Question

which of the following principles underlies the technique of functional magnetic resonance imaging (fmri)?

it rests on the principle that mental activity is associated with changes in glucose levels in the brain.

it rests on the principle that mental activity is associated with changes in the oxygenated blood levels in the brain.

it rests on the principle that mental activity is associated with changes in magnetic fields in the brain.

it rests on the principle that mental activity is associated with changes in hydrogenated blood levels in the brain.

Explanation:

To determine the correct principle of fMRI, we analyze each option:

• The first option refers to glucose level changes, which is related to PET (Positron Emission Tomography) scans, not fMRI.
• The second option: fMRI works based on the BOLD (Blood - Oxygen - Level - Dependent) signal. When a brain area is active, it needs more oxygen, so there are changes in oxygenated blood levels. This matches the principle of fMRI.
• The third option: fMRI does not rely on changes in the brain's magnetic fields in the way described. The magnetic fields in fMRI are from the scanner, not changes associated with mental activity in the brain itself.
• The fourth option: There is no concept of "hydrogenated blood levels" related to fMRI. The relevant factor is oxygenated blood, not hydrogenated blood.

Answer:

B. It rests on the principle that mental activity is associated with changes in the oxygenated blood levels in the brain.