WASHINGTON (CNN) -- South Dakota Sen. Tim Johnson is participating in occupational, physical and speech therapy as he continues his recovery from a brain hemorrhage and resulting surgery last month, his office said.

"Just yesterday, he had his tracheotomy removed," said a written statement Friday. "Johnson is making consistent progress in his recovery; however, it is anticipated that his rehabilitation will take several months."

Johnson is working with parallel bars and naming objects as part of his therapy, the statement said. He was transferred out of the intensive care unit at George Washington University Hospital earlier this month.

"Senator Johnson is participating in approximately three hours of physical, occupational and speech therapy a day in our in-patient rehabilitation unit," said Philip Marion, the hospital's director of physical medicine and rehabilitation, in the statement. "His program includes strengthening exercises to gain mobility on his right side."

On Dec. 13, after slurring his speech during a talk with reporters, the 60-year-old Democrat underwent surgery for a hemorrhage inside his brain cavity caused by a hereditary condition in which blood vessels are too close together -- an arteriovenous malformation. Doctors have said the surgery was successful.