Final answer:
Functional magnetic resonance imaging (fMRI) shows changes in brain activity over time by tracking blood flow and oxygen levels. It provides more detailed images of the brain's structure and better accuracy in time compared to PET scans. MRI and fMRI are often used to compare healthy and diseased brains.
Step-by-step explanation:
In magnetic resonance imaging (MRI), a person is placed inside a machine that generates a strong magnetic field. The magnetic field causes the hydrogen atoms in the body's cells to move. When the magnetic field is turned off, the hydrogen atoms emit electromagnetic signals as they return to their original positions. Tissues of different densities give off different signals, which a computer interprets and displays on a monitor. Functional magnetic resonance imaging (fMRI) operates on the same principles, but it shows changes in brain activity over time by tracking blood flow and oxygen levels.
The fMRI provides more detailed images of the brain's structure, as well as better accuracy in time, than is possible in PET scans. With their high level of detail, MRI and fMRI are often used to compare the brains of healthy individuals to the brains of individuals diagnosed with psychological disorders. This comparison helps determine what structural and functional differences exist between these populations.