Blood Oxygen Level Dependent (BOLD) contrast

BOLD contrast, used in MRI scans, detects changes in blood oxygen levels in the brain. When a brain area becomes active, it consumes more oxygen, leading to increased blood flow that brings oxygen-rich blood to that region. Hemoglobin, the molecule in blood that carries oxygen, affects magnetic properties depending on its oxygen level. Oxygen-rich blood appears different on the MRI, creating contrast that highlights active areas. Thus, BOLD imaging indirectly measures brain activity by observing where blood oxygenation changes occur, providing insights into how different parts of the brain function during various tasks.