The question is a bit weird, so I’ll clarify.
To my knowledge, the brain is part of the nervous system, which is what lets you feel things. If the brain was severed from the rest of the system (Like at the base of the skull) would you feel pain there or would you just feel nothing?
In: Biology
Yes. That’s basically phantom pain syndrome. Phantom pain syndrome is caused by your thalamus (the part of your brain that sends and receives the signals coming from or going to the parts of your body that aren’t the brain) not really knowing how to deal with there being absolute radio silence from a limb or part of a limb, so it concludes “hey, leg 2 isn’t responding, ummmm, I’m gonna pass that onto the parietal lobe (the part of your brain responsible for interpreting physical sensations like touch and and is one of the parts that has the authority to hit the ‘pain’ button) and the parietal lobe goes “hmm, the thalamus is reporting radio silence from leg 2, I don’t know how to deal with this, so I’m just gonna assume something is wrong and hit the pain button, just in case”.
So, ya feel pain. It’s also why people with amputated limbs report still feeling the injury they had which caused the amputation, parietal lobe hasn’t been told anything new so it just assumes it’s still the same story and hits the pain button. It sometimes fades, sometimes doesn’t.
As for phantom limb syndrome, which would also be the case, well, that’s a completely different story. We have more than 5 senses, and one of the other ones is something called kinesthesis. Kinesthesis is essentially how you can close your eyes or look at something that isn’t your body and know where your limbs and body are and what position you’re in. What we call ‘muscle memory’ is essentially Kinesthetic Intelligence. You get better at knowing what movements to make and how to make them. The parts of your brain that are responsible for kinesthesis are the Posterior Parietal cortex as well as of the Primary Motor cortex, and if you’ve ever tried to learn how to play an instrument, you know those parts take a lot of effort to train. Same story for losing a limb or becoming paraplegic or quadriplegic (which is the scenario you describe), it’s pretty friggin hard to unlearn that you have an arm, or rather learn that you don’t have an arm, especially if you have a fake arm which acts like an arm, which satisfies those cortexes enough to keep the ‘dream’ of you having an arm alive.
That’s also why tools and machinery feel like extensions of our body and can be operated without thinking about the literal motions or actions you’re making to manipulate the tool to do the thing, instead you just think about what you want the tool or machinery to do and your actions make it happen, the Posterior Parietal cortex and the Primary Motor cortex, your Kinesthetic Intelligence, takes over and accepts the tool or machinery as an extension of your body in the same way it controls your hand, you don’t think about the muscle movements required to touch your nose with your finger, you just do it thanks to those cortexes dealing with that stuff automatically.
And let’s not even get started on your reflexes, that isn’t even in your brain, that’s actually in your spinal cord and brain stem and is even more primitive than those cortexes.
So yeah. If you were made quadriplegic, or you had ALS (what Stephen Hawking had), the part of your brain responsible for pain, physical sensations, Kinesthesis and motor control would still work, and initially they’d be super confused, but eventually they’d adapt to it.
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