Which data collection method tracks changes in blood oxygenation to infer neural activity?

• A. EEG
• B. fMRI
• C. MEG
• D. PET

Answer: (B)

Functional magnetic resonance imaging tracks changes in blood oxygenation to infer neural activity. This relies on the BOLD signal: when a brain region becomes active, blood flow increases more than the tissue’s oxygen use, altering the ratio of oxygenated to deoxygenated hemoglobin. These changes affect the MR signal, letting us map where activity occurs with good spatial detail. The trade-off is timing—the vascular response lags neural activity by a few seconds, so temporal resolution isn’t as tight as electrical measures. It’s noninvasive and doesn’t involve radiation. Other methods measure electrical activity directly on the scalp or via magnetic fields (EEG/MEG) with excellent temporal precision but poorer spatial localization, or use radioactive tracers to assess metabolism (PET), which doesn’t reflect oxygenation changes in the same way.