Which statement correctly pairs fMRI with its primary measurement?

Which statement correctly pairs fMRI with its primary measurement?

• A. fMRI measures brain activity through blood oxygenation
• B. fMRI measures brain structure
• C. fMRI measures brain metabolism
• D. fMRI measures neurotransmitter levels

Answer: (A)

fMRI centers on measuring brain activity by detecting changes in blood oxygenation, using the BOLD signal. When a brain region becomes active, blood flow increases more than the needed oxygen, shifting the balance of oxyhemoglobin and deoxyhemoglobin. These two forms of hemoglobin have different magnetic properties, so their changing ratio alters the MR signal that the scanner picks up. This makes it possible to infer which areas are more active during a task. It’s an indirect measure tied to neural activity through neurovascular coupling and includes a slight delay due to the hemodynamic response. It does not directly measure brain structure, metabolism, or neurotransmitter levels, which is why this statement about blood oxygenation best captures what fMRI measures.

fMRI centers on measuring brain activity by detecting changes in blood oxygenation, using the BOLD signal. When a brain region becomes active, blood flow increases more than the needed oxygen, shifting the balance of oxyhemoglobin and deoxyhemoglobin. These two forms of hemoglobin have different magnetic properties, so their changing ratio alters the MR signal that the scanner picks up. This makes it possible to infer which areas are more active during a task. It’s an indirect measure tied to neural activity through neurovascular coupling and includes a slight delay due to the hemodynamic response. It does not directly measure brain structure, metabolism, or neurotransmitter levels, which is why this statement about blood oxygenation best captures what fMRI measures.