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by Defenestresque 1094 days ago

I was skeptical of the article's claims that anesthetized patients may continue to experience consciousness, but this has definitely shaken the foundations of that belief:

>At doses near the unconsciousness threshold, some anesthetics block working memory (20). Thus, patients may fail to respond because they immediately forget what to do. At much lower doses, anesthetics cause profound amnesia. Studies with the isolated forearm technique, in which a tourniquet is applied to the arm before paralysis is induced (to allow the hand to move while the rest of the body is paralyzed), show that patients under general anesthesia can sometimes carry on a conversation using hand signals, but post-operatively deny ever being awake (21). Thus, retrospective oblivion is no proof of unconsciousness.

Edit: there are some sections of this article that could prompt some interesting discussion from the crowd here. For example, from a subsection "Consciousness and integrated information":

>The evidence from anesthesia and sleep states (Fig. 2–3) converges to suggest that loss of consciousness is associated with a breakdown of cortical connectivity and thus of integration, or with a collapse of the repertoire of cortical activity patterns and thus of information (Fig. 2). Why should this be the case? A recent theory suggests a principled reason: information and integration may be the very essence of consciousness (52). Classically, information is the reduction of uncertainty among alternatives: when a coin falls on one of its two sides, it provides 1 bit of information, whereas a die falling on one of six faces provides ~2.6 bits. But then having any conscious experience, even one of pure darkness, must be extraordinarily informative, since we could have had countless other experiences instead (think of all the frames of every possible movie). Having any experience is like throwing a die with a trillion faces and identifying which number came up (Fig. 2). On the other hand, every experience is an integrated whole that cannot be subdivided into independent components. For example, with an intact brain you cannot experience the left half of the visual field independently of the right half, or visual shapes independently of their color. In other words, the die of experience is a single one throwing multiple dice and combining the numbers will not do.

5 comments

jillesvangurp 1094 days ago

Many years ago, I received a mild sedative while undergoing an endoscopy via my throat. Apparently, that's not a pleasant experience. I say apparently because I have no memory of it other than asking the nurse when they were going to start ... after the procedure was completed. I remember getting injected with the stuff and I remember me asking that question because I was getting bored just lying there. I don't remember losing consciousness, being asleep, or waking up, or anything like that. It's just a gap in my memory while they did their thing. Amazing stuff. I'm assuming I was conscious and responsive throughout.

I had proper surgery a few days later which involved being knocked out for two hours or so. That's a whole different situation. You start counting down and you are gone within a few seconds.