Jan. 26, 2011 -- Rep. Gabrielle Giffords was moved to a brain rehabilitation hospital today after doctors upgraded her condition from serious to good late Tuesday night.
"She's done remarkably well," said Dr. John Holcombe, Giffords' trauma surgeon.
The fluid accumulation in her brain that concerned doctors over the weekend already has begun to subside, and the drain inserted into her head last week was removed on Monday. Her doctors said there are no signs of infection.
"Since Gabby arrived last Friday, we have noticed daily improvements in her neurological condition," Dr. Dong Kim, a neurologist treating Giffords, said at a press conference this afternoon in Houston. "In terms of recovery for brain issues, this is really at lightning speed."
Watch "World News With Diane Sawyer" for more on this story tonight on ABC.
Giffords' doctors have expressed confidence that she has passed the most critical period for complications, and she already is undergoing physical, occupational and speech therapy. The therapy sessions that began while Giffords was in the ICU will continue and intensify at her new hospital, TIRR Memorial-Hermann, which specializes in brain injuries.
The congresswoman is awake for most of the day, doctors said, and she's able to interact with others and follow commands. Doctors said that while she has been left weakened by her injury, physical therapy will help to strengthen her body and maintain her range of motion. Doctors have begun the process of removing her tracheotomy, and Giffords now is able to breathe and swallow completely on her own.
Giffords' doctors would not predict whether the congresswoman will be able to speak again, but Dr. Kim said, "Her speech function along with everything else has been improving quite a bit."
Congressional Colleagues Honor Giffords at State of the Union
Meanwhile, at Tuesday night's State of the Union address, members of both political parties were wearing black and white ribbons in a show of solidarity with Giffords and the people of Tucson. In a special gesture, her friends in Congress left one seat unfilled.
"There is going to be a chair left empty to symbolize what we all know will be a triumphant return to the House of Representatives when she comes back to us full strength," said Giffords' friend and colleague, Rep. Debbie Wasserman Schultz, D-Fla.
In Houston, Giffords' husband, NASA Commander Mark Kelly, watched tonight's State of the Union Address from his wife's bedside at the hospital. While he keeps watch over her care, the clock is ticking on a critical decision. Kelly has said he will decide within two weeks whether he will command the space shuttle Endeavor's final mission in April.
"Obviously, Mark has trained with this crew for over a year, and so he is the ideal person," NASA Chief Astronaut Peggy Whitson said.
Over the weekend, doctors inserted a small drain in Giffords' skull to remove the brain fluid that had delayed her transfer out of ICU. Experts say it is not uncommon for someone suffering a traumatic brain injury to have such fluid accumulation, caused when the brain bleeds or swells.
"Pressure built up perhaps too quickly for the brain to accommodate," said Dr. Jonathan Fellus, who specializes in brain injury at the Kessler Institute for Rehabilitation in New Jersey.
Fellus said that when left untreated, fluid can be deadly for brain injury patients.
Giffords was brought by a specially equipped private plane from Tucson to Houston's Hobby Airport last Friday and immediately was transported to the Texas Medical Center's intensive care unit by medical helicopter.
Kelly, Doctors Share Details of Gabrielle Giffords' Progress
Before departing for Houston Friday morning, Giffords left the Tucson, Ariz., hospital where she had been treated since suffering a gunshot to her head in an attack over two weeks ago. She was the last shooting victim to leave the hospital.
Along her roughly 10-mile route to the Air Force base, crowds of supporters stood on the curb, cheering and waving flags and signs as her motorcade passed by. Giffords' ambulance was escorted by a squadron of military veterans on motorcycles.
"We could hear applause in the ambulance with Gabby, and she responded very well to that, smiling and even tearing a little bit," said Dr. Randall Friese, one of the doctors who treated Giffords in Tucson. "It was very emotional and very special."
At a press conference in Houston late Friday afternoon, Giffords' medical team said that the trip went flawlessly and that while she has a long road ahead, she has great potential for rehabilitation.
Giffords' husband, Kelly, who lives in Houston, said last Thursday that she soon would be "back at work" and predicted she would be walking around in a couple of weeks.
"I'm extremely hopeful that Gabby will make a full recovery," he said. "She is a fighter like nobody else I know."
In other signs of progress, Giffords was taken outside Thursday for the first time since the attack so she could get some sunlight. She stood up Wednesday for the first time with assistance and looked out of a hospital window.
Giffords already has been able to scroll through an iPad, one of many steps described by her doctors as "fantastic achievements forward."
The Associated Press contributed to this report.