A few days ago I had to get surgery on my knee. Long story short, it's a jiu-jistu injury, the initial tear (probably) happened about 6 months ago because I didn't tap when I should have. Part of the surgical procedure involved putting me under general anaesthesia so the orthopedic surgeon could make a few incisions around my knee and cut out part of my meniscus. I walked away from that experience far more fascinated about what happened to "me" under anaesthesia than what the surgeon had done to my knee.
Coincidentally, just a few days after surgery, I started reading Being You: A New Science Science of Consciousness by Anil Seth, where he begins the prologue describing his experience of anaesthesia — "I had ceased to exist". He says that "by altering the delicate electrochemical balance within the neural circuitry inside your head, the basic ground state of what it is to 'be' is —temporarily— abolished."
Anaesthesia is different than simply falling asleep or passing out. When you're asleep, you're still conscious to an extent otherwise you wouldn't wake up to someone banging on a drum or splashing cold water in your face. One moment I was seeing the doctor and nurses preparing for surgery and strapping me into a table. The anaesthesiologist saying he's giving me some "liquid courage" via my IV, and put an oxygen mask over my face saying "Just take a deep breath.... and another deep breath". I was lying there thinking "I wonder how this is going to work", paying attention my breathing and seeing if I noticed any changes to my perception, then the next moment I was in another room, where more than an hour had passed.
I had experienced no time whatsoever, as though I had time traveled one hour into the future, albeit feeling a bit groggy. I've perceived distortions in my subjective experience of time due to experimenting with psychoactive substances in my younger years, and I've also experienced alcohol "black outs" where I was conscious during a period, but had no memory of the evening the following day day (though according to my friends told, I acted a fool).
Under anaesthesia, I had no time perception, no sense perception, no consciousness whatsoever. It was a complete absence of everything and probably the closest thing I've ever come to death.
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