Which neuroimaging technique detects changes in blood oxygenation related to neural activity?

• A. Functional MRI (fMRI)
• B. Structural MRI
• C. Positron Emission Tomography
• D. Diffusion Tensor Imaging

Answer: (A)

This question examines how neural activity is inferred from vascular signals in neuroimaging. The technique that detects changes in blood oxygenation related to neural activity is functional MRI. When a brain region becomes active, neurons require more oxygen, and blood flow to that area increases. This surge overcompensates for the oxygen use, reducing the amount of deoxyhemoglobin, which changes the magnetic properties of blood and leads to a stronger MRI signal in that region. This blood-oxygen-level–dependent, or BOLD, signal reflects functional activity with a slight delay of a few seconds due to the hemodynamic response.

In contrast, structural MRI is about anatomy, not function. PET measures metabolic processes using radioactive tracers, not blood oxygenation changes detected by MRI. Diffusion Tensor Imaging maps the diffusion of water to reveal white matter tracts, not neural activity. Thus, fMRI uniquely tracks the blood oxygenation changes that accompany brain activity.