Sen. Tim Johnson has been conscious at times since his emergency brain surgery last week, his spokeswoman said Monday. But he is being sedated so that he can rest.
The South Dakota Democrat has made it through the crucial first 72 hours since the brain surgery, spokeswoman Julianne Fisher said, a benchmark that doctors consider a good sign for recovery.
The 59-year-old senator remains in critical but stable condition, she added.
Fisher said the next "target" for doctors was to watch his progress over the next week.
The senator showed some signs of recovery late last week, responding to voices, opening his eyes and moving his limbs. But his long-term prognosis is still unclear.
Johnson's sudden illness, due to a congenital blood vessel defect, has raised questions about the Democratic Party's one-vote majority in the upcoming Senate session. South Dakota's Republican governor, Michael Rounds, would appoint a replacement if Johnson's seat were vacated by his death or resignation.
A Republican appointee would create a 50-50 tie and allow the GOP to retain Senate control because of Vice President Dick Cheney's tie-breaking vote.