Final answer:
The temporal lobe would 'light up' the most on a PET scan when a patient reads a paragraph, as it is involved in language processing and comprehension.
Step-by-step explanation:
If a patient is asked to read a paragraph while undergoing a PET scan, you would expect to see increased activity in specific regions of the brain that are responsible for processing reading and language. In this case, the most active brain region would likely be the temporal lobe, which is involved in processing and interpreting sounds and is critical for understanding language. The temporal lobe houses Wernicke's area, which is essential for the comprehension of speech. Although the frontal lobe is also involved in language, particularly in language production via Broca's area, the task of reading and comprehension is more closely tied to the functions of the temporal lobe.