What does fMRI measure to indicate functional differences in the brain?

Functional Magnetic Resonance Imaging (fMRI) is designed to measure changes in blood flow in the brain, specifically focusing on oxygen levels. It capitalizes on the fact that active brain regions require more oxygen; when neurons are more active, they consume more oxygen and the local blood supply increases to meet this demand. This change in oxygenation levels is reflected in the blood’s magnetic properties, allowing fMRI to capture real-time brain activity based on blood oxygenation level-dependent (BOLD) signals.

The BOLD signal is instrumental in highlighting functional differences between brain areas as they respond to various tasks or stimuli, thereby demonstrating cognitive processing and neural activation patterns. This makes oxygen levels a key indicator in identifying functional differences in brain regions during fMRI studies.