Question

phantom pain can occur even when atypical signals from the peripheral nervous system are blocked. so, many scientists think that the central nervous system can contribute to phantom pain. which step would best help scientists understand how the central nervous system contributes to phantom pain? scientists could study the sensory nerves of patients after they have a limb amputated. scientists could examine the brains only of patients who have not had phantom pain after an amputation. scientists could look for differences in the brains of patients before and after they have amputations.

Explanation:

To understand how the central nervous system contributes to phantom pain (when peripheral signals are blocked), scientists need to observe changes in the central nervous system (brain) related to the amputation event. Comparing the same patients' brains before and after amputation isolates the effect of the amputation on the central nervous system, directly linking changes to phantom pain development. The other options either focus on peripheral nerves (not central) or non-amputated patients (who don't experience phantom pain from an amputation).

Answer:

Scientists could look for differences in the brains of patients before and after they have amputations.