There has been little research on how chronic pain is related to brain activity. The purpose of this study is to learn more about pain and brain activity by finding any differences in brain activity among people who have moderate to severe chronic pain and a spinal cord injury, those who have a spinal cord injury but do not experience chronic pain, and people who have neither a spinal cord injury nor chronic pain (please note: subjects do not have to have pain to participate in this study). The information we collect will help the investigators get a better understanding of chronic pain.