an autodidact meets a dilettante…

‘Rise above yourself and grasp the world’ Archimedes – attribution

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dyslexia is not one thing 4: the left and the right

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a one-sided view (the left) of the parts of the brain involved in language and reading processing

Canto: So we’re still looking at automaticity, and it’s long been observed that dyslexic kids have trouble retrieving names of both letters and objects from age three, and then with time the problem with letters becomes more prominent. This means that there just might be a way of diagnosing dyslexia from early problems with object naming, which of course starts first.

Jacinta: And Wolf is saying that it may not be just slowness but the use of different neural pathways, which fMRI could reveal.

Canto: Well, Wolf suggests possibly the use of right-hemisphere circuitry. Anyway, here’s what she says re the future of this research:

It is my hope that future researchers will be able to image object naming before children ever learn to read, so that we can study whether the use of a particular set of structures in a circuit might be a cause or a consequence of not being able to adapt to the new task of literacy (Wolf, p181). 

So that takes us to the next section: “An impediment in the circuit connections among the structures”.

Jacinta: Connections between. And if we’re talking about the two hemispheres, the corpus callosum could’ve provided a barrier, as it does with stroke victims…

Canto: Yes, connections within the overall reading circuit, which involves different parts of the brain, can be more important for reaching automaticity than the brain regions themselves, and a lot of neuroscientists are exploring this connectivity. Apparently, according to Wolf, three forms of disconnections are being focussed on by researchers. One is an apparent disconnection ‘between frontal and posterior language regions, based on underactivity in an expansive connecting area called the insula. This important region mediates between relatively distant brain regions and is critical for automatic processing’ (Wolf, p182). Another area of disconnection involves the occipital-temporal region, also known as Brodmann area 37, which is activated by reading in all languages. Normally, strong, automatic connections are created between this posterior region and frontal regions in the left hemisphere, but dyslexic people make connections between the left occipital-temporal area and the right-hemisphere frontal areas. It also seems to be the case that in dyslexics the left angular gyrus, accessed by good beginning readers, doesn’t effectively connect with other left-hemisphere language regions during reading and the processing of phonemes.

Jacinta: And it’s not just fMRI that’s used for neuro-imaging. There’s something called magnetoencephalography (a great word for dyslexics) – or MEG – that gives an ‘approximate’ account of the regions activated during reading, and using this tool a US research group found that children with dyslexia were using a completely different reading circuitry, which helps explain the underactivity in other regions observed by other researchers.

Canto: And leads to provocative suggestions of a differently arranged brain in some people. Which takes us to the last of the four principles: ‘a different circuit for reading’. In this section, Wolf begins by recounting the  ideas of the neurologists Samuel T Orton and Anna Gillingham in the 1920s and 1930s. Orton rejected the term ‘dyslexia’, preferring ‘strephosymbolia’. Somehow it didn’t catch on, but essentially it means ‘twisted symbols’. He hypothesised that in the non-dyslexic, the left-hemisphere processes identify the correct orientation of letters and letter sequences, but in the dyslexic this identification was somehow hampered by a problem with left-right brain communication. And decades later, in the 70s this hypothesis appeared to be validated, in that tests on children in which they were given ‘dichotic tasks’ – to identify varied auditory signals presented to different ears – revealed that impaired readers didn’t use left-hemisphere auditory processes in the same way as average readers. Other research showed that dyslexic readers showed ‘right-hemisphere superiority’, by which I think is meant that they favoured the right hemisphere for tasks usually favoured by the left.

Jacinta: Yes, weakness in the left hemisphere for handling linguistic tasks. But a lot of this was dismissed, or questioned, for being overly simplistic. You know, the old left-brain right-brain dichotomy that was in vogue in popular psychology some 30 years ago. Here’s what Wolf, very much a leading expert in this field, has to say on the latest findings (well, circa 2010):

In ongoing studies of the neural of typical reading, the research group at Georgetown University [a private research university in Washington DC] found that over time there is ‘progressive disengagement’ of the right hemisphere’s larger visual recognition system in reading words, and an increasing engagement of left hemisphere’s frontal, temporal, and occipital-temporal regions. This supports Orton’s belief that during development the left hemisphere takes over the processing of words (Wolf, p185).

Canto: Yes, that’s ‘typical reading’.  Children with dyslexia ‘used more frontal regions, and also showed much less activity in left posterior regions, particularly in the developmentally important left-hemisphere angular gyrus’. Basically, they used ‘auxiliary’ right-hemisphere regions to compensate for these apparently insufficiently functional left regions. It seems that they are using ‘memory’ strategies (from right-hemisphere structures) rather than analytic ones, and this causes highly predictable delays in processing. 

Jacinta: A number of brain regions are named in this explanation/exploration of the problems/solutions for dyslexic learners, and these names mean very little to us, so let’s provide some – very basic – descriptions of their known functions, and their positions in the brain. 

Canto: Right (or left):

The angular gyrus – which, like all other regions, is worth looking up on google images as to placement – is in a sense divided in two by the corpus callosum. Described as ‘horseshoe-shaped’, it’s in the parietal lobe, or more specifically ‘the posterior region of the inferior parietal lobe’. The parietal lobes are paired regions at the top and back of the brain, the superior sitting atop the inferior. The angular gyrus is the essential region for reading and writing, so it comes first. 

The occipital-temporal zone presumably implies a combo of the occipital and temporal lobes. The occipital is the smallest of the four lobes (occipital, temporal, parietal, frontal), each of which is ‘sided’, left and right. The junction of these two lobes with the parietal (TPO junction) is heavily involved in language processing as well as many other high-order functions.

Jacinta: Okay, that’ll do. It’s those delays you mention, the inability to attain automaticity, which characterises the dyslexic, and it appears to be caused by the use of a different brain circuitry, circuitry of the right-hemisphere. Best to quote Wolf again:

The dyslexic brain consistently employs more right-hemisphere structures than left-hemisphere structures, beginning with visual association areas and the occipital-temporal zone, extending through the right angular gyrus, supramarginal gyrus, and temporal regions. There is bilateral use of pivotal frontal regions, but this frontal activation is delayed (Wolf, p186).

Canto: The supramarginal gyrus is located just in front of and connected to the angular gyrus (a gyrus is anatomically defined as ‘a ridge or fold between two clefts on the cerebral surface in the brain). These two gyri, as mentioned above, make up the inferior parietal lobe. 

Jacinta: Wolf describes cumulative research from many parts of the world which tends towards a distinctive pattern in dyslexia, but also urges skepticism – the human brain’s complexity is almost too much for a mere human brain to comprehend. No two brains are precisely alike, and there’s unlikely to be a one-size-fits all cause or treatment, but explorations of this deficit are of course leading to a more detailed understanding of the brain’s processes involving particular types of object recognition, in visual and auditory terms. 

Canto: It’s certainly a tantalising field, and we’ve barely touched on the surface, and we’ve certainly not covered any, or very much of the latest research. One of the obvious questions is why some brains resort to different pathways from the majority, and whether there are upsides to offset the downsides. Is there some clue in the achievements of people known or suspected to be have been dyslexic in the past? I feel rather jealous of those researchers who are trying to solve these riddles….

References

Maryanne Wolf, Proust and the squid: the story and science of the reading brain, 2010

https://www.kenhub.com/en/library/anatomy/angular-gyrus

https://academic.oup.com/brain/article/126/9/2093/367492

https://en.wikipedia.org/wiki/Supramarginal_gyrus#:~:text=The%20supramarginal%20gyrus%20is%20part,of%20the%20mirror%20neuron%20system.

 

Written by stewart henderson

April 25, 2023 at 8:13 pm

dyslexia is not one thing 2: structural deficits

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the human brain- a very very rough guide

Jacinta: So we’re going to look at earlier ideas about dyslexia, before the recent revolution in neurology, if that’s not being too hyperbolic. These ideas tended to focus on known systems, before there were well-identified or detailed neural correlates. ‘Word-blindness’ was an early term for dyslexia, highlighting the visual system. This was partly based on the 19th century case of a French businessman and musician who, after a stroke, could no longer read words or musical notes or name colours. A second stroke worsened the situation considerably, eventually causing his death.

Canto: An autopsy revealed that the first stroke had damaged the left visual area and part of the corpus callosum, which connects the two hemispheres. It appears that what the man was seeing with his right hemisphere was not able to be ‘backed up’ by the left visual area, and/or connected to the left language area. The second stroke struck mainly the angular gyrus, a complex and vital integrating and processing region towards the back of the brain.

Jacinta: Yes, and before we go on, what we’re doing here is looking in more detail at the four potential sources of dyslexia set down at the end of the previous post. So in this post we’re focusing on 1. a developmental, possibly genetic, flaw in the structures underlying language or vision. 

Canto: Right, so there’ll be three more dyslexia posts after this. So this ‘Monsieur X’ case was one of ‘classic alexia’ or acquired dyslexia, and marked an important step forward in mapping regions in relation to the visual and processing aspects of language. Norman Geschwind described it as ‘disconnection syndrome’, when two brain regions essential to a function, in this case written language, are cut off from each other.

Jacinta: The auditory cortex became an important focus in the twentieth century, as researchers noted a problem with forming ‘auditory images’ – which sounds like a problem everyone would have! More specifically it means not being able to translate the images made by letters and phonemes into sounds.

Canto: Yes, so that a word like ‘come’ (which is actually quite complex – the hard ‘k’ followed by an ‘o’ which, orally, is neither the typically short nor long version, followed finally by the silent ‘e’ which has some quite strange effect on the previous vowel) would be quite a challenge. Perhaps the real surprise is that we have no trouble with it.

Jacinta: Yes, I prefer cum myself, but that’s a bit off-topic. Anyway, psycholinguistics, much derived from the work of Noam Chomsky, which came into prominence from the 1970s, tended to treat dyslexia more as specifically language-based rather than audio-visual. Taking this perspective, researchers found that ‘reading depended more on the linguistically demanding skills of phonological analysis and awareness than on sensory-based auditory perception of speech sounds’ (Wolf, p173). This was evidenced by the way impaired-reading children treated ‘visual reversal’ in letters (e.g p and q, b and d). They were able to draw the letters accurately, but had great trouble saying them (sounding them). This appears to be a spoken language problem, which carries over to writing.

Canto: Indeed, it highlighted a problem, which apparently had nothing to do with intelligence, or basic perception, but was more of a specific perception-within-language thing:

These children cannot readily delete a phoneme from the beginning or end of a word, much less from the middle, and then pronounce it; and their awareness of rhyme patterns (to decide whether two words like ‘fat’ and ’rat’ rhyme or not) develops much more slowly. More significantly, we now know that these children experience the most difficulties learning to read when they are expected to induce the rules of correspondence between letters and sounds on their own.

Phonological explanations of dyslexia have resulted in a lot of effective remedial work in recent decades, and a library of research in the field of reading deficits.

Jacinta: Yes, these are called structural hypotheses, noting deficits in awareness of phonemic structure, and phoneme-grapheme correspondences. And these deficits presumably have their home in specific neural regions and wiring. The executive processes of the frontal lobes may be at play, in terms of organised attention, the fixing of memory and the monitoring of comprehension, but also the more ‘basic’ processes of the cerebellum, involving timing and motor coordination. And co-ordination between these regions may also be an issue.

Canto: And, as Wolf points out, these structural hypotheses have sheeted home problems to so many brain regions – the frontal executive function region, the speech region close by, the central auditory region, the language and language/visual integration regions, the posterior visual cortex and the cerebellum – that it would be fair to say that ‘many of the collective hypothesised sources of dyslexia mirror the major component structures of the reading brain’ (Wolf, p176).

Jacinta: Which sounds pretty serious. Why is it happening? And why not for others…?

References

M Wolf, Proust and the squid: the story and science of the reading brain

https://www.kenhub.com/en/library/anatomy/angular-gyrus

 

Written by stewart henderson

April 16, 2023 at 4:50 pm

Pourquoi science? – inter alia

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hussey274

So as I approach my sixtieth year I’m in a mood to reflect on my largely wasted, dilettantish life (at least seen from a certain perspective… ).

It seems to me that my two older siblings and I were largely the products of benign neglect, if that’s not too unfair to my parents, who seemed largely pre-occupied with their – highly dysfunctional – relationship with each other. Anyway this neglect had its advantages and disadvantages, and it was offset by at least one key decision of my mother (by far the dominant parent). She had us taken to the local library once a fortnight to borrow books, and there were always books aplenty in the house, including at least two sets of encyclopaedias. So from the age of six or seven until I left home, the local libraries became a haven.

From almost the beginning though I felt a difference between learning, which was a thrill, and school, which I suffered in silence. My first strong memory of school comes from grade one, when I was five or six. My teacher asked me to read from our class reader and I had to tell her that I’d forgotten to bring it from home. She blew up at me. ‘You’ve forgotten it again! What’s the matter with you? How many times have I told you,’ etc etc. I was extremely humiliated. I was learning that I was vague, forgetful, disorganised, and it was all too true. Shortly after this, I arrived at school and discovered I’d forgotten my reader again. I was so scared I hid in the bushes until break time, when I rejoined the class unnoticed, apparently (though probably not). I remember the sense of being defiant and tricksterish.

It’s funny that I’m now a teacher who checks students’ homework and has to admonish those who don’t do it, because as a kid in primary school and later in high school, when the issue loomed much larger, I never did any homework. Not once, ever. I even got caned for it in high school. And suffered endless screaming fits from my mother when the matter was reported back to her. I remember many sleepless nights fretting about how to survive the next day’s questioning, but still I was unable or unwilling to comply. I spent a lot of my school days staring out the window, daydreaming of freedom. One day I watched a tiny bird – a hummingbird, I thought, but we have no hummingbirds in Australia – hovering a bit driftily above some bushes, for ages and ages. What an ability, what a perspective it had! And yet it felt constrained to hover there. Maybe only humans could free themselves from these ‘natural’ constraints.

funny-math-answers-2funny-test-answers-smartass-kids-21

 

I concocted an idea for a novel, which I confided to my sister, of schoolkids rising up and throwing out the teachers, establishing an ‘independent state’ school – an idea I probably took from Animal Farm. She was very enthusiastic, probing me on the details, assuring me it would be a best-seller, I would become famous. I became briefly obsessed with contemplating and planning the takeover – the secret meetings, the charismatic leader, the precisely organised tactics, the shock and dismay of our former masters, the nationwide reaction –  but of course I soon stumbled over the outcome. Surely not Animal Farm again?

I learned over time that Elizabeth, our town, was the most working-class electorate in South Australia, with the largest percentage of labor voters in the state, and possibly even the country. Of course, one had to take pride in being the biggest or the most of anything, but what did it mean to be working-class? Was it a good or a bad thing? Was our family more or less working-class than our neighbours? I was discovering that interesting questions led to more questions, rather than to answers. That, as Milan Kundera wrote, the best questions didn’t have answers, or at least not final ones. Of course, the provisional answer seemed to be that it wasn’t good to be working class, or middle class, or upper class, but to move beyond such limitations. But I was learning, through my library reading, which increasingly consisted of Victorian English literature for some reason, that class wasn’t so easy to transcend.

I continued to struggle as my schooling moved towards the pointy end. Classmates were dropping out, working in factories, getting their first cars. I was wagging school a lot, avoiding the house, sleeping rough, drinking. My older brother started an economics degree at university, probably the first person in the history of my parents’ families to do so as the prospect of university education was opened up to the great unwashed, but I was unlikely to be the second. I recall wagging it one afternoon, walking to the end of my street, where the city of Elizabeth came to an abrupt end, and wandering through the fields and among the glasshouses of the Italian marketers, armed with my brother’s hefty economics textbook, and getting quite excited over the mysteries of supply and demand.

And so it went – I left school, worked in a factory here, a factory there, went on the dole, worked in an office for a while, got laid off, another factory, moved to the city, shared houses with art students, philosophy students, mathematics nerds (whom I loved), wrote volumes of journals, tried to write stories, ritually burned my writings, read philosophy, had regular bull sessions about all the really interesting things that young people obsess about and so on and on. And I haven’t even mentioned sex.

I’d always been hopelessly shy with the opposite sex and wrote myself off as eternally poor and inadequate, but I loved girls and fantasised endlessly. I felt guilty about it, not because I thought it immoral – I never had any moral qualms about sex, which made it all the more easy to dismiss religions, which all seemed to be obsessed with regulating or suppressing it. I felt guilty because sexual daydreaming always seemed the lazy option. I was like Proust’s Swann, I would tire easily from thinking too much, especially as those great questions never had any easy or final answers. So  I would give up and indulge my fantasies, and even the occasional unrequited or unrealistic passion for real female acquaintance. I remember hearing of a celebrated mathematician who would wander homeless around the USA I think it was, couchsurfing at the homes of mathematical colleagues male and female, inspiring them to collaborate with him on mathematical papers, so that he held a record for the most papers published in peer-reviewed journals. An attractive female colleague laughed at the idea of an affair with him, because apparently everyone knew he was entirely asexual, had never been heard to even mention sex in his life… Could this be true, I wondered, and if so, how could I create for myself a brain like his? It seemed to me that Aristotle was right, the pleasure derived from certain types of contemplation was greater than sexual pleasure (though dog knows I’d hate to forgo sex). I’d experienced this myself, grappling with something in Wittgenstein, reading a passage over and over until an insight hit me and set me pacing around my bedroom all night long talking to myself. But maybe it was all bullshit.

So now to get to the heart of the matter – pourquoi science? As a youngster I read novels, and sometime works of history – one of my first big adult books was a very good biography of Richard III, which I read at 14, and which came flooding back when Richard’s body was miraculously discovered recently. But I never read science. At school I quickly lost track of physics and mathematics, while always being vaguely aware of how fundamental they were. Through philosophy in my early twenties I started to regain an interest, but generally I’d resigned myself to being on the arts side of the great divide.

One book, or one passage in a book, changed this. The book was Der Zauberberg, or The Magic Mountain, by Thomas Mann, which I read in 1981. This was the story of Hans Castorp, a young man in his mid-twenties, as I was when I read it. As a tubercular patient, he was sent to a sanitarium in the Alps for a period of enforced idleness, where he encountered a number of more or less interesting characters and was encouraged to grapple with some more or less interesting ideas. Wrapped up on his loggia, he was reading some books on fundamental science, and fell into contemplation, and in a passage of some fifteen pages he asked himself two fundamental questions, both of which branched off into a whole series of sub-questions (or so I remember it). They were: What is life? and What is matter? And there was something about the way Mann animated this Castorp character, as ordinary a fellow as myself, and made me identify with his questioning and his profound wonder. It just flipped a switch in me. These were the questions. They could easily fill several lifetimes. No reason ever to be bored again.

93080-M

I immediately went out and bought my first ever science magazine, Scientific American, and throughout the eighties I bought each monthly issue and read it cover to cover, not always understanding it all of course, but gradually building up a general knowledge. Later I switched to New Scientist, and nowadays I read the fine Australian magazine Cosmos, as well as listening to science podcasts and reading the odd blog. I’m far from being a scientist, and I’ll never have more than a passing knowledge – but then, that’s all that even the most brilliant scientist can hope for, as Einstein well knew.

But here’s the thing – and I’ll expand on this in my next post. It’s not science that’s interesting – science is just a collection of tools. What’s interesting is the world. Or the universe, or everything. It’s the curiosity, and the questions, and the astonishing answers that raise so many more questions. For example – what is matter? Our investigations into this question have revealed that we know bugger all abut the stuff. And when we were young, as a species, we thought we knew it all!

Next time, I’ll focus more deeply on science itself, its meaning and its detractors.

camps-image

 

Written by stewart henderson

March 12, 2016 at 8:30 am