Back when I was a neuroscientist I had a fun conversation at SfN (the largest neuro conf in the world) with a big up-and-coming researcher about the cerebellum. Her take was "I hate that thing. If I never have to read another paper about it again that would be great. It's dumb. I wish we could get rid of it." I wonder how she's feeling about it these days...
That attitude is a big problem. The cerebellum is where all the important stuff happens. In the lower mammals, the cerebellum is most of the brain. The cortex is just the back-seat driver sending goals to the cerebellum.
Bio researchers have done work on decorticated cats. "The cats ate, drank and groomed themselves adequately. Adequate maternal and female sexual behaviour was observed. They utilized the visual and haptic senses with respect to external space."[1] The cortex is optional for basic survival.
The cerebellum had been far too neglected in AI research. I used to refer to this as the "hole in the middle" of AI. We had the expert systems guys working on logical abstractions, and the behavior-based people working on near-stateless stimulus-response systems. Not much in the middle. That's what got me interested in legged running for robots. But it turns out that's better approached as a dynamics problem than as an AI problem, so that didn't lead to a cerebellum. Just a lot of banging on differential equations. On most practical problems, it's easier to engineer a special case solution than to develop something cerebellum like. So there's been low pressure to fix this hole.
The really important stuff in life is getting through the next 10 seconds without a major screwup. If that doesn't work well, and consistently well, survival is unlikely.
AI remains bad at this. Robots have this problem big-time. For self-driving cars, vast efforts have been required to make it work at all.
The cerebellum evolved first. The cortex is a relatively modern development. If we really knew how it worked and could make a good functional one for a robot, we'd probably have most of the parts needed for a cortex. But we don't.
When you see a paper like this, [2] you realize the extent of our ignorance. This is like cutting an IC into little chunks and doing a chemical analysis on each chunk to figure out what it does.
Decorticated cats have their whole midbrain, it's not the cerebellum that's doing all that. Also, the cortex is more dominant in primates. Decorticate humans can't do much of anything. Also, humans can live without a cerebellum:
My family has a history of cerebellar ataxia. If youve ever gone through knowing someone experiencing that its pretty horrible. The physical symptoms are bad enough but there seem to be common emotional and logical regulations that leave as the cerebellum dissolves.
Cool, but the direct link needs to be confirmed in humans. I recently recall David Amaral, who has done a lot of the great post-mortem work on the hippocampus and amygdala, telling me that it used to be thought that left and right hippocampi were connected by axon projections in humans just like they were in rodents, but this proved not to be the case.
\tangent In the spirit of understanding the mind in terms of the engineering of the day, the cerebellum's striated structure seems something of a DSP, for linear processing, especially where timing is involved.
There's a dramatic contrast between the sophistication of optogenetics, and the primitive hypotheses being tested: is this connected to that?
Does there need to be a direct connection, or could other parts of the brain use the cerebellum, when limear/timing is needed, for particular stages of processing, like a math co-processor?
e.g. Is it possible that instead of direct "wired" connections, there's a packet radio or UDP-like system, where neurons (or columns of neurons) aren't directly signalling, but passing on a packet of information to be shunted elsewhere in the brain.
> For about two centuries the scientific community believed the cerebellum (Latin for “little brain”), which contains approximately half of the brain’s neurons, was dedicated solely to the control of movement.
This is mind-boggling. Considering the chaotic nature of natural selection, why would such a big structure be neatly organized and compartmentalized like a computer processor?
