Oh I agree – once it’s fed.
Your brain gets fed through your nervous system from the very first set of nerve cells in the womb.
By the time we’re able to use language, comprehending nearly the entire grammatical system of our native language and enough vocabulary to have what we’d consider ”adult conversations’; that is, ‘reasonable’…
…we’re 3.5 to 4 yrs old.
We learn a lot from that point on, but most of it is social and ‘facts’; but we’ve already experienced dreams, emotions, curiosity, wonder, beliefs, hopes, logic…
and if a disability befell us at that point in time, even the rest of our inputs shut down for some awful reason… our brains would have more than enough to continue with on their own at some level.
Of course that’s extreme. But think about it: That’s why we can strap 5-6 yr old kids in desks where they can’t move. They don’t ‘need’ their bodies as much to feed their brains anymore.
But you can’t do that to babies. They die if they don’t get coddled, sweet-talked, touched. We’re social creatures and input is required from the beginning for us to survive. After a while we can manage without it as much but at the start? The brain doesn’t act alone without input. It can’t. Input is required initially for human life to continue.