Boston (CNN) -- Dzhokhar Tsarnaev, the surviving suspect in the Boston Marathon bombings, lies in a hospital with a gunshot wound to the side of his neck, sedated and intubated, sources say.
But he could be brought out of sedation in minutes so he could answer questions from law enforcement officials, doctors tell CNN.
Intubated and sedated patients are often put on "sedation holidays."
Under normal circumstances, doctors use these holidays, which last anywhere from a few minutes to a few hours, so they can ask patients questions to assess neurological and cognitive functioning.
The patients can't talk, since they have a tube down their throats, but they can write.
"They're still pretty out of it on these holidays, pretty confused and sleepy, but they could be able to understand what's being said to them," said Dr. Albert Wu, an internist and attending physician at Johns Hopkins Hospital.
While many patients are groggy during these holidays, others are quite awake and thoughtful.
Tsarnaev, who has been hospitalized since his capture on Friday, has been communicating with officials, two sources told CNN.
"They have been questioning him since yesterday," a senior law enforcement source said. "There is some form of communication between law enforcement and the suspect."
Neither source would divulge what Tsarnaev has been communicating.
Dr. Corey Siegel, a gastroenterologist and professor at Dartmouth-Hitchcock Medical Center, remembers visiting his grandmother in the intensive care unit while she was intubated and sedated.
Fearing she might be dying, he asked her physicians to decrease her sedation so he could have one last conversation with her. She still couldn't talk but she could write on a notepad.
"She woke up in five minutes and had a conversation. It was March, and she told me where her tax materials were so she could file her taxes," Siegel remembers.
After a "sedation holiday" patients are put back under full sedation.
"It's like these patients are asleep," said Wu, a professor of health policy and management at the Johns Hopkins Bloomberg School of Public Health. "They can't hold a conversation. They're really out of it."
Despite the sedation, some patients do respond a bit to what's going on around them.
They might, for example, grunt if a doctor taps them on the shoulder or says their name.
"They might squeeze your hand in response to a command or move their heads to a sound, but they can't answer questions," said Dr. Athos Rassias, associate professor of anesthesia and critical care at Dartmouth.
Doctors sedate intubated patients because it's uncomfortable and painful to have a tube down the throat and a machine forcing air into the lungs.
CNN Chief Political Analyst Gloria Borger contributed to this report.