National Geographic

Consciousness is a Process

Last week my fellow Phenom Ed Yong wrote a post about what happens to consciousness when animals die. According to the research Ed described, a rat’s brain shows signs of consciousness for at least 30 seconds after its heart stops.

That study got a lot of buzz, understandably, because of what it implies about near-death experiences: namely, that they’re more likely the product of a human mind than of some mystical power.

But Ed’s post also raised some more nuanced — and I think, more profound — questions about the work. For example, coma expert Steven Laureys of the University of Liège pointed out that nobody really knows yet how to determine whether an animal is conscious or unconscious by looking at its brain waves alone. “It’s terribly hard to make strong claims about what these rats actually perceived, or about possible conscious experiences,” Laureys told Ed.

But that line of research is advancing rapidly. Just two days after the rat study came out, researchers in Italy reported a new method for decoding neural signals of consciousness — in people. Marcello Massimini’s team from the University of Milan found that people in different states of consciousness will respond to a non-invasive electromagnetic pulse with distinctive patterns of brain waves.

If other groups confirm that these waves are reliable markers of consciousness, it would be a huge help to doctors who treat people with brain injuries. Many of these patients look the same from the outside — they don’t respond to doctors or loved ones with words, say, or eye blinks, or hand squeezes. But they are not the same. Some 68 percent will recover consciousness within a year, and 21 percent will lead independent lives, according to one study. What’s more, some people gain consciousness one, two or even five years after their injury.

With current technologies, however, it’s extremely difficult for doctors to predict which patients will have positive outcomes and which will never break through. In 2009, Laureys’s group estimated that 41 percent of people diagnosed as being in a vegetative state (a murky state of biological arousal without any conscious awareness) were later found to have some level of consciousness.

Massimini’s solution relies on a technology called transcranial magnetic stimulation, or TMS, in which researchers place a wand on the person’s head. The wand contains a magnetic coil, which produces an electromagnetic pulse that passes through the person’s skull and tickles the neurons underneath. The neurons respond to that pulse, and the researchers then measure that neuronal response via EEG electrodes places all over the scalp.

The researchers created algorithms that analyze the patterns of EEG response and spit out a number — the “perturbational complexity index”, or PCI — between 0 and 1. PCI is based on the idea that consciousness arises when groups of neurons show responses that are both unique and coordinated. As Nicholas Schiff, a neuroscientist at Cornell University, explained it in a related commentary: “High PCI values are obtained only if the initial TMS perturbation alters activity in a large set of integrated brain regions that each then react differently over time.”

It’s complicated stuff. This video, created by the researchers, describes the technique visually, which helped me understand it:


Video by Adenauer G. Casali

Once they had refined their methods for calculating PCI, the researchers tested its validity on 32 healthy people while they were either: awake, in dreaming sleep, in deep (unconscious) sleep, or under various kinds of anesthesia. The lowest PCI recorded during a conscious state was .44, and the highest PCI recorded in an unconscious state was .31, suggesting that consciousness emerges somewhere, somehow, in between.

The team then showed that PCI could also accurately identify consciousness in 20 people with brain injuries. Six people in a vegetative state, for example, had PCI scores between .19 and .31 — in the same range as healthy people who were in deep sleep or drugged. In contrast, two patients with locked-in syndrome — a condition in which people are aware and have normal thinking abilities, but cannot communicate because of total body paralysis — had PCI scores ranging from .51 to .62, no different from awake healthy people.

There’s still much to be done before this new technology can be tested in the clinic. The sample size was pretty small. And it’s not clear yet whether PCI can reliable distinguish between patients who have a minimum level of consciousness and those who have none — the distinction that’s arguably the most difficult and important in a clinical setting.

I like the study, though, because it emphasizes an essential point that also came out of the rat study.

“Doctors assume that after clinical death, the brain is dead and inactive,” the rat study’s lead investigator, Jimo Borjigin, told Ed. “They use the term ‘unconscious’ again and again. But death is a process. It’s not a black-or-white line.”

Right, death is a process. But consciousness, too, is a process — a very slippery one.

There are 13 Comments. Add Yours.

  1. John Kubie
    August 20, 2013

    “consciousness is a process”. Like a car engine, it’s either running or not. Looking at a still engine before startup gives little indication of whether it will or can run. Like a car engine, once started it can continue on its own.

  2. Kathy K.
    August 20, 2013

    Thanks for this excellent article. That video is also excellent.
    I’d like to know where night terrors/wakeful dreaming falls in this range of consciousness?
    Anybody who has ever witnessed these in children can tell you how frustrating they can be. I could never find a good explanation for them.

  3. cristian andrei
    August 23, 2013

    Consciousness is not a car engine. It is like the spring on earth. In some places (in regard with some things) is flourishing, in others does not seem to exist.

  4. Mfa
    August 23, 2013

    Even when youre rest, another part of your brain is still working. So its not car engine that could be “run or stop”!

    • John Kubie
      August 23, 2013

      “even when you rest …” clearly, the car engine metaphor is simplifying. but the attentive state is self-generative. A clear example of the ‘car engine’ metaphor are from patients in vegetative states who can be made ‘conscious’ via deep-brain stim in an area of cortex that is healthy, but quiescent. In my mind, saying ‘consciousness is a process’ is equivalent to saying it is a ‘state’. The implication is that a region of cortex can be in a variety of states, some of which produce ‘consciousness’.

  5. Lt Col H B Mukherjee ( Retd)
    August 25, 2013

    Its amazing to learn the depth of research the scientists are conducting for the benefit of mankind. Hats off to them.

  6. Eccemarco
    August 27, 2013

    Dear Virginia,
    Thanks for your article. I wonder if you have matched these findings with what prof John Searle says about consciousness. He basically posits exactly the same, that consciousness is a process -like digestion. Its physiological basis resides in the brain, and yet it cannot be reduced to any simple sub-process from which it originates.

  7. Max_B
    September 1, 2013

    Hmmm… That video indicates the researchers PCI theory classified Non-Rapid-Eye-Movement (NREM) Sleep as ‘Unconsciousness’, rather than a different state of consciousness? Yet, we know that perfectly healthy people dream during NREM sleep… it’s just found to be less common than dreaming during REM sleep.

    Concentrating ‘purely’ on Neurons, really doesn’t fit very well with our observations and subjective evidence of recalled experiences during states of reduced blood flow in the brain etc.

    Highly syncronised neuronal activity seems to correlate better with ‘focused’ conscious awareness. So, perhaps it’s better to think of neuron firing as acting like an incredibly narrow ‘focusing lens’, controlling input to some other deeper, and far more powerful process that presently lies beyond our ability to investigate.

  8. Max_B
    September 1, 2013

    Hmmm… That video indicates the researchers PCI theory classified Non-Rapid-Eye-Movement (NREM) Sleep as ‘Unconsciousness’, rather than a different state of consciousness? Yet, we know that perfectly healthy people dream during NREM sleep… it’s just found to be less common than dreaming during REM sleep.

    Concentrating ‘purely’ on Neurons, really doesn’t fit very well with our observations and subjective evidence of recalled experiences during states of reduced blood flow in the brain etc.

    Highly synchronised neuronal activity seems to correlate better with ‘focused’ conscious awareness. So, perhaps it’s better to think of neuron firing as acting like an incredibly narrow ‘focusing lens’, controlling input to some other deeper, and far more powerful process that presently lies beyond our ability to investigate.

  9. M R Shetty
    September 1, 2013

    “Consciousness is the globalization of
    the electrical and chemical activity within the brain”
    M R Shetty

  10. Ralph Dratman
    September 22, 2013

    The ability to determine whether a person is definitely unconscious would also be of great value to anesthesiologists, who surprisingly still cannot be 100% certain their patient is completely “out.” A small minority of patients later report having been conscious for part or all of a surgical procedure, though unable to move. Some of those patients can accurately remember details about what was going on around them during the surgery, such as what the surgeon and others present were talking about.

    Naturally enough, anesthesiologists would prefer to know for certain, at all times, that a patient in surgery is experiencing nothing whatsoever. Likewise it would be helpful to know when consciousness of some level has returned.

  11. Lucid Dreamer Nightly
    September 30, 2013

    I Lucid Dream nightly. I recall some or most of the details 70% of the time. Upon waking some mornings I truly need to gather myself as the dream was so clear I was feeling as if I was still living the dream.. anyone else?

  12. m r shetty
    November 29, 2013

    consciousness obliterates the dream
    because the dream is stored short term memory
    m r shetty

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