Disconnecting Consciousness from the External Environment

By Neuroskeptic | February 23, 2014 12:08 pm

An very interesting report from a group of French neurosurgeons sheds light on the neural basis of consciousness and dreams.

Guillaume Herbet and colleagues describe the case of a 45 year old man in whom electrical stimulation of a particular spot in the brain “induced a dramatic alteration of conscious experience in a highly reproducible manner.”

The man had brain cancer (a diffuse low-grade glioma of the posterior left hemisphere). During the surgery to remove the tumour, Herbet et al stimulated various points on his brain to map out the areas that were functionally most important. This is a standard procedure to allow surgeons to know which bits they ought to leave intact, where possible.

Most of the stimulations didn’t do much, but there was a particular point, in the white matter beneath the left posterior cingulate cortex (PCC), where the electrical pulse caused the patient to become unresponsive – to ‘zone out’, essentially – for a few seconds. This point is marked as “S1” (small blue spot) on these images. The red zone on the left is the area that was eventually removed.

consciousness_herbetUpon regaining awareness after the stimulation, the patient reported that he had been ‘in a dream’. Three stimulations of the same area produced three such reveries:

Quite surprisingly, he described himself retrospectively as in a dream, outside the operating room, and was able to fleetingly report his subjective experiences (stimulation 1: “I was as in a dream, there was a sun”; stimulation 2: I was as in a dream, I was on the beach”; stimulation 3: “I was as in a dream, I was surrounded by a white landscape”. No additional sites in the surrounding anatomical space were found to elicit this manifestation.

Suns and beaches doesn’t sound like the stuff of nightmares. But the patient said that these dreams were, in fact, unspeakably horrible:

However, the simple mention of the event was associated with a strong emotional discharge, including crying and tremors, and finally the patient always said: “I don’t remember, I don’t want to remember”

All very gothic. But what does it mean? Herbet et al say that

Disrupting the subcortical connectivity of the left posterior cingulate cortex (PCC) reliably induced a breakdown in conscious experience.

Which fits with the theory that the PCC – a ringleader of the brain’s default mode network – is central to waking consciousness. But what’s odd is that a large chunk of the left PCC was not just disrupted but permanently cut out, and it didn’t destroy the patient’s consciousness – although

He reported experiencing no rumination and no negative thought for almost a month after the surgery. He described himself in a kind of contemplative state, with a subjective feeling of absolute happiness and timelessness.

Sounds almost like spiritual enlightenment, but it only lasted a month; after that, it seems, he returned more or less to normal consciousness – even thought that chunk of PCC was still gone. So I’d say this case report, while fascinating, raises more questions than it answers.

ResearchBlogging.orgHerbet G, Lafargue G, de Champfleur NM, Moritz-Gasser S, le Bars E, Bonnetblanc F, & Duffau H (2014). Disrupting posterior cingulate connectivity disconnects consciousness from the external environment. Neuropsychologia, 56C, 239-244 PMID: 24508051

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  • Alex D.

    Really interesting.

    • EverSubtle

      Yes, really interesting, and really scarey.

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  • http://www.amazon.com/Rolf-Degen/e/B001K1NBP4/ref=ntt_athr_dp_pel_2 Rolf Degen

    Just doing a quick search shows that the left posterior cingulate cortex seems to be an jack-of-all-trades structure in the brain: Its activity is enhanced during autobiographical recollection, when telling lies, when hearing music and when being in love for a short time.

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  • Bill Skaggs

    I don’t have access to this paper, but the “zoning out” suggests to me that the stimulation might have been causing a petit mal seizure. If that’s the case, then there would have been a spread of activity, and all bets are off as to what it means. Did the authors report anything that rules this out?

    Regards, Bill

    • http://blogs.discovermagazine.com/neuroskeptic/ Neuroskeptic

      Interesting idea! I don’t think they were able to rule that out.

      • http://blogs.discovermagazine.com Samuel Lieblich

        I have read the paper. They used the 60hz direct stimulation technique which has elsewhere been associated with seizures in 9.5% of cases (http://www.ncbi.nlm.nih.gov/pubmed/17277576). They do not report on EEG remote to the site of stimulation… would be a good question for the authors.

      • teknowh0re

        I tend to agree. 5 years ago, due to being on tramadol, I experienced 6 bouts of what they call “seratonin syndrome”, and as a result I had 6 very bad grand mal seizures. Strangely, I experienced a VERY similar thing! Each time it was different. The first time, it was like I was traveling, floating, through a tunnel but backwards, and I heard this…indescribably creepy music and voices. When I came out of it, I thought (and felt for a long time after) that I had actually died. The next few, I was bathed in very bright light, it was very strange as if I was vaguely conscious, but through a very thick fog. The weird thing though, was that all of those first 5 episodes REALLY freaked me out. Recalling them, talking about them, really made me extremely emotional in a way that terrified me for some reason. And I can’t help but think that the reason for that, and for this mans terror, must be due to the fact that we were not on our normal conscious plane, but somewhere else. And this scared us on a deep, instinctual level.
        When I first read this article, I thought his experience sounded like maybe he was dying when this brain area was stimulated. But I agree with you that perhaps it was a seizure indeed.

  • templeruins

    As the PCC is linked (along with many other functions) with dissociative states, that month of ecstasy he experienced seems interesting. You mentioned a state of enlightenment, which is interesting also in regard to tradtitional routes to Nirvana include a a shift away from sensory stimuli and memory and historical (mind) factors related to the function of the PCC to ‘calm’ the mind, and then entering (in one way) an “ecstatic trance” (samadhi), followed by Nirvana (very crudely put).

    Also to be surely noted here, is that the PCC has been clinically studied during meditation, and has been found to be ‘deactivated’ during meditation (see http://www.ncbi.nlm.nih.gov/pubmed/23964222

    Food for thought.

  • http://blogs.discovermagazine.com Longmire

    I took a trip to the future and was given the opportunity to bathe my soul in the orb of collective experiences. As the experiences flowed thru my mind I could see them projected before me, choosing to entertain them or letting them dissolve, I could even freeze them and banish them from returning or require them to return in a given sequence. This was a right of passage there, where one chooses the routine of there consciousness. Come to find out the only real important thing is awareness which gives birth to the experience, which is good, while the lack of it is what causes suffering. It all fundamentally has to do with the nature of things which Einstein poked at with his E=mc2 which means energy parallels matter diverging freely but the concept not grasped as of yet is energy parallels matter at all levels. That is why the mans consciousness returned to “normal” while the matter was removed the energy was not and it regrew the brain as it could to arrive at his static awareness. We can not simply remove the pcc to gain enlightenment but they have figured out how to create a closed loop of it to allow its energy and matter to remain, yet have no influence on the psyche. Oh yeah what we call enlightenment they call a basic right.

  • Utica

    He was left with motor skills, memory, and the ability to form new memories. So no frustration, depression, or anxiety. Just glad to be alive, and on the mend. My bet is rebirth or second infancy experience… babies feel stress on the body… hunger, wet, cold, hot, pain, etc. when these are relieved they feel comfortable, and relaxed. He lost a chunk of his brain. Which is quickly trying to catch up by creating new connections. Stroke patients commonly exhibit a variety of emotional states as they mend or adjust…

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Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.


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