ELI5: What does exactly happen in your brain when you try to remember something but cannot and then you remember it out of nowhere after a while

I think it's definitely possible to create a mind of some kind. But a human mind? No freaking way. Why not? Complexity. In general, people really have no idea how complicated the brain is. It's more complicated than you think, no matter how complicated you think it is. :)

People think of the human brain like a computer program or network, which makes sense given (1) our limited understanding, and (2) our limited frame of reference. Neurons have inputs, and if enough of them happen at the same time, the neuron fires. We can write a program to describe that... right?

In reality, signals travel in both directions, sometimes in loops with varying numbers of neurons involved--computer networks cannot do this (see Spanning Tree Protocol)--using dozens of different neurotransmitters affecting hundreds of receptors, most of which are made of more than one protein, which can be mixed and matched, AND most of these proteins have multiple isoforms, which get swapped out in order to slightly alter the characteristics of one receptor.

The brain does not produce new neurons after birth. (Ok, it's more complicated than that... it's all more complicated.) Synapses, though--of which you have about 100 trillion--are constantly being built up and torn down. Receptors built from thousands of amino acids get inserted into the synapse, only to be taken back out, maybe reused, but probably destroyed to provide raw materials for the next receptor. This takes minutes and it never stops. (That's why your brain is so hungry. Accounting for ~4% of your body mass, your brain consumes ~20% of your body's energy. That's why, when someone asphyxiates, the first organ to take damage is the brain.)

If there were 100,000,000,000,000 subreddits, creating and destroying thousands per second, each with posts and crossposts and comments every few milliseconds; rule changes every few hours; after weeks, months, or never; then you'd have something approaching the complexity of the human brain.

And that's just the brain. You also have to model how it interacts with the other body systems, which affect your mood and color your thoughts. (Try to think straight while hangry...)

THAT SAID, we could always build something similar and try to achieve similar functionality. But it wouldn't be a mind like ours; it wouldn't be a human mind. Even if it passed the Turing Test, even if it felt all the same emotions we do, even if it went full Blade Runner, it would still be a fundamentally different kind of consciousness from ours.

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