, which measures electrical activity, or CT, which provides structural images without directly assessing functionality, fMRI is specifically designed to capture both the structure and the functioning aspects of the brain in real-time. PET also measures metabolic activity through radioactive tracers but does not have the same temporal resolution as fMRI and is generally more invasive. Thus, fMRI is particularly favored for its ability to provide detailed insights into brain function while being non-invasive.