Which imaging technique registers blood flow to functioning areas of the brain?

• A. MRI
• B. fMRI
• C. CT
• D. EEG

Answer: (B)

Functional MRI registers blood flow to functioning areas by measuring the blood-oxygen-level dependent signal. When a brain region is active, it receives more blood flow, changing the balance between oxygenated and deoxygenated hemoglobin. This change alters the MRI signal, producing a map of which areas are involved during a task. This approach differs from structural MRI, which images anatomy; CT, which uses X-rays for structural imaging; and EEG, which records electrical activity with limited spatial precision and doesn’t directly measure blood flow. The strength of fMRI lies in linking functional activity to vascular responses with good spatial localization, though the signal reflects a slight delay after neural activity due to the hemodynamic response.