> These individuals probably also exhibit diminished cognitive function as well.
I wonder how much of that is "the cerebellum is also involved in cognition" and how much of that is "with the rest of the brain picking up the additional load, there's less "processing power" available for other things".
My PhD adviser and I have had that debate a number of times. For the congenital case, we can't say one way or the other. But in the acute case, where there are localized lesions to the parts of the cerebellum thought to be involved in cognition, the effect seems to be primarily cognitive. From anatomical studies, we also know that there are "loops" formed between non-motor areas of the cerebral cortex and the cerebellum.
But couldn't that alternatively be explained by the cerebral cortex being able to act as a "backup" of sorts for the cerebellum, to the extent of "neglecting" its ordinary tasks? It would make sense if the brain were to "consider" motor control to be at a higher priority than cognition, and was designed as such. (Sort of like in a pinch a kitchen might use a cook as a dishwasher.)
I'm using wishy-washy words here, sorry. I don't know how better to explain it.
It's unclear whether the circuitry of the cerebral cortex has the ability to implement the function of the cerebellum (whatever that may be, which we don't really understand). I think we're a long ways off from answering that question.
Is there a way to check for this other than brain scans? My son is incredibly clumsy at 2.5years old and he fell off the bed when he was younger, perhaps 1 year old, and had a nasty bang to his fore head. He is a twin and his sister doesn't have as many falls as he does.
I wouldn't worry too much. I was very late learning to walk among other things and a doctor told my mom that I was "not exactly gonna be playing outfield for the Yankees". No Yankees yet but I ended up an all-state athlete, plus a two-sport college athlete. Most days I'm not totally stupid either.
Boys will be boys. I fell out of my bed at the age of 8! As far as I can tell, I am perfectly normal with excellent sense of balance now at the age of 30. As long as your son eats well, sleeps well, and is otherwise healthy, give it a few more years before you really start to worry.
Also, make sure to encourage movement (adults call it exercise, for kids is play). I used to be really clumsy as a kid before I got into sports as a late teenager.
Consider occupational therapy as well. It was very very helpful for my daughter, who was "behind the curve" with her gross motor skills. It's not just about increasing physical ability, either. Lack of core strength can affect the ability to sit still and focus as the body gets fatigued more easily.
Something tells me that going to your family doctor and saying 'I'm concerned that my son is missing some of his brain' isn't going to get you a referral to radiology, but who knows. If he hit his forehead really hard I'd probably take him in in case of a concussion, and that would probably tell you in some detail.
My 9 month old had his brain (and other organs) checked whilst in the womb during one of our ultra sound checks. BTW, it might be a country specific thing. I'm in the UK.
This is very unlikely to be the cause. If you're really worried about his clumsiness, I'd see a doctor -- there are lots of more common causes, many of them not even serious.
Or just "if there's something so wrong with your brain that the cerebellum is completely missing, odds are there is some hard-to-detect abnormalities in the rest of the brain".
Could it be that the cerebellum is merely a communication channel for other parts of the brain which are more focused on cognition. After injury one would not expect immediate re-routing of these channels.
For me, some of the way I think things through seems very physical to me. The sort of thing you do when you pick up lunch table objects and say, "Ok, this salt shaker is the web server, this fork is the firewall, and..." Except I'm more likely to do it with just gestures, or just thinking about placing things in an imaginary space.
I wonder how much of that is really enlisting the cerebellum versus it being an output-only thing. Perhaps nominally output-only devices do more. As in rubber-duck debugging or Flannery O'Connor's line, "I write because I don't know what I think until I read what I say."
I'm not very invested in this field, however, this "processing power" metaphor sound like those ideas "where people only use 10% of their brain". The brain doesn't work like that, it's not a general purpose computer. It's made up of several independent mechanisms, that have little to do with each other, and that have emerged at different points in evolution, driven by different forces. So their creation is rather chaotic.
I think that sort of misses the point of the metaphor as used here. If one big part of the brain is missing, and thus the mechanisms it enables are unavailable, some other part of the brain (at least in this case) makes up for it by providing an approximation of that mechanism. That other part of the brain is thus not able to perform whatever its normal function would be; even if it's doing double-duty, you expect that there's some capacity limit. When and if that deprioritized function involves reasoning, then you'd expect a drop in reasoning ability. Thus the "processing power" metaphor is simply saying that if a neuron is busy doing something, it can't also be busy doing other things.
I wonder how much of that is "the cerebellum is also involved in cognition" and how much of that is "with the rest of the brain picking up the additional load, there's less "processing power" available for other things".