alleryStart learning →What does functional MRI actually detect when it maps activity in the brain?
AA change in the water content of the blood
BA change in blood flow to active nerve cells
CA change in bone density near active cells
DA change in the electric field of the skull
Answer & Solution
Correct answer: B. A change in blood flow to active nerve cells
1. Nerve cells increase their consumption of oxygen when they are active.
2. Blood haemoglobin releases oxygen to those cells, and it has different magnetic properties when oxygenated than when deoxygenated.
3. Functional MRI measures the change in blood flow that goes with thought, experience and action.
4. The instrument therefore detects a blood oxygen dependent signal rather than any electrical one.
5. Electrical activity of the brain is what an electroencephalogram records instead.
_Source: OpenStax College Physics (CC BY 4.0), Ch 22 "Magnetism", section 22.11 More Applications of Magnetism_
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