In the movie The Bourne Legacy, Aaron cross goes to the Philippines in an effort to infect himself with a virus that will make him permanently more intelligent.

His reasoning is that he wasn't the smartest kid on the block before he was genetically enhanced. However on his way to get infected at the lab he starts to zone out like a space cadet as his brain is failing.

Why does this happen?

Wouldn't he just go back to the way he was before versus becoming a vegetable?