The BOLD Signal

The BOLD signal, or Blood Oxygen Level Dependent signal, is a measure used in fMRI scans to track brain activity. When a brain region becomes active, it consumes more oxygen. The body responds by increasing blood flow to that area, bringing more oxygen-rich blood. This change in oxygen levels alters the magnetic properties of the blood, which the fMRI detects as a signal. Essentially, the BOLD signal indicates which parts of the brain are more active at a given moment, allowing researchers to map brain function in real-time.