Comment by blennon | Hacker News Reader

Comment by blennon | Hacker News Reader

This condition is known as cerebellar agenesis. A review of many of the case studies was done by a prominent cerebellum researcher [1]. Typically the individuals that survive past birth live relatively normal lives but with impaired motor skills which are slower to develop. Their abilities are remarkable given that acute lesions to the cerebellum result in much more significant impairments (e.g. not being able to touch your nose with the tip of your finger in one smooth, coordinated movement).

These individuals probably also exhibit diminished cognitive function as well. Only recently has it been recognized that the cerebellum is also involved in cognition [2]. It's interesting to note that you don't need a cerebellum to move or think, but the loss of it impairs both. Contrast this to damage to your motor cortex which can result in paralysis.

[1] Glickstein, M (1994). Cerebellar Agenesis. Brain, 117, 1209-1212. [2] http://www.ncbi.nlm.nih.gov/pubmed/23996631

> 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.

Well, given this development, I think it's fair to say there's something else that can implement the function of the cerebellum.

Something that can partially implement the function of the cerebellum.

True.

It might be sort of like switching from hardware rendering of video to software rendering.

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.

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.

I did take him at the time and they said he was fine but he was also so small he wasn't really coordinated or talking anyway.

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.

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.

Did your twins get ultra sound checks?

Inner ear problems sound like a far more likely issue. But, I would just talk to your pediatrician vs. soliciting random advice on the web.

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.

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".

Good point, hadn't considered that.

Ah, always look for confounders :)

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.

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.

Generally yes, but neuroplasticity does in fact exist: http://en.wikipedia.org/wiki/Neuroplasticity

Are you saying our brains follow the Law of Demeter?

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.

There is very interesting book called 'the brain that heals itself' that argues quite strongly against that.

A very interesting question!

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."

The article mentions:

"Problems in the cerebellum can lead to severe mental impairment, movement disorders, epilepsy [...]"

However this seems potentially much worse than the symptoms this woman without a cerebellum is experiencing. Is it theoretically possible that people with damaged but otherwise intact cerebellum to be identified at birth so that they can have their cerebellum removed completely? My thinking is that if you do it early enough, plasticity might allow other parts of their brain to take over and do the job better than the damaged cerebellum would be able to.

This is probably one of the reasons why I am not allowed to perform surgery without a license...

> This is probably one of the reasons why I am not allowed to perform surgery without a license...

Indeed :) A damaged cerebellum at birth might still be useful because it can fulfill some, if not all of the tasks it is supposed to. We don't know enough about this yet to really make any kind of call about it. For all we know, many people are borne with malformed cerebellums but never experience any problems, thus we just don't know about them.

I did see a documentary about some young girl with a brain problem. I can't remember exactly (severe form of epilepsy?), but they wanted to do something pretty severe to her brain, and do it within the first year, as it still had the neuro-plasticity to recover at that stage.

> This condition is known as cerebellar agenesis.

To tease you a little bit, I read this as

> This condition is known as being born without a cerebellum.

I don't know why we need a latin name for everything!

If I had to guess, I'd say it's because it's slightly faster, still makes sense if you have learned the right bits of Latin, and because it makes you feel smart.

More usefully it means doctors fluent in different languages have a very good chance of accurately describing conditions to each other.

It certainly makes it easier to find in a book or via search. You have one word for what it's called, instead of having some under "Born without a cerebellum," some as "Missing cerebellum," others in "No cerebellum," "Undeveloped cerebellum," etc.

Plus it's more convenient to say. Not a big deal for us, but to people who deal with crazy medical conditions all day long, describing each one in natural language would be imprecise and time consuming.

Though obviously it's not the reason it was adopted, it is kind of neat that using a dead language for scientific terms disambiguates them cleanly for the purposes of searching.

Any live language would have accidental matches (even quoted) where it's just the obvious thing to say, a la "born without a cerebellum".

To expand on that... it also solves the problem of technical terms evolving new nomenclature (or new meanings for old nomenclature!) over time.

not a dead language.. greek language is still alive and indeed it sounds like "born without a cerebellum" (but to be fair the syntax reminds of medical term)

Latin is a dead language, there has not been a native speaker for a very long time[1].

[1]:http://en.wikipedia.org/wiki/Language_death

It is still in constant use as the official language of the Vatican.

They keep having to invent new Latin words and phrases so they can discuss things like hotpants, which are brevíssimae bracae femíneae apparently.

Have a look here - http://usvsth3m.com/post/95991771713/hotpants-flirt-and-othe...

The cashpoint with Latin in comic-sans is awesome.

edit - translating from the latin, comic-sans is a pretty accurate font name.

having dead languages to imprecisely map to a word (but nobody knows that because no one really speaks the dead language) isn't any better. It also creates barriers and wasted time in learning the practice. The average individual has to deal with that folly even more when it comes to law.

It's better to have a shorter and noun form for referencing being born without a cerebellum. It's especially convenient for researchers who write about it and have to refer to being born without a cerebellum multiple times in a single paragraph.

It's better to have a shorter and noun form for referencing cerebellar agenesis. It's especially convenient for researchers who write about it and have to refer to cerebellar agenesis multiple times in a single paragraph.

Because it's much more convenient to have one single name for it in all of Earth's languages.

Perhaps you're thinking of taxonomy? English names for diseases don't set their names in other languages.

Does "cerebellar agenesis" sound English to you? Almost all things in medicine have almost universal names derived from Greek and/or Latin. Of course, until a few hundred years ago it was because those were the languages of science; these days the terms still fill the same purpose as they did back then - providing a common vocabulary for people from diverse origins.

Yes, "cerebellar agenesis" is an English term. Having Latin and Greek etymologies doesn't make the words Latin or Greek; "cerebellar" isn't even a legal Latin adjectival form.

Here are the titles of the wikipedia article "Cerebellum" in some other languages:

    Lillehjerne (Danish)
    Kleinhirn (German)
    Parengephaliδa (Greek - Παρεγκεφαλίδα if you can read Greek)
    Cerebelo (Spanish)
    Cervelet (French)
    Otak kecil (Indonesian)
    Smadzenites (Latvian)
    Kisagy (Hungarian)
    Beyincik (Turkish)
    Xiaonao (Chinese - 小脑)

Nobody's copying the English word (well, Tagalog and Malaysian are) -- they're all using their own native terms for "small brain".

Yes, the cerebellum is know as 'lillehjernen' in Danish and that word is the only word most people know for it. Nevertheless, doctors learn the word cerebellum so they can read what doctors in other countries write.

They also use the word amongst themselves. Googling for 'cerebellum ugeskrift for læger' gives plenty of hits. Likewise for 'cerebellar ugeskrift for læger'.

They might write 'agenese' instead of 'agenesis', though.

Well, I'd read it as "this condition is known as failing to develop a cerebellum". Even if everyone was born without a cerebellum and you were expected to grow yours by the age of 10, not growing one would be sensibly termed "agenesis".

Also, "agenesis" is greek, like most medical terminology ;)

Aha, thanks :)

I don't know why we need an english name for every keyword in programming languages!

Same with Greek! Can't wait for that "not-quite-finished-version-of-a-software-product" to be released!

> It's interesting to note that you don't need a cerebellum to move or think, but the loss of it impairs both. Contrast this to damage to your motor cortex which can result in paralysis.

This strikes me as akin to saying that you don't need a GPU to perform graphical processing, but not having it impairs your graphical processing capability. The brain wires itself throughout a human's development to take advantage of the specialization of its components and their parallelism.

Damaging an adult's cerebellum once those connections are in place would be the equivalent of removing a GPU before trying to play a game that has been developed to rely on it.

At least that's my simplified analogy drawn from my admittedly imperfect understanding of how the human brain and computers work.

I don't think anyone is anywhere close to "understanding perfectly how the brain works".

Trying to reason about the brain like it's a computer is a very common thing for computer scientists to do. Unfortunately, it's also mostly fallacious (since for a whole host of reasons, neurons don't work like integrated circuits), and simplistic analogies like cerebellum = GPU are probably not going to give much insight into what's really going on. I'm not saying "the brain is beyond human comprehension" or anything silly like that, just that you have to approach it from a biochemical context.

Sure, but the brain is a Turing machine, albeit with hardware acceleration of key functions (e.g., edge detection in the visual cortex). Mathematics, not chemistry, structures the problems it solves, if not the algorithms and heuristics involved. It's utterly fascinating to see how nature tackles the same problems that we solve independently using completely different tools.

What fills up that space? Liquid? Scar tissue?

Cerebrospinal fluid in this case and most; it's the general purpose volume-filler of the central nervous system.

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