Doctors for Prison Fellowship Ministries founder Chuck Colson say he gave them a thumbs-up sign Wednesday evening, four days after surgery to remove clotted blood from the surface of his brain.

Ministry officials say it's a sign that Colson can "hear, process information and execute commands."

"We are seeing hopeful signs of progress with Chuck. We fully trust in our Lord," his wife, Patty Colson, said in a statement

The 80-year-old remains in critical condition in northern Virginia.

Colson's family says they appreciate prayers on his behalf.