Biologist Bret Weinstein asks why fentanyl can leave people standing upright yet frozen in place...

"The answer is interesting.

It has to do with the fact that the way the drug takes out your consciousness, it leaves mechanisms—your proprioception is effectively left intact enough to keep you on your feet—resulting in what I think is technically called the fentanyl hang.

But the point is, this is so extreme that we don’t have the proper language for talking about it."
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https://www.youtube.com/watch?v=MI3OfCD6nj0