The near-death experiences of patients with locked-in syndrome

Near-death experiences are still partly shrouded in mystery. Mystical explanations aside, researchers from the University of Liège’s Coma Science Group and Liège CHU are attempting to elucidate the physiological and psychological processes likely to explain how they occur and how ‘experiencers’ experience them. In an article recently published in Consciousness and Cognition, they show that the emotions reported by patients with locked-in syndrome who have had a near-death experience, are less positive than those of other experiencers, but their autobiographical memories are richer.

Near-death experiences (NDE) are relatively frequent, with approximately 10 % of people having survived cardiac arrest reporting them. In addition, some people say they have had a NDE even though their life wasn’t in danger and they didn’t go through a period of coma at any moment. Hence, a syncope or extreme stress (for instance, when people escape a car accident with no serious injuries) are sometimes sufficient to cause an NDE, even if, in this case, the term isn't really appropriate.

The components of near-death experiences are highly spectacular. Indeed, it is characteristic to recall a feeling of intense well-being, of having the impression of leaving the body, seeing a bright light emerging from a tunnel-like dark spacel, losing the sense of time, visiting ‘another world’, being certain of having communicated with the dead or a mystical being, or a feeling of complete harmony with the universe. However, to be considered an ‘experiencer’ (someone who has had a near-death experience), it isn't necessary to have experienced all the characteristic phenomena of an NDE, just a certain number of them.

Neuroscientists and psychologists refer to specific scales to assess, as objectively as possible and in a standardised way, whether a subject has indeed had an NDE or not. The most commonly used one is the Greyson NDE scale. Exploring several aspects (cognitive, affective, paranormal, etc.), it is based on 16 questions with a score of 0, 1 or 2. A person can be said to have had an NDE if the total score obtained by an individual who answered the 16 questions is seven or more (out of 32).

Based on a cohort studied in 2014 (ref frontiers), the researchers found that the most reported feature is the feeling of well-being, followed by “out-of-body experiences” (OBE), seeing a brilliantbright light. In other words, NDE can have a variety of aspects. Vanessa Charland-Verville, an FNRS research fellow and a doctoral student in medical sciences in the University of Liège’s Coma Science Group and Liège CHU points out that NDE memories are most often interpreted through major cultural, philosophical and religious values.

Out-of-body experiences

The theories proposed to explain NDE can be grouped into three categories: spiritual, psychological and neurological.

Supporters of a spiritual explanation assert that these experiences prove the existence of a soul outside the body. They mainly support this theory based on the fact that one third of people who have had an out-of-body experience (OBE) state that they witnessed their resuscitation from above. During research carried out in Scandinavia, researchers decided to conceal images close to the ceiling of the operating theatre, that were invisible to a patient lying on the operating table. In 2008, a similar study was launched on an international level. It involved 25 hospitals. If the experiencers managed to confirm the presence of these hidden images on the ceiling, this would tend to prove that consciousness is probably separable from the body. For the time being, the issue has never been raised because no patient has ever reported seeing these images.

“The feeling that you're no longer in your body can occur in many circumstances, the moment certain brain connections are altered or even simply modified", Vanessa Charland-Verville points out. “Sometimes, extreme fatigue is enough.” The researcher adds that the brain 'likes’ to create meaning. It is also inclined to construct highly coherent stories underpinned by highly complex imagery, which the subject, cut off from the outside world, tends to interpret as emanating from it and having all the characteristics of reality.

Well, in that case, how do we explain experiencers who tell us, for instance, what was happening in the room next to where they were being resuscitated by the doctors? Vanessa Charland-Verville’s answer is that the information is always reported after the event and that we have no proof of what exactly went on in the adjacent room. In short, there is no scientific rigour involved. “There is a group of researchers in the field of NDE who seem to work in a circular manner", she says. “They believe in life after death and hence allow this belief to affect their conclusions. Of course, there are still many unanswered questions to be explored, but is this a reason for formulating assertions that aren’t based on any rigorous scientific observations? As far as I’m concerned, I would like to see the elaboration of experimental protocols: in science, you can only conclude on what you can test.”

Indeed, reports of isolated cases carry little weight in science.  Especially because statistical probability has to be taken into account. Furthermore, we can’t exclude the fact that some patients may have had flashes of consciousness during which they saw, heard or felt things. “Their memories could be comparable to those you might have when waking up from anaesthesia”, Vanessa Charland-Verville explains.

Dysfunction of regions of the brain

Let’s turn the page on the spiritual interpretations of NDE. Several psychological interpretations have also been put forward. According to one of them, these experiences consist of a form of depersonalisation, a feeling of losing your sense of reality, which acts as a means of defence when faced with the threat of death. It is as though our subconscious creates a ‘story’ to deny the imminence of our death. But in that case, how can we explain the occurrence of NDE when we aren't in a life-threatening situation? This interpretation is fragmentary at best.

The third category of explanatory theories is neurological. They certainly aren’t lacking but, for now, the most relevant ones associate the various components of NDE (tunnel of light, OBE, etc.) with a dysfunction of specific brain regions that have been injured, especially as a result of a head injury or a lack of oxygen caused by cardiac arrest. The facts plead in favour of this hypothesis. Let’s look at the example of out-of-body experiences again. In 2002, surgeons at the university hospital in Geneva involuntarily provoked an OBE in an epileptic patient by stimulating the right temporoparietal region of the brain. And five years later, a team from Antwerp experimentally obtained the same result by stimulating the same region through magnetic transcranial stimulation and implanted electrodes.

Flashbulb memories of hallucinations?

Regarding the chaotic conditions during which NDE are likely to take place, it is very difficult to study them in real time. Therefore, the researchers from ULg’s Coma Science Group and Liège CHU are aiming to connect the characteristics of NDEs reported by experiencers taking part in their studies, with possible residual lesions in brain regions likely to be responsible for the unusual experience these people have reported. We have just mentioned the right temporoparietal region for OBE, but there are other regions that could possibly ‘support’ other components of NDE.

During a cardiac arrest, a brain haemorrhage or a head injury, some regions of the brain suffer more than others, especially in response to a lack of oxygen.  These are the ones the researchers at ULg suspect of being involved in NDEs. “Even years after an NDE episode, the sensitivity of imaging techniques allows us to look for minuscule scars, the slightest epileptic activity, small oedemas or minor blood deposits that could suggest the presence of microlesions in a particular area of the brain”, Steven Laureys, head of the Coma Science Group, explained to us in 2013.

In association with ULg's Cognitive Psychology Unit, his team is also exploring the psychological aspect of NDE. Consequently, before using neuroimaging to test the neuroanatomical hypothesis – hence, to conduct systematic investigations aimed at better defining the neuronal correlates of the different components of NDE - the researchers are focusing on the phenomenological characteristics of memories of NDEs.

On 27 March 2013, the magazine PLos One published the results of the first study carried out by the team from Liège regarding the characteristics of NDE memories. The starting point was: are experiencers' accounts based on pure imaginary constructs or, on the contrary, do they have the attributes of memories of real events? It appeared that their wealth of sensorial, self-referential (relating to the subject themselves) and emotional details made the memories seem real. Their precision was such, according to Vanessa Charland-Verville, that experiencers refer to them as ‘hyper real’.  The researchers also established a bridge between these memories and flashbulb memories, which are very detailed entities firmly anchored in the memory, referring to circumstances during which we learnt of an important public event: the assassination of President Kennedy, the September 11 bombings, etc., - vivid circumstances with an intense emotional component that favour the encoding and mnesic trace of our actions.

“However, the characteristics of NDE memories don’t provide a basis for the reality of the events described (conversing with the dead, OBE, etc.), because physiological mechanisms could generate a perception that the experiencer believes relates to elements of external reality, whereas they are actually the fruit of a pure mental product”, Vanessa Charland-Verville adds.  Which led the team at ULg to suggest that NDE memories may be comparable with flashbulb memories of hallucinations.

The case of LIS patients

Nevertheless, psychologists and neuroscientists were certain that it would be a long time before they would be able to understand NDE memories on a phenomenological level. That’s why, in a study whose results were published in Frontiers in Human Neuroscience in 2014(1), they compared the items (content) and intensity of the NDE within various groups of patients who survived a coma as well as in subjects who had had an NDE even though their life wasn't in danger. No significant difference was noted between the groups of patients according to the cause of the coma (anoxia, trauma, other), or between these groups and the one where the members hadn't been faced with a real risk of near death. In March 2015, the researchers proceeded to focus on cases of patients with locked-in syndrome (LIS) in Consciousness and Cognition(2). These are patients who have suffered a coma and subsequently find themselves locked in a paralysed body while being fully conscious. In general, their only means of communication is blinking and vertical eye movements.

The great majority of experiencers are filled with positive emotions when they talk about their near-death experience. They allude to a moment of bliss and generally state that they become less materialistic, more altruistic, more turned towards spirituality, less afraid of death... But is it the same for LIS patients who’ve had an NDE? The question had never been asked and yet it deserved to be.

For several years, the Coma science Group has been working with the Association du locked-in syndrome (ALIS), in France. Vanessa Charland-Verville carried out the Greyson test on 40 LIS patients belonging to this association, as well as asking several extra questions such as, “Do you remember anything about your coma?” or “Did you have the feeling of dying?” “Fourteen LIS patients said they remembered the period around their coma and eight of them had scores on the Greyson scale allowing them to be considered as experiencers", the FNRS research fellow points out. The answers of these eight patients to the Greyson scale were compared to the answers of 23 non-LIS patients known to have had a classic NDE. The frequency of the phenomena they reported (OBE, tunnel of light, etc.) and the feelings experienced were relatively similar. However, the crucial point is that LIS patients reported having experienced significantly less positive feelings and emotions (well-being, peace, joy, harmony) than the ‘classic’ experiencers. Furthermore, the richness of their autobiographical memories (specifically, memories focused on the impression of having seen one’s life flash by in a fraction of a second) was much greater.

What's the reason behind these differences? According to the authors of the article in Consciousness and Cognition, there are two possible hypotheses. The first one is neuroanatomical. In LIS patients, the lesions are subtentorial, i.e. they are situated at the level of the cerebellum and the brainstem. On the other hand, in so-called ‘classic’ NDE, the lesions are supratentorial, i.e. located at the level of the encephalon(3). Could the location of the lesions explain why LIS patients have a less positive view of their NDE, which is filled with autobiographical details? It’s possible. “The brainstem has connections with the limbic system and the mesencephalon”, says Vanessa Charland-Verville. “Because of the influence on the amygdalae, which are known for their involvement in the emotion of fear, and on other structures in the limbic system, the alteration of these connections, which cause locked-in syndrome, could lead to feelings of panic or, at least, to far less well-being in the case of cortical lesions characteristic of classic NDE.”

The second hypothesis put forward to explain the differences observed between LIS patients who have experienced an NDE and other experiencers, relates to the context of emotional distress in which the former are plunged owing to the fact that their consciousness is intact in a paralysed body.  “It's difficult to draw a conclusion, but I think it's likely that both neuroanatomy and the context play a role and that therefore, the two hypotheses aren't mutually exclusive", the Coma Science Group researcher points out.

Lexical analysis

Continuing her exploration of NDE, Vanessa Charland-Verville is coordinating a project that follows on from the article published in 2013 in PLoS One. It involves the lexical analysis of NDE accounts using software. What words do experiencers most commonly use? And how are they associated? For instance, what are the chances that the word ‘light’ will be used in combination with the word ‘tunnel’? As a result, it should be possible to draw up a map of the correlations between the words. Ultimately, the goal is to determine how NDE accounts are organised and, in order to define their true meaning, to compare this organisation with those of accounts of dreams, striking events (flashbulb memories) or hallucinations caused by anaesthesia or ketamine administered to volunteers.

Moreover, Vanessa Charland-Verville offers a different outlook: “The lexical analysis must also allow us to establish a comparison between NDE accounts of different etiologies, bearing in mind that last year, we showed that the Greyson scale scores were very similar among near-death experiences caused by anoxia, a head injury or a haemorrhage. The same was true when an NDE (but, here, the term isn’t really appropriate) occurred in circumstances where the subject wasn’t in a life-threatening situation - syncope, meditation, sleep, anaesthesia, etc."

Nevertheless, we’re far from having completely untangled the phenomenological expression of near-death experiences. For the time being, the Coma Science Group researchers are using neuroimaging (fMRI, PET scans, EEG) to try to better define the cerebral correlates that may underpin – according to their hypothesis – the expression of the various components of NDE (OBE, tunnel of light, feeling of completeness, etc.). To bring the programme to a successful conclusion, they are particularly focusing on the brain function in volunteers who have had these odd experiences during a spontaneous and transitory loss of consciousness.

(1) Charland-Verville V, Jourdan JP, Thonnard M, Ledoux D, Donneau AF, Quertemont E, Laureys S. Near-death experiences in non-life-threatening events and coma of different etiologies. Frontiers in Human Neurosciences, 2014;8:203.
(2) Charland-Verville V, Lugo Z, Jourdan JP, Donneau AF, Laureys, S. Near-death experiences in patients with locked-in syndrome: not always a blissful journey. Consciousness and Cognition, 2015;34:28-32.

(3) The existence of subtentorial lesions in LIS patients doesn’t exclude the presence of other brain lesions that are potentially characteristic of components of NDE (OBE, tunnel of light, etc.) or damage affecting the connectivity of these regions. For their study, the Coma Science Group researchers didn’t have the MRI images for the patients concerned.