U.S. Rep Gabrielle Giffords is speaking in full sentences and is making a tremendous amount of progress in her recovery from a brain injury, her doctors in Houston said today.

Doctors said that in the few weeks since Giffords arrived at TIRR Memorial Hermann, the rehabilitation center where she is being treated, she has gone from mouthing words to speaking sentences, saying things like, “I’m tired and want to go to bed.”

Giffords is walking with assistance and is interacting with visitors and the medical staff.

Dr. Gerard Francisco, the head of the team of doctors overseeing Giffords’ rehabilitation, says Giffords is gaining more movement and that the amount of assistance she needs is declining. “We can engage her for a long period of time during therapies, or between therapies,” Francisco said.

Doctors said Giffords’ “upbeat” personality is beginning to show. She is laughing and getting excited when she makes improvement, Francisco said.

Giffords was shot in the head Jan. 8 during a political event on Tucson’s northwest side. Six people were killed and 13 were wounded in the shooting spree.

Doctors addressed reports this week that Giffords is hoping to be at the launch next month of her husband’s space shuttle mission in Florida next month. Mark Kelly will be the commander of Endeavor when it launches in April, and his identical twin brother, Scott, is the current leader of the International Space Station crew.

Kelly has said he hoped Giffords would be able to see him off.

Dr. Dong Kim says doctors still want her to improve enough to attend the launch, but it’s too early to tell.

Kim says they expect to reattach her skull at some point in May. She now wears a helmet that covers her head. He said she can travel before that happens.

Doctors also said they have removed Giffords’ breathing tube, a big step forward in her recovery. Dr Imoigele Aisiku described the tube removal as a “fist-pump” moment.

Giffords does not have any memories of the shooting spree, doctors said, which is expected after an injury to the brain.

The congresswoman’s husband has told her that she was shot Jan. 8, though she doesn’t know about the other victims in the tragedy, Giffords’ spokeswoman C.J. Karamargin confirmed today.

The Associated Press and Star Reporter Stephanie Innes contributed to this report