How do fMRI and structural MRI differ in what they measure?

How do fMRI and structural MRI differ in what they measure?

• A. fMRI measures functional activity indirectly, while structural MRI measures physical brain structure.
• B. Structural MRI measures functional activity indirectly.
• C. fMRI measures electrical activity directly.
• D. Structural MRI measures brain microstructure with radiation.

Answer: (A)

Functional MRI tracks brain activity by detecting changes in blood flow and oxygenation that occur after neurons fire. This blood-oxygenation level–dependent signal is an indirect indicator of neural activity, and it unfolds over a few seconds due to neurovascular coupling. Structural MRI, in contrast, provides high-resolution images of the brain’s anatomy—its shapes, borders, gray and white matter, and overall structure—without measuring neural activity. It uses strong magnetic fields and radiofrequency pulses, not ionizing radiation, to reveal tissue structure. So fMRI assesses functional changes over time, while structural MRI maps physical brain structure; fMRI does not measure electrical activity directly, and structural MRI does not capture function.

Functional MRI tracks brain activity by detecting changes in blood flow and oxygenation that occur after neurons fire. This blood-oxygenation level–dependent signal is an indirect indicator of neural activity, and it unfolds over a few seconds due to neurovascular coupling. Structural MRI, in contrast, provides high-resolution images of the brain’s anatomy—its shapes, borders, gray and white matter, and overall structure—without measuring neural activity. It uses strong magnetic fields and radiofrequency pulses, not ionizing radiation, to reveal tissue structure. So fMRI assesses functional changes over time, while structural MRI maps physical brain structure; fMRI does not measure electrical activity directly, and structural MRI does not capture function.