HOUSTON – Doctors will replace a piece of U.S. Rep. Gabrielle Giffords’ skull with a plastic implant today, another encouraging step in the Arizona congresswoman’s recovery from a gunshot to the head more than four months ago.

The surgery — coming just days after Giffords traveled to Florida to watch her astronaut husband launch into space — was confirmed to The Associated Press by a person familiar with the congresswoman’s care. The person spoke on condition of anonymity because the information has not officially been released.

Doctors removed a piece of Giffords’ skull to allow room for brain swelling shortly after a would-be assassin shot her in the head Jan. 8, critically wounding her, and also killed six people and injured 12 others at a political event in her hometown of Tucson, Ariz.

Dr. Richard Riggs, chair of physical medicine and rehabilitation at Cedars-Sinai Medical Center in Los Angeles, said the surgery to place the plastic implant is relatively simple. Recovery is short — a day or two at the most — and is mostly from the effects of anesthesia, he said. Riggs is not involved in Giffords’ care.