Brain Scans Probe the Limits of Consciousness

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By Nathaniel Scharping | May 27, 2016 4:03 pm
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(Credit: sfam_photo/Shutterstock)

New research from scientists at the University of Copenhagen and Yale University may offer a simple, yet powerful way to pull back the curtain on the true status of patients in a coma.

Using a type of Positron Emission Tomography (PET) scanning, the researchers say they were able to predict with 94 percent accuracy whether a coma patient would wake up. Typically, determining who will emerge from a coma is based on a doctor’s bedside exam, and they often make mistakes. They measured patients’ brain activity using a specialized camera that detected emissions from a radioactive glucose analogue that was introduced into their brains.

Glucose is what the brain gets its energy from — literally brain food — and by observing how much of the glucose was metabolized in the brain, the researchers were able to see how active the brain actually was.

Lighting the Brain Up

Researchers studied 131 patients in total, some of whom were in deep comas, as well as patients who displayed some basic responses to stimuli but were still considered to be comatose.

By tracking the patients for a year, they established a level of cerebral energy turnover necessary for a person to return to consciousness: 42 percent. The diagnosis was grim for patients whose brains were operating beneath that threshold, most either died or remained in a coma — although one patient did progress to a slightly more responsive state. The prospects were much brighter for those who were totally unresponsive but had higher levels of brain activity: of 11 patients, eight recovered. They say that 42 percent of normal cortical activity represents a baseline for our brains — any lower and we just can’t heal ourselves.

The test could offer hope to those with family members in a coma, as well as give doctors a prognosis and help to establish a rough timeframe for recovery. In addition, it provides valuable insights on the question looming over every coma patient: when to pull the plug and allow them to die. The researchers published their work Thursday in the journal Current Biology.

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Images from PET scans comparing fully conscious control subjects to coma patients. (Credit: Stender et. al)

Strong Link Between Energy Use and Consciousness

While the team acknowledged that they have not provided a definite causal link between glucose metabolism and brain activity, they say that their data strongly indicates such a relationship.

Researchers say they reliably modeled a patient’s level of consciousness based on their brain’s energy consumption. They also looked at the differences between patients who had some level of response to verbal or visual clues, and found that the corresponding brain regions displayed greater signs of metabolism when compared to other parts of the brain, providing further evidence of the link between energy use and level of consciousness.

In addition to applications for coma patients, this research offers insight into fundamental questions about human consciousness. Identifying a metabolic threshold for recovering consciousness in humans narrows down the search for the basic prerequisites of life in humans. In the future, the researchers hope to extend their observations of coma patients beyond a year, as many people remain in comas for much longer. They also hope to expand the sample size of their study and have their work replicated by other researchers.

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  • ld_elon

    Problem with the brain dead, is the fact their having an out of body experience, although You could stimulate the brain with a ‘usual brain pattern’ material

    garment platform hardware interface, {a thin rounded hat with heat and

    vibrational sensor pads} enabling the retuning of the normal brain

    display an at correct temperatures, its unlikely their actually present around their own bodies, its easy to follow the light in death, regardless of which sinner holds it..

    • ld_elon

      Have to remove the hair, hair cause distortions.

      • ld_elon

        You also need to focus more on the lower center back of the head.

  • M Peirce

    Perhaps I’m missing something here (I’ve not looked at the cited paper yet), but level of neural activity is, well…, just that. It seems to be a mistake to assume further, that it correlates with “level of consciousness” unless we are stipulating, as an operational definition, that that’s what consciousness is. But in that case, we avoid hard questions about the nature of consciousness, and the reported conclusion follows by definition, instead of shedding light on the interrelation between levels of neural activity and consciousness.

    Moreover, based on patient reports, when people are in a coma, they are not conscious, not at least in the very important sense of there being something it is like to be in such a state. There is something it is like to be dreaming, but not something it is like to be in a non-dreaming sleep state, nor to be knocked out, nor to be in an alcohol induced blackout (although this last may be more a matter of not remembering than not being conscious at the time). If I’m not misinterpreting a lot of data, the level of neural activity in dreamless sleep is still quite high, making the level of neural activity a poor correlate for consciousness in this sense of the term.

    So, count me as baffled about the claim that this provides “evidence of the link between energy use and level of consciousness.” The relevant dots do not seem to have been connected.

    • sjl4evr

      I also have not read the paper yet, but this article states only “neural activity” and nothing about exactly where the neural activity was occurring. If there is no, or minor activity in the prefrontal cortex, then really, what good is it to have activity somewhere else in the brain? Also, I am personally an exception to the rule of requiring the brain to demonstrate a certain level of activity to determine prognosis. After a bad wreck, I suffered cardiac arrest 4 separate times, and required drugs and defib to “come back”. I don’t know exactly how long I was “out” in total, but it was at least more than the “magic” 6 minutes, as my family was told to expect that I would have severe brain damage and probably never go past a persistent vegetative state. Obviously, they were wrong.

    • MoonStroller

      Something consuming energy could be construed as being animated, perhaps more than alive, considering it’s the human brain being considered.

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