Final answer:
The best indicator of brain function is functional magnetic resonance imaging (fMRI), which measures changes in brain activity by generating a map of the most active areas in the brain.
Step-by-step explanation:
The best indicator of brain function is functional magnetic resonance imaging (fMRI). This technique measures changes in brain activity by generating a map of the most active areas in the brain. It uses the change in blood flow as an indicator of neural activity, allowing researchers to study various regions of the brain and their functions.