When You're In A Coma, This Is What Happens To Your Body

The experience of being in a coma has raised questions about the human brain and body for centuries. Described in various ways since Hippocrates, the phenomenon was once compared to the natural state of being asleep (via Brain). It's no surprise then that the term is derived from the Greek word "koma," which literally translates as "deep sleep." The ancient term for coma originally meant "being struck with violence" and could be likened to the word "stroke."

From a medical point of view, a coma is defined as a state of prolonged unconsciousness, which can be caused by temporary or permanent damage to the brainstem (via StatPearls). The comatose state differs from individual to individual, but there are a few characteristics that show up frequently. Although there have been some major scientific and medical breakthroughs in the understanding of the root cause and mechanisms of coma, it remains somewhat shrouded in mystery (via Qualitative Health Research). So, what actually is going on in the body when it's in a coma?

When a person is in a coma, they're unresponsive to the outside world. It's almost as if consciousness and awareness have been switched off. Scientists suggest that this happens when the brain's reticular activating system (RAS) is damaged — the bundle of nerves that sits at the brainstem and regulates sleep-wake transitions (via Brain). Many studies have shown that a comatose person's brain doesn't exhibit the same patterns of activity observed during wakefulness (via World Journal of Radiology). Despite the existing research, however, substantial gaps remain in coma understanding. The researchers of a 2013 study published in PLoS ONE discovered some brain activity in the hippocampus of an epileptic man in a coma, pointing out that even though the brain isn't functioning normally, it may be undergoing a process of self-healing and preservation.

Research that has looked at the brains of people in vegetative states also detected activity in some regions of the cortex (via Trends in Cognitive Sciences). It's believed that the brain can still respond to external stimulation and sensations such as pain, which appears to activate the primary sensory cortices receiving input from the outside world. However, these areas are disconnected from the higher-order regions involved in awareness.

What makes a coma particularly fascinating is that despite being in a dormant state, many bodily functions continue to work as normal. The comatose person doesn't carry out their usual voluntary actions, and certain abilities such as thinking are suppressed (per MedicalNewsToday). Although they've lost their higher-order brain capacities, such as awareness, cognition, and personality, many automatic functions and reflexes like breathing, swallowing, and circulation, continue to operate by themselves.

Spontaneous movements sometimes occur: The eyes may suddenly open as a reaction to noise, and some people have withdrawal responses to pain, while others can even be seen laughing or grimacing. This ultimately depends on the root cause of the incident and how it's affected different components of the body. As the coma deepens, these responses can diminish or eventually stop entirely (via The New England Journal of Medicine). Some people in comas may need help breathing via a ventilator, according to the Brain Foundation. Almost every patient needs to be tube-fed and hydrated, which is usually done through IV injections.

A coma can certainly look like a state of deep sleep. The person is unaware and unresponsive to what's going on around them. Unlike being asleep, however, a comatose person can't be awoken by external stimuli like sounds or sensations, and doctors and nurses are needed to help the patient stay alive (via The New England Journal of Medicine). While some people in a coma may be partially aware of their surroundings and those in a vegetative state can display some reflex and automatic behaviors, the brain isn't working as if it's in a deep slumber. 

This also means it's unlikely that normal dreams can occur. For instance, damage to the visual and auditory cortex means that visual dreams are lost, as are sounds and voices (via BBC Science Focus). An impaired reticular activating system — which regulates the body's sleep-wake cycle — means that the comatose person can't enter the phase of deep sleep known as rapid-eye-movement (REM), which facilitates dreaming.

You may wonder just how much a person in a coma can hear and comprehend. Reports by those who've recovered from a comatose state suggest that some people can hear voices and even understand what's being said to them (via BuzzFeed). Research tells us that the voices of loved ones recounting a familiar story can help arouse the unconscious brain and speed up recovery for the patient in a coma (via ScienceDaily). 

A 2019 study from Frontiers of Young Minds used electroencephalography (EEG) to measure the neuronal activity of comatose patients as a way to determine how much they could actually hear. The researchers found that, even in a deep coma, the brain is capable of picking up on sounds, like approaching footsteps and bits and pieces of conversations. It appeared that several patients' brains reacted to sounds that were presented as short rhythmic blips, and could even distinguish between the different sounds that were played to them. In fact, they displayed the same pattern of activity as healthy and awake brains. However, the capacity to tell different sounds apart diminished for patients who later passed away, according to the study authors, raising the question of "whether this decreased ability to tell sounds apart was related to the patient's outcome."

Although dreaming is unlikely during a coma, other dream-like states and visions may be possible, according to some researchers (via Business Insider). If the myriad accounts of coma survivors are anything to go by, then strange hallucinations are pretty common. One reason for this is that people in intensive care are given a cocktail of medications, such as opiates, which can trigger intense or disturbing dreams that last for long periods of time (via Healthtalk). 

Dreaming, nightmares, and hallucinations are generally common in the critically ill, and many patients experience distressing dreams despite having had no drugs. Research on dreaming during a coma is hard to conduct, as it's tricky to investigate and understand what the brain goes through while it's unconscious. It is also difficult to determine whether the mental states that people experience are actual dreams or mere hallucinations. What we know relies heavily on the memories and personal accounts of survivors, which can be hard for people to trace back and put into words.

Despite sharing a similar name, a medically-induced coma is somewhat different from a traditional coma. Physicians can medically induce a coma using anesthetic drugs, such as propofol or a barbiturate, to shut down or minimize brain activity, putting the brain into temporary hibernation (via PLoS Computational Biology). Patients who are intentionally put into a coma are usually at high risk of brain injury due to a life-threatening illness, physical trauma, or drug overdose. The procedure reduces blood flow and slows down the brain's metabolism in order to prevent swelling and inflammation, which can starve the brain of oxygen and cause permanent damage. A medically-induced coma gives the brain some time to rest and heal. The procedure is usually administered using an infusion pump, and the length of time that a patient is kept in the coma is largely dependent on the cause and severity of their condition.