My answer to “what is the cerebellum doing” fits in one sentence:
I think the cerebellum sits there, watching ≈300,000 different signals in the brain—including signals within the brain, signals going down to the periphery, and signals coming back up—and it learns to preemptively send those same signals itself, but a fraction of a second earlier.
More details at Section 4.6 here.
I don’t think my proposal counts as either “forward model” or “inverse model”—or at least, it seems pretty different from what people are usually talking about when they use those terms.
I claim that my proposal is consistent with everything known about the cerebellum. (Happy for criticism! Come at me!)
I don’t like dmac’s proposal here (if I understand it) because I’m not sure how those models get into the cerebellum. In particular, if they’re learned, then I don’t understand what’s the ground-truth that they’re learned from. Or if they’re in the genome, that doesn’t seem compatible with cerebellar anatomy, and doesn’t seem compatible with the cerebellum being helpful for controlling a jet-ski or controlling a six-legged videogame character or lots of other things that were not in the ancestral environment. Right? Or sorry if I’m misunderstanding 