Cardinal Jean-Marie Lustiger told the weekly Le Journal Du Dimanche that the pope's mind remains intact.
"We know that his illness is causing progressive paralysis of the body but his mind remains intact. This man, who was an athlete, is becoming more and more a prisoner in his body," Lustiger was quoted as saying.
He said that the pope "retains a spiritual strength, an intellectual capacity and a memory, which are extraordinary for someone who will be 80 next month."
The pontiff, who offered wishes for peace in an Easter ceremony on Sunday, suffers from hand and head tremors, associated with Parkinson's disease, a progressive neurological disorder. He also has difficulty walking due to hip surgery six years ago.