A Theory on Autism's Cause

Post Reply New Topic

I put this on my blog but I'll copy it here. I know that not everyone will subscribe to this idea but it seemed to make sense to me and fits what I know so I thought it might stimulate some useful thinking. I seem to ramble a bit but it's all to explain why I thought of the theory.

On Autism, Eggs, The Cosmos, Infants Counting and Entropy

An Egg is a low entropy object. It is ordered and structured. If that order and structure is disrupted it stops doing what it is intended (as a reproductive structure) to do (and becomes breakfast). Entropy is chaos, crack an egg and it becomes more chaotic and entropy increases. The egg is commonly used to explain what low entropy can mean. In short low entropy means order.

The observable universe has it's share of high entropy and low entropy examples and as a general rule entropy increases. Things break down from low entropy to high entropy. Only gravity, crystals and life seem to actively buck this trend although crystals and life require energy to be formed.

Cosmologists talk about the universe expanding. That not only can things move away from each other, that the universe itself is expanding like a giant rubber band being elongated. They theorize that as the universe expands, energy will become so diffuse that all the stars and galaxies will eventually (billions and billions of years from now) fall apart and cool off. Their structure drawn asunder by space expanding (sort of). Entropy becomes the winner.

It often is said that each person's own personal universe consists of what is in their own mind. This is of course a metaphoric thought but still compelling. Just like the universe it has it's structure. In fact the structure in a human's brain may be more complex than the whole rest of the universe (counting all the cellular complexity).

Just like the universe, man once thought the mind to be relatively simple. The more man peers out in telescopes into the universe the more structure he sees. In the same way, the more man investigates the mind, the less of a jello like grey blob it proves itself to be.

It would be easy to imagine the mind as a series off nondescript neurons that self assemble connections to each other as input from the senses are provided to them. If this were true though, everyone's mind would be completely different than the next person's. That is not the case, while there is individuality to every mind, there are structures. Some control the hands, some manage vision, some handle danger, from conception these structures are slowly forming as the brain grows and they don't stop forming, maybe ever but most notably until a person is in their mid twenties (then we start killing it with alcohol). These structures are evident in that an infant can count logarithmically, meaning it will notice a change from one item to five, then ten then twenty. No one teaches them this skill. In order for a baby to do that, they must have a structure in place that is formed in their brain. A structure that is meant to handle numbers in that way.

Now what happens to those structures when space expands faster than the structures can form? Entropy increases, chaos. How could that happen in a brain? So far I've been explaining what thoughts are leading to my thought on Autism.

An Autistic child's brain is on average 2% larger than a normal child's brain at age 2. Some go all the way to 10% larger. Then by age 5, although their brains stay larger than average, the growth rate slows. Normally people would think that a bigger brain would be a good thing but perhaps not when the brain is trying to form and grow at the same time. The structures may be diffused by the unusual expansion of the tissue they are forming in.

As evidence some autistic children act fairly normally until about age two when quickly and dramatically they loose social and verbal function. Now to be clear, some children's autism is observable nearly at birth by telltale behaviors but commonly enough, major symptoms can arise very quickly. Something that was there, breaks. Some structure that used to exist stops working.

Which structure breaks and how much function is lost is random and variable from one child to the next. Perhaps if the expansion is minor, with some work the brain can repair the structure over time. Then again if the expansion of tissue is severe in just the wrong place, a vital cognitive structure could be rent apart, never to reform.

Then there are those that are savants. How does this happen? This falls a little more intuitively under the idea that a larger brain would seem to be better. Some structures may be disrupted only marginally or at their periphery. The holes are repaired and either give rise to more computational potential in the structure or a different but still valid structure. In most cases these are an autistic person's quirks. In some they may disrupt filters that prevent a person from taking in details that are normally thought of as irrelevant. In some they may allow the person to more actively manipulate their mental process. There are any number of ways that the expansion could do some good over time as the brain struggles to catch up.

This would seem to match the pieces of the puzzle that I am aware of. This could be testable by looking at an fMRI and seeing which parts of an autistic 2 year old's brain are bigger than average and then seeing if the corresponding parts are linked to where they later show disfunction. It also may be possible that the whole brain grows and the amount of disruption only occurs in some of the more delicate structures of the brain.

Chaudywogbaaga

Last edited by Emmett on 23 May 2011, 2:40 pm, edited 1 time in total.

But my head grew at a normal rate.

On the whole, that may be true, but a couple million cells here and a million there would hardly be noticed overall. In addition 2% bigger would be quite difficult to gauge without a CT scan or a MRI. Maybe you've already had those done?

I would even go so far to say that even if your brain were 10% bigger at age 2, If you rolled the dice just right, you might have 0 to minor impairment or severe impairment based on how the tissue grew.

It's just a theory though, they would have to do a lot of research to prove it.

I asked my parents about the brain scan thing and they said "no". I had my head measured by a doctor.

Oh absolutely right. The theory also doesn't explain the root cause of the overgrowth, which I would only look at as a useful endeavor if the growth was known to be the culprit.

The overgrowth is caused by overprofileration of neurons during corticogenesis. Haven't you read this paper? http://archneur.ama-assn.org/cgi/content/full/64/7/945 I don't think your theory is quite right.. the wiring of the brain is based on signaling which can adapt surely to differences in how the cortical tissue expands, because the right neurons will still be producing the right signalling molecules to "know" where they are supposed to wire up.

It doesn't explain why you get autism rather than something very much like a traumatic brain injury or cerebral palsy. Autism is not just plain damage--it's not "entropy"; it's order of a different sort.

My personal origin theory? The brain is autistic because the DNA tells it to be. The autistic bits of the DNA aren't damage; they are parts of the normal human gene pool, floating around because they are beneficial in small doses, when a person has only one or a few of them. In the autistic person, there's simply too many of those genes, leading to a "too much of a good thing" effect and the typical impairments of autism.

Callista, i agree completely with that assesment, i have expressed the same views in the past. natural selection is not perfect, some small variations can add up in one person and be deleterious (as in lowering reproductive & survival fitness, not an objective measure of the phenotype itself). So we get stuck with evolution's baggage of the evolution of the human brain, in a way.

I haven't read that paper yet, just skimming I'm trying to understand why the added white matter would make intercommunication more limited since the white matter handles intercommunication. I think I must be reading it wrong at the moment. I'll have to go over it when I have more time.

On the brain being based on signaling, that can only be partially true. If the brain was only based on signaling then infants would have no neural programming whatsoever. There must be structures set up in the neural wiring that make certain regions of the brain handle certain jobs and since a newborn can do some of them to a limited extent, there has to be some "instinct" that starts them down that path. That instinct could be in structured wiring of the neurons.

This is telling "overgrowth was part of a pathologic process that disrupted the development of normal brain structure and function in autism." So the thought isn't unprecedented.

On Autism being order of a different sort, yes, but in this theory it would be an order based on the brain having to find it's own solutions rather than instinct providing those solutions as part of the growth process.

On the DNA telling the brain to be Autistic, yes, maybe. It would either be the DNA or epigenetic (actually I think the paper DevilInside referenced points to epigenetic causes). And yes it could easily be a normal growth process being repeated several times and the over repetition would cause the excess growth. A gene repeated five times worked with dad, and six times worked with mom but when they combined and made a gene with it seven times things started to pull apart because it was too much.

There is something to this in part.

Scientists believe that the part of the brain called the amygdala is fairly central to autistic brain differences. And in males (not sure about females), autistic people have a fully grown amygdala by age 8, whereas NTs have a fully drown amygdala at "late adolesence". The difference is, by adulthood, that this part is the same size, but the autistic's brain has considerably fewer neurons, and so connectivity with other parts of the brain is reduced, and the function of the amygdala is reduced.
Generally, the amygdala is central to both emotion and memory, and links emotional learning.

Being based on signaling doesn't have to contradict what you said about genetic wiring.. it is just that the system is flexible enough to handle overgrowth because the right regions are still interconnected, it's just that there is more white matter tracts running between the regions and it is my own belief that the increase in grey matter per region just means that more details are encoded and sent to higher regions.. making a case for the "intense world theory" of autism, where the brain encodes too much detail to maintain its proper holistic processing of the sensory and motor "data".

There is another thing.. i have recently come to doubt the notion that autistics have a deficit in global processing or region interconnectivity.. nothing in the neurobiology suggests that there is a deficit in global connectivity, in fact there is too much connectivity! Most of the major brain tracts seem to be thicker and more elaborate in autism. Also, there is the fact that autistics score superiorly on measures of general intelligence, something which directly contradicts the notion that there is a deficit in global brain processes. I believe we still have some way to go towards understanding autism, but i am still leaning towards the "it's just neurodiversity, not pathological processes" side of things. That is the beauty of evolution, it can naturally handle diversity because the genetic and epigenetic processes work in such a way as to still be able to wire up a workable brain despite neuroanatomical differences arising from mutations in genes that regulate neurogenesis processes.

So to conclude, i believe autism is just a natural variation of brain development processes.

I'd agree that it doesn't seem to be a throughput issue. My contention is that it is a signal processing issue. Structures in the brain that are normally there to translate or process signals have been pulled apart by excess growth or interrupted in their pattern no longer do the job they were there to do. The autistic person has to cope with this by making their own processing system from what is left or from scratch. Oh and I am reading through the article and although they do discuss the overproliferation of nerve cells, I think the concept of the growth outpacing the formation of larger structures that in the end encode for "instinctive behaviors" (face recognition, language cognition, etc.) is still a novel one.

I think in it's higher functioning forms Autism could be considered neurodiversity in action but when it's debilitating I would think of it as a pathology. After all isn't any pathology a creature not being able to function properly or at all?

it all depends on what standards you impose on the creature.. for example, other animals do just fine without being able to talk or understand language, so why do we consider a homo sapiens who can't do these things more defective then an animal who has the same "defect" absolutely speaking? i have a very strong aversion to the idea that there is somehow a barrier where autism severity becomes a pathology, just because we don't yet understand brains which are wired this differently. I also disagree with the idea that any part of neocortical processing is "instinctive", it is known to be a very adaptive, learning system which only has a general wiring diagram of the regions, which then get filled in by experience. it just happens to be that most people have a wiring system that easily learns language and social rules, not because these things are pre-wired though. The flexibility of the neocortex is a great achievement of "design" by natural selection.

I will admit though that there is a possibility, as is hinted at by that article i linked, that there are deficits in cortical inhibition and signal insulation in some cases of autism. But i would argue that these are a minority of cases where there is an additional genetic 'hit' of faulty development of inhibitory circuits. This might be the core deficit in autism, which is not directly caused by the neordiversity, but by an additional genetic difference. These are not new ideas, check out the work of Manuel F. Casanova if you're interested.

I dispute that other animals do just fine if they can't talk or understand language. Animals don't speak or understand the human languages (unless specifically taught by humans) but they sure do talk and communicate in their own languages. I think a deaf bird or bird that couldn't warble would be at a huge-possibly fatal- disadvantage. It is animal cruelty to debark a dog. It isn't a problem for us if animals can't use their language (which is why some people cruelly debark dogs) but it is most definately a severe disability for them.

Not being able to communicate or understand communication is a serious liability no matter what your species is. In species other than ours, it would probably lead to death fairly quickly. Humans have figured out alternative ways of communicating for people who can't talk. But not being able to understand presents a far larger problem. And it would in any animal. Consider the bee that can't follow signals from the colony. Or a gorilla who didn't understand it was being told to leave or be attacked. Or a bird who couldn't hear the "danger" warbles of the other birds. Not being able to understand the language of your species may be even a more dangerous liability than not being able to communicate (which at least in our species there are workarounds) and it applies to any species.

I guess i should have thought that one more through.. however, it still stands to reason that human society has come to a point where the standards imposed by natural selection have become irrelevant for the most part.. people can thrive in all sorts of special niches even if they have something that would be considered a disability in the wild.