Is there a known correlation between brain activity and disease (e.g pancreatic cancer and brain activity)?

Clarify? Not really: Not sure exactly what you're asking. Pancreatic cancer itself does not usually affect the brain, and I am not aware of any brain conditions that increase risk for pancreatic cancer. But certainly many cancer treatments, pain relievers, and just being ill can all affect mood, mind and mental acuity. The brain is a very complex organ, so a more detailed question may help us answer you better.

Myths: There is a "pop" notion that bad attitudes cause cancer. This is both totally false and cruel. Advanced cancer of most sorts may produce chemicals that slow brain activity and cause fatigue, and rarely the immune response to a tumor will attack the brain, though this almost never happens with pancreatic cancer.