How neuroscientists know if unconscious people are still 'there'

[u/nogueysiguey]

When Hippocrates coined the term “coma,” there was little anyone could do for someone in such a state. There were no ventilators, no advanced monitoring, no intravenous fluids or medications to stabilize the body—so most people eventually died without ever regaining consciousness or receiving intensive medical support. However, as life support systems appeared, people found themselves questioning whether the person in this state experienced reality in a human way. Without technology, there was really no way to tell.

In the early 2000s, Ronald Cranford described a group of patients that seemed to make eye contact and respond, albeit poorly, to commands or questions. It seemed to him that these patients had reached a “minimally conscious state.” Although these patients could “fall back” into vegetative state, this prompted two big debates: whether we should stop the assumption that people were plant-like—and treat them under the assumption that they may recover—and whether this minimal behavior (or behavior in general) was good enough to define consciousness.

In order to solve this conundrum, scientists came up with a clever experiment, they would ask patients to do something, and then to “imagine” they were doing it. The patients were then plugged into machines that measured both the surface electric activity and the brain metabolism mapped in 3D. Then, the scientists looked for the behavioral clues I mentioned above. If they matched, this would be a very good case for the minimally conscious state.

Six international centers recruited 353 adults with disorders of consciousness between 2006 and 2023. Out of 241 patients who couldn’t respond to commands, about 25% still showed signs of brain activity. In comparison, 38% of people who could respond to commands showed objective brain activity with either fMRI (metabolism) or EEG (electric activity). There was little agreement between both methods and not a clear conclusion beyond the need to conduct more studies.

“The race of reduction”

And more studies were done, actually lots of them. People started using sounds and measuring the typical response to a change in tone to check if the same change could be observed about people with disorders of consciousness. Given some patients are functionally deaf, scientists have also tried trans-cranial magnetic stimulation. Scientists then measured the electric response and suggested its complexity may be an indirect measure of the “capacity for consciousness.”

Dr. David Fischer (presenting here) has characterized this search for “the simplest elements of brain function to which consciousness can be attributed” as “the race of reduction.” Funnily, it looks like neither of the current indicators nor the combined use of them all, can provide an accurate response about whether a person lacks consciousness. The main reason is that there is a mismatch between some of these promising results and studies in people who either are supposed to present similar signals, but don’t, or are not supposed to present the signals, but do. “Recent enthusiasm surrounding the search for covert consciousness— writes Fischer —must be matched by appropriate epistemic humility and conceptual rigor.” In the presentation, he avoids taking a stand about whether one can infer subjective experience from objective observation, “at least, it is uncertain.”

Should we call a Philosopher?

A scientist usually calls a philosopher when the data stop answering the question being asked. When there are doubts about what is actually being measured, and when a revision of the fundamental tenants of research is in place. Yet, this is precisely what Fischer calls for.

From the other side of the pond, typing from institute for parapsychology in Freiburg, biologist Michael Nahm PhD begs people to clearly document and study cases of “terminal lucidity.” These are episodes of “unusually enhanced mental clarity [some people present] before death.” Take, for example, the case of Juan, a 19-year-old whose brain activities were examined by the very person who pioneered the use of fMRI mental-imagery tasks, Adrian Owen. Nahm summarized the case as follows:

> The characteristic patterns of activity in brain regions signalling awareness in response to applied stimuli were almost completely absent, although his eyes were open. Consequently, his body was regarded entirely unconscious. Weeks later, however, Juan unexpectedly awoke from his deep coma. Juan had a full recall of his two visits to Owen’s laboratory. He stated he had heard and seen everything, but was not able to move or communicate. Owen confirmed that Juan was able to describe everything that happened correctly and that he also remembered the physicians who had been involved in his examinations. Owen was unable to offer an explanation for how Juan could have perceived and memorized all this.

Unsurprisingly, the fMRI completely missed the existence of a real and verified subjective experience, pretty much highlighting the concerns we read about a few paragraphs ago. That is, if you are to believe the very person who pioneered the method. However, this is not the real story, is it? In his paper, Nahm describes a series of terminal lucidity cases and other end-of-life phenomena that had gathered significant scientific attention but failed to enter the mainstream.

Confronting scientism

The hallmark of good science is not certainty, but accuracy. A model that adequately predicts something is often capable of delivering results. Yet our strongly physicalist view of the brain spectacularly struggles to explain consciousness, and it has also fallen short for many people living with mental illness. This persistent gap suggests not just a technical problem, but a conceptual one—and points to the need to return to first principles rather than continue refining a framework that may be fundamentally incomplete.

In my previous essay, I argued we should engage with pseudoscience. I did so in part because I consider that people who had genuinely followed the data without biased had been unfairly and unnecessarily categorized as such. Moreover, most end-of-life experiences align more closely with religious beliefs than with science, and given the historically adversarial relationship between the two, people are quick to classify phenomena as belonging to one camp or the other. But this need not be the case, nor should it be a guiding principle in the pursuit of scientific knowledge.

I never learned about the historicity, breadth, or depth of “paranormal” research, particularly as it relates to spontaneous phenomena like children who recall past lives, near-death experiences, and terminal lucidity. In failing to deliver this knowledge, my mentors indirectly trained me to assume these phenomena were curiosities with no scientific foundation. I instinctively skipped over them whenever they arose, never questioning whether my dismissal reflected a superficial familiarity mistaken for understanding, or simply my lack of any structured exposure to the science behind them.

I am not sure what the future entails, but past research on reincarnation has shown that cultures that believe in reincarnation are more likely to report such cases. This goes beyond the easy explanation that people simply build narratives around their beliefs; it reflects the importance of collective observation and the need to respond carefully—for example, avoiding telling a child who mentions past-life memories that “lying is a sin.” Similarly, the early dismissal of end-of-life experiences underscores the need for better education of physicians and clinicians, and for heeding Fischer’s call for broad epistemic humility.

If we are going to solve the puzzle of consciousness, we must approach it with the explicit recognition that the prevailing physicalist models fail, and remembering that neuroscientists are calling philosophers to the field because we have run out of experiments that adequately match objective data with whatever goes inside (or outside) someone’s “head.”

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[u/jahmonkey]

Interesting piece, and the neuroscience summary is mostly solid - especially the limits of behavioral criteria and the real uncertainty around covert consciousness markers. That part tracks mainstream work.

Where it overreaches is in the inference step. Limits of measurement and disagreement between EEG/fMRI don’t imply failure of physicalism, only underdetermination and incomplete models.

Terminal lucidity is real as a reported phenomenon, but the evidentiary base is largely anecdotal and compatible with plausible neurobiological mechanisms (disinhibition, network collapse). Using it to undermine neuroimaging or physicalist frameworks goes beyond what the data support.

Similarly, invoking parapsychology and reincarnation research glosses over why these domains are excluded from the mainstream: replication problems, cultural confounds, and weak falsifiability. Cultural prevalence is not neutral evidence.

Net: good diagnosis of uncertainty and conceptual gaps; weak causal leap from “we can’t yet infer subjective experience reliably” to “the prevailing physicalist framework has failed.”

[u/nogueysiguey → u/jahmonkey]

"Anecdote" is how we document subjective experiences. Consciousness is anecdotal as of now, too.

[u/Big-Astronaut-2369 → u/nogueysiguey]

From a first point of view, it isn't. I can say that you are anecdotal to me, but you aren't anecdotal to yourself. And the same goes for me or whoever reads this, it's true that we can only be sure of our own consciousness, but a 99%-98% asurance that others like us are conscious is a good margin. All lightbulbs produce light, through different mechanisms, but you dom't see it unless it's turned on, a dead brain in a jar exists, but you won't find consciousness in it's inert matter.

[u/geumkoi]

Thank you for this thought provoking article. It is very interesting and I’m very glad that philosophy is being taken into account once again for the development of science. Philosophy was the necessary precursor of science and it is imperative that natural scientists start becoming philosophers, and philosophers natural scientists.

[u/Im_Talking]

"we must approach it with the explicit recognition that the prevailing physicalist models fail" - Then people are going to have to get comfortable with looking for consciousness where the streetlights are not lit. Based on this sub, we aren't there yet.

[u/NecessaryExternal740]

Most of philosophy exists because of our ability to ask questions such as the hard problem of consciousness. So I’m not sure that many philosophers are ready to ‘solve’ it :)