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We don't know what Michael Schumacher might remember from the time he spent in an induced coma, but we do know that other people in similar circumstances have had strange experiences.
People sometimes report strange memories, dreams, or even visions from the time they spend in a coma. But how much do we know about what they experience or are aware of during that time?
In order to piece that together, according to Dr. Alex Proekt, an assistant professor of anesthesiology at Weill Cornell Medical College in New York, we first have to try to understand what it means to be unconscious.
What It Means To Go Under
After a person suffers serious head trauma, doctors have little time to spare. The brain swells up in response to injury, sometimes pushing against the skull or cutting off oxygen to certain parts, which can cause brain damage or even death.
In some cases, the only response is the drastic step of putting someone into a medically induced coma. Shutting down or limiting brain activity by inducing a coma reduces blood flow and the brain's metabolic rate, which helps reduce swelling. This allows the brain to rest and provides time for it to heal.
The latest high profile case of this sort is that of Formula One legend Michael Schumacher. After a helmet-splitting skiing accident, Schumacher was airlifted to Grenoble University Hospital Center on December 30, 2013. No one knew if he would even survive. His injuries were so severe that doctors immediately put him into an induced coma.
Although they share a name, a medically-induced coma is drastically different from a traditional coma caused by trauma, according to Proekt. Intentionally putting someone into a coma is like putting them under anesthesia — they become unconscious, but crucially, we know how to wake them up.
On Monday, June 16, a spokeswoman for Schumacher announced that he was awake and had left the hospital. While we don't know much about his recovery yet or what he will remember — the spokeswoman said he will "continue his long phase of rehabilitation" — we do know that doctors began the process of bringing him out of the coma in February. That waking process is complicated and involves the mind traveling through a series of different mental states that we are just starting to understand.
What It Means To Wake Up
There's no binary between unconscious and awake. Just as traditional sleep has various stages, like slow-wave sleep and R.E.M. sleep, there are different brain states that the mind can register while unconscious and different states that the brain enters while waking up.
The brain doesn't just go from "less conscious" to "more conscious," according to Proekt. There are ups and downs along the way.
In a true, or non-induced coma, there's no evidence of fluctuating circadian cycles or changing brain activity, according to Proekt. In that case, he says it's highly unlikely anyone would remember anything or even dream — though if they wake up, which isn't guaranteed, they might enter mental states along the way that allow them to dream.
Since we don't know what steps someone's mind goes through as they wake from a true coma, they might still appear to be in a coma when they are actually waking up, and at some point might become partially aware of their surroundings at that time.
When a doctor puts a patient into a medically induced coma, meanwhile, they are trying to create a mental state that will minimize brain activity, and usually, the patient's consciousness or perception of the world around them. However, a person's brain could spend time in more active states while coming into or out of the induced coma, just like when people go under anesthesia.
In some cases, people receiving ordinary anesthesia may spend time in stages that allow for experiences similar to dreams. In rarer cases, they may not go as far under as they should, and may have memories of something happening around them. While highly uncommon, Proekt says that one or two people out of 1,000 might actually remember what's happening around them during surgery.
'Remembering' What Was Never There
More commonly, people remember things that never happened.
It's hard to characterize the different mental experiences that people have while in a coma. Some of them may be dreams, others are hallucinations.
In the comments section of a Scientific American article about medically induced comas, people started to share some of what they remember of the experience. Though it's not possible to verify these reports, they show some of the crazy journeys the mind takes while unconscious or in the process of waking.
Many are scary.
One commenter, Biconderopus, writes:
It was one ongoing nightmare that I couldn't awake from... It took me MUCH longer to heal from the imagery in that coma than it did from the physical injuries.
Commenter koko11 had a similar experience:
In July 2009 I was in induced coma due to H1N1 virus coupled with Legionnaire's Disease which led to my body going into Sceptic Shock. [sic]
Like many of you, I have also experienced nightmares that seemed unbelievably vivid and detailed. It took me a few days after I was woken up to realise that they are not real.
For a while I had no "live" memories of how I have ended up in hospital even though I was told.
Certain things people said around me while in coma also got incorporated into the nightmares but with some changes.
It was more difficult to get over the nightmares than to recover physically.
There's even a neurosurgeon who claims he experienced the divine while in a coma. He became convinced that heaven was real (and wrote a bestselling book about it). While it's hard to say exactly what someone is experiencing in this state of mind, others have questioned the doctor's story, with vivid hallucination as the most probable explanation for what he recalled.
Where These Strange Visions Come From
The brain can interpret what it experiences in many ways, and people often hold onto whatever explanation makes the most sense or is the most convenient for them. Since we're just beginning to understand the path the mind follows when it goes from unconscious to awake, we don't know exactly why some people end up in states that provide these visions, nightmares, and in rare cases, memories.
Proekt says that in many ways, these are likely the consequences of our brains trying to clarify or codify representations of a barely felt outside world.
Dr. Michael J. Souter, professor of anesthesiology and neurological surgery at the University of Washington in Seattle, told LiveScience that people experience these "vivid nightmares" and "disturbing hallucinations" perhaps because their brain is trying to make sense of the sounds around them.
Given what we know about his case, could Schumacher have some memory of his time in the hospital, or could he have experienced a vision, dream, nightmare, or hallucination?
With the caveat that it's especially hard to say what's happening in a brain that's gone through trauma, Proekt says "it's possible."
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