>>10943241Probably the most known theory is that it has to do with something called homeostatic plasticity. Neurons communicate either by exciting or inhibiting eachother. Evidence at the neural level suggests that the brain actively likes to keep a balance between excitation and inhibition to function properly and if this doesnt happen, the brain becomes either too chaotic or too lethargic and unsensitive to change. Learning however naturally leads to excitatory tendencies to the brain needs to rebalance itself (called homeostatic plasticity) and some people think this happens when we sleep.
Interestingly in neural networks, a type of process is used to improve learning which might be seen as equivalent to homeostatic plasticity. Usually networks learn by increasing connections between neurons that fire together but in this "homeostatic" process you decrease connections. When balanced with normal learning this tends to decrease spurious patterns and connections in the network. That process is only done when the network is cut off from its input which peoe have noted is kind of like the neural network is dreaming as youre letting it generate its own patterns by itself.
So thats a loose outline of a theory but ultimately dont think anyone really knows and we know so little about the brain that the theory is probably wrong in some significant way even if theres a grain of truth to it.
