What does fMRI measure?

What does fMRI measure?

• A. Changes in brain activity by tracking blood oxygen levels.
• B. Electrical activity of neurons directly.
• C. Brain structure only.
• D. Hormone levels in blood.

Answer: (A)

fMRI measures brain activity indirectly by detecting changes in blood oxygenation. When neurons in a region become active, they trigger a vascular response that increases blood flow to that area. This alters the balance of oxygenated and deoxygenated hemoglobin, producing a detectable signal—the BOLD signal—on MRI. Higher activity in a region leads to characteristic changes in this signal, allowing researchers to infer which areas are more engaged during a task. It’s important to note this is not a direct measure of electrical firing of neurons, and it doesn’t map brain structure (that would be a structural MRI) or hormone levels in the blood.

fMRI measures brain activity indirectly by detecting changes in blood oxygenation. When neurons in a region become active, they trigger a vascular response that increases blood flow to that area. This alters the balance of oxygenated and deoxygenated hemoglobin, producing a detectable signal—the BOLD signal—on MRI. Higher activity in a region leads to characteristic changes in this signal, allowing researchers to infer which areas are more engaged during a task. It’s important to note this is not a direct measure of electrical firing of neurons, and it doesn’t map brain structure (that would be a structural MRI) or hormone levels in the blood.