blood-oxygen-level dependent (BOLD) signal

The Blood Oxygen Level Dependent (BOLD) signal is a technique used in functional magnetic resonance imaging (fMRI) to measure brain activity. When a specific brain area is active, it requires more oxygen. Because oxygen-rich blood has different magnetic properties than oxygen-poor blood, fMRI can detect changes in blood flow. The BOLD signal reflects these changes, allowing researchers to see which parts of the brain are working during different tasks or thoughts. Essentially, it provides insight into brain function by monitoring how blood and oxygen levels fluctuate in response to neural activity.