Monday, 21 May 2012
It’s been an exciting week. On Friday, a small group of us launched a campaign to raise awareness of children’s language learning impairments (RALLI). We’ve been fortunate to have had considerable help from TeamSpirit, an agency whose expertise in marketing and advertising has been invaluable. With their assistance, we’ve set up a YouTube channel, which has kicked off with some professionally-made video shorts to introduce the campaign. But we don’t have funds to continue with a lot of expensive professional services, and so our plan is to post a mix of content on the site, including some videos made by the RALLI team. We are four academics and a speech-and-language therapist, none of whom has any expertise in filming, but the TeamSpirit folks were reassuring. What we needed was a digital flipcam, which would allow us to film ourselves in high definition video, download to the computer, and upload to YouTube. Easy peasy. Or so I thought. Before I began this exercise, I was a straightforward atheist. Now I believe in supernatural forces, but they aren’t benign.
The camera arrived in the post and looked great - same size as a mobile phone. I studied the manual. There was a battery. There was a slot labelled ‘battery compartment’. But there was a problem. The battery did not fit in the battery compartment, whichever way I tried. I grumbled to my PA that we’d been sent the wrong battery. She discovered a bit of the manual that explained how to insert the battery - in a quite different place. I left her to play with the camera while I went off to prepare a lecture, as she was clearly more suited to this than me. She emailed me to say that the camera worked well, but there was a snag. It stored exactly 30 seconds of footage. Should you want more than this, you had to buy a memory card. This is what went in the ‘battery compartment’. So, my plans for starting filming were foiled.
Onto the Kodak website. Astounded by how much I’d have to pay for a memory card. Realised I’d also need some kind of tripod to stabilise the camera when filming myself. Registered on the website, put in an order, tried to pay with Paypal, password rejected. Having assumed various emails from Paypal were spam, I was now uncertain as to whether or not my recorded password was still valid. But I wasn’t going to get a chance anyhow, as my failed password had somehow aborted the whole operation. Too busy to start again, so decided I’d take a look in Currys to see if I could buy memory etc.
The Currys option was the only positive thing to happen. Found a dinky little cushion thing that you could screw your camera into that cost far less than a tripod and worked as well. Also found that, as I didn’t plan to record hours of footage, I could buy a small memory card much more cheaply. So I was ready to go except for one thing. I needed an external microphone.
We had had a clearout of our lab a few months ago, during which we’d found a huge cache of microphones. For years we did research on language disorders that involved making good quality tape-recordings of children, and we had clip-on microphones, boundary microphones, big microphones, small microphones, none of which had been used for years. However, they had all been carefully put away. Somewhere. I thought I was getting close when I found a box full of headphones, but no. Several boxes later, I gave up. I wonder if other people have boxes full of cables that connect together things that you have never used, have no idea what they’re for, but can’t bear to throw away.
Eventually, a savvy member of my team arrived and located a boundary microphone, which I took home with me to experiment with over the weekend. Well, I guess this microphone had once been good, but it had lived in a box for about 8 years. I assumed that the little round battery in it was now well dead, but there were a couple of spare batteries still in their original packaging. Like most contemporary packaging, this was designed to give you the impression that if you attack it with fingernails, you might get in, when in fact this is not the case. The only result is a broken fingernail. What is needed is scissors, and so I now went on a scissor-hunt. Eventual success, though why scissors should be in the fruit bowl I do not know.
No indication as to which way round the battery should go, and I’d made the mistake of removing the existing one without checking. Tried new battery one way up. Nothing. But now a problem. The battery sat happily in the battery hole and did not want to come out. Tried fingernails, tried prodding with nail-scissors. It wobbled, but it wouldn’t budge. Gave to husband. He tried fingernails, and tried scissors. Then he had a remarkable insight. “What we need,” he said, “is a magnet”. This seemed to me no more than a theoretical speculation of no practical relevance. But he went further, and demonstrated his true genius in lateral thinking. “We need the little red man.” The little red man is a fridge magnet that we’d been given for Christmas. Downstairs to the kitchen again. The red man’s magnetic feet proved to be the perfect size for extracting little round batteries from microphones. We removed the battery. We rotated the battery. We reinserted the battery and plugged the microphone into the flipcam. Made a recording. Couldn’t hear any sound. What we now needed, clearly, was headphones. Headphone-hunt ensued. Headphones eventually located in the bedroom. Plugged in. Well, there was sound, but it was very faint. I tried modifying the controls on the flipcam to improve the gain, but that had minimal effect. Here my amateur knowledge of technology failed me. If it was faint, could it mean that the battery was running out of juice? Husband thought unlikely but we did have one more spare battery to try. Another assault on packaging with scissors and we were in. We had another go with red Pete’s feet, but the new battery didn’t work at all. At this point it was getting late and husband was impatient to watch another episode of Breaking Bad (highly recommended: we are on series 3), so I gave up for the night.
Next morning decided to look in the geological specimen cabinet to see if I could find an alternative battery. This is an amazing piece of furniture that we picked up in a country auction about 30 years ago. Its original function was to store bits of rock, but it is a godsend for a hoarder, as it allows you to hoard your useless objects in labelled mahogany drawers. One drawer is called Batteries. The problem is that the batteries that live in it tend to be very old, but I did find some that were small and round and labelled as “For use only in NHS hearing aids.” Husband, who has a hearing aid, denied all knowledge of them. Ever optimistic, I decided to try one in my microphone, feeling ever-so-slightly wicked at disobeying the stern injunction on the packet. The battery fitted in the microphone slot very snugly. I tried recording. I got a signal, but it was even weaker than before. Oh well, I thought, maybe I should just buy a new battery. But then I had a problem. The snugly fitting NHS battery was wedged in. Even the full force of red Pete’s feet would not budge it. I felt that God was punishing me for misappropriating NHS property and sadly decided that the boundary microphone would have to be ditched, and I should just get myself a clip-on microphone (which was what TeamSpirit had originally recommended….).
Off I trotted to Currys. “No”, they said, “We don’t do microphones. You could try Maplins on the Botley Road.” This entailed a trip in the car, but, after standing for 10 minutes in a queue while the extraordinarily helpful Maplin’s staff explained some complicated electronic device to a customer, I was armed with my microphone and ready to go. Quick test when I got home and it worked! Excellent clear signal. So I should be able to make the two short video clips that I had undertaken to do.
Now my only problem was to perfect a three-minute spiel and record myself saying it in front of the camera. Well, there was another problem, which is that my usual weekend appearance is scruffy. I do scruffy very well. It’s my natural state. But if I was going to be recorded for posterity, I needed to try and look professional. I realised that only my top half would be visible, so put on smart top, jewellery and make-up. Husband wandered in at some point: surprised to see me dressed up but clearly thought I had just forgotten to change from track-suit trousers, which says much about my usual level of absent mindedness. Arranged camera on a stepladder to capture head-and-shoulders region, checked light levels, sat in chair, breathed in ready to start spiel, and … the phone rang. Blood transfusion service, wanting me to make an appointment to give blood. Go downstairs, find diary, make appointment. Start again.
The thing about talking in front of a video for three minutes is that it’s quite easy to do it for about two minutes, but then you snarl up. I had two takes that were near-perfect but where I then descended into gibberish. There was also one take where the top of my head was chopped off, and another where I forgot to plug in the microphone. But eventually, I had a version with just a minor stumble in the middle which I decided I could live with. So now, I just had to import it into my computer. Quick hunt for the instruction manual, eventually located underneath a newspaper. Cunningly designed camera has USB connector that you can pull out of slide slot: neat! You put it in your computer, which allows you to download the software that you need to edit your video. This gives instructions for yet other software that you need to find on the web. You download that and restart the computer as instructed. You then get a cheerful message to tell you that there’s a new version of your software, and would you like to download an update now. “No I would not!” I say sternly to the screen, determined to press on now I’ve got started. I’m confused as to the distinction between the two bits of software, but eventually manage to download my video. It’s looking good. Except the audio starts about three seconds before the video. I try again. Same story. I look at video on the camera: audio and video perfectly synchronised.
Decide I need coffee, but we are out of coffee, so nip across the road. Weird look from shopkeeper reminds me that I am make-up and jewellery on top half and tracksuit on bottom half. Coffee in hand, I regroup. No advice on out-of-sync films in the manual or on the website of the camera-maker, which is complex, confusing and looks unlikely to resolve my problems. Try Google. There seem to be only a tiny handful of people out there who’ve had the same problem, and the replies they’ve had are not encouraging. One man had shot 20 hours of film before realising the problem, so I reckoned I was lucky in comparison to him. One suggestion to him was to get into an editing program that would allow him to shuffle along the audio track. I dimly remember using some video editing software in the past that allowed me to separate the audio and video stream on a file. Hunt through all my software, and locate Windows Moviemaker. This is encouraging, except it doesn’t seem able to read mp4 files.
In the back of my mind, there’s a concern that maybe the problem is due to the microphone. Now, this is what happens to me when I encounter a succession of obstacles: I start calm and logical, but I then start to think that there’s a malign force out there chuckling over my misfortunes, and I lose the plot and move over to magical thinking. If the problem was the microphone, then my logical brain tells me that the video should be out of sync when viewed on the camera. But a little voice in my head is telling me I should try with a different microphone, and so off I go on a futile and time-consuming exercise. I have another microphone that’s attached to a headset. So I unplug the recorder from the computer USB port. In response, computer gives me blue screen of death. Switch off computer. Reboot. Relieved to find it still works okay.
So I return upstairs to my living room to record two new brief segments, one with original microphone and one with headset microphone. I come downstairs, I plug camera into USB port. Blue screen of death returns. Reboot computer. It won’t start. Realise that this might be due to camera in USB port. Remove camera. Computer starts OK. Gingerly put camera in USB port. This time it’s okay, and I download my two trial clips. Both download okay. But when I play them, I realise there’s a fatal flaw to my test. I recorded clips with me talking, but did not record my face. So I have no idea whether or not the audio is in sync with the video.
Upstairs again to re-record. Ultimately, this futile test confirms that both microphones give an in-sync film on the camera, which mysteriously transforms into an out-of-sync version on my computer.
I have a faint memory of things called codecs, which determine how audio and video is converted into a digital form. Maybe I don’t have the right codecs. At this point, a more sensible test occurs to me. I should try downloading on to a different computer. Husband who is peacefully working in his office at top of the house is willing to lend me a laptop, which I carry to my office at bottom of house. It takes a very long time to boot up, and once it’s done that, I can’t get the mouse to work. Try pressing buttons etc. No joy. Further consultation with husband. Decide to replace battery in mouse. We have batteries, but they are defended by packaging. Further hunt for scissors. Get battery. Replace battery. Mouse now works. Plug in camera. Download software. Restart. Get message telling me to download updated software and decide this may be a good idea, so do that and again restart. This is a computer that takes a good 5 minutes to boot up and to shut down. Make a cup of tea while all this is going on. And, joy oh joy, when I have got software installed and downloaded the video, it works. It is in sync! I have to edit it to chop off the first and last bits, where I am walking from the camera to the chair and back, and so I find the manual which explains how to do that, but I’m in a hurry, as we are going out for the evening, and somehow, I manage to do the opposite of what I intended, so am left with just the end of the film, which is a bit I wanted to discard. Still, I think, we’re getting there. Tomorrow is another day.
A new day dawns. I download the film to husband’s computer one more time. This time I do succeed in selecting the right portion to save, and create a file that we’ll be able to download to YouTube. But I’d really like to back it up on my computer, and there’s a problem. It’s too big to email, too big for Dropbox, and won’t fit on a memory stick. I used to have several pocket drives, but I blew up a couple of them by using the wrong power supply, and the others are at work. Hunt of the house eventually yields a pocket driving belonging to husband (who is amassing marital points at an unprecedented rate during this exercise) and transfer the video to my computer. But when I play it, the audio is out of sync with the video.
Now, although this is disappointing, I’m not sure whether it’s good news or bad news. The good news is that the file is clearly fine when played on either the camera or my husband’s PC. So the problem is with my PC and how it is interpreting the file. So I feel I have to get to grip with codecs again. The software has actually told me which codecs were used with the file, and I make a note of them. Googling the IDs leads me to a website that has oodles of codecs that you can download. A bit more Googling allows me to find out how to see which codecs are already installed on my machine. But now I have a quandary. It’s not clear to me that the codec download site is safe, and a bit more Googling confirms my worries. It seems that you can end up far worse than you started if you download a dodgy codec. So I have a new idea. I’ll try the Microsoft site and see what it says about codecs. What it says is possibly the least helpful advice I have ever seen. It suggests you search on the internet for the codecs you need, but it then says that it can be really, really dangerous to download codecs from the internet, and warns you against it.
Well, I think, maybe if I download an up-to-date version of Moviemaker, it might come with useful codecs. On to the Microsoft site. Yes, there’s a more recent version of Moviemaker, and I initiate the download process. But then it demands verification via Microsoft Genuine Advantage. This rings faint bells as something I decided not to sign up for, having read reviews that suggested it could slow up your machine. I think that maybe I should give it a try, but when I try to do so I ultimately get to a website that explains that the page isn’t working and Microsoft is aware of the problem.
I decide that, rather than wasting time on a fruitless hunt for a safe codec, I will shoot one more bit of footage. Once again, make-up, nice top, pearls. Part of me wonders whether there’s any point to this, and whether I should not instead adopt the Mary Beard approach of appearing au naturel. It definitely works for Mary, who is widely adored for her robust attitude to those who think she should have a make-over for TV. But I decide that I can’t now change tack, as it would really look weird if one bit of view had me all glammed up and the next one had the normal scruffy Bishop. The first two takes are fluffed, but the third is perfect. Except that when I try to stop the recording, the device is frozen. No buttons at all work, even the off switch. I’m starting to get emotional but have to try not to cry as it would just make my makeup run (another good reason for adopting the au naturel approach). The manual is singularly unhelpful - its advice on problems is restricted to occurrences such as having one’s finger in front of the viewfinder. Googling doesn’t help either. All my experiences seem unique to me - further evidence of the malign force. Only solution, I guess, is to remove the battery. That restores the camera to normal functioning, but the last, perfect, take is described as “file type unknown”.
Back upstairs for yet another session. Eventually manage a version that seems okay, which I download successfully. And which looks fine on husband’s laptop but out-of-sync on mine. Thankfully get back into tracksuit, remove makeup, and decide I will reward myself with a negroni and an episode of the Bridge.
If these videos do ever get onto the RALLI site, you may think that I look a bit stressed for someone who’s just doing a three-minute piece. But now you know the true story.
Sunday, 6 May 2012
One of the great things about blogging is that it allows for communication to proceed far more rapidly than would be possible through conventional academic publications. In previous posts I’ve made a plea for MRI researchers to share data so that claims about the neurobiology of conditions such as dyslexia and autism can be replicated. After my last blogpost, I was contacted by Mark Eckert from the Medical University of South Carolina, one of the pioneers of MRI studies of dyslexia (e.g. Eckert et al, 2005). He tells me that a data-sharing project on dyslexia is already underway and asked if I would be able to share this information with my followers. I am of course delighted to do so! Here is some background from Mark:
The structural neuroimaging literature on dyslexia and other complex disorders is filled with inconsistent results. Meta-analysis provides a mechanism for identifying results that are common across studies, but direct analysis of the same datasets provides greater power, methodological consistency, and new analysis opportunities that include taking advantage of the behavioral and neural heterogeneity that is often problematic in small samples. For those reasons, there is a growing interest in sharing data. Prospective multi-site studies are ideal because the same data collection and quality control procedures can be used across sites. These studies tend to be very expensive, however. Retrospective studies take advantage of existing datasets that are housed in dusty hard drives, but are limited by methodological inconsistencies across sites. A new NIH supported project, directed by Mark Eckert, uses dyslexia as a model to address the challenges facing retrospective multi-site studies. Methods are being developed in this project to address subject privacy, behavioral heterogeneity in dyslexia and control samples, missing data, and the underestimation of the variance in datasets when pooling data across different research sites. His research group is collecting existing neuroimaging datasets and aims to have more than 2000 pediatric and adult cases from reading disability studies. One long term goal of this project is to make available much of the data collected for this study so that scientists can ask new questions, apply new methods to the data, and develop new collaborations with other scientists who have complementary expertise and interests in reading disability. There are incentives for research groups to contribute data. For example, contributors will be included in a Dyslexia Data Consortium that will be included in the list of authors for manuscripts stemming from this project. If you are interested in learning more about the study and/or would like to contribute data, please contact Mark Eckert at dyslexia @ musc.edu.Eckert MA, Leonard CM, Wilke M, Eckert M, Richards T, Richards A, & Berninger V (2005). Anatomical signatures of dyslexia in children: unique information from manual and voxel based morphometry brain measures. Cortex; a journal devoted to the study of the nervous system and behavior, 41 (3), 304-15 PMID: 15871596
Wednesday, 2 May 2012
Specific language impairment (SLI) and dyslexia are related developmental disorders in which a child has difficulty learning to talk (SLI) or to read (dyslexia). Many children have both problems, although they can occur separately (Bishop & Snowling, 2004), and they are sometimes grouped together as ‘language learning impairments’. There's good evidence that genes are implicated in causing these conditions (Bishop, 2009).
Webster, R. I., Erdos, C., Evans, K., Majnemer, A., Saigal, G., Kehayia, E., . . . Shevell, M. I. (2008). Neurological and magnetic resonance Imaging findings in children with developmental language impairment. Journal of Child Neurology, 23(8), 870-877. doi: 10.1177/0883073808315620
A popular account maintains that the genes implicated in language learning impairments affect a very early process in the developing brain known as neuronal migration (Galaburda et al., 2006). It’s an attractive theory that has the potential to provide a link from genes to behaviour. However, when I looked at the evidence, I found myself not entirely convinced. Here I’ll briefly review research on this topic, explain my reservations, and conclude by proposing a study that needs doing. I’m not an expert in neuroanatomy or neuroimaging, so I’ll be interested to see if others think this proposal is sensible.
Abnormalities found in 1979 case report. Solid circles show ectopias/dysplasias, and shaded area shows micropolygyria (based on Galaburda et al, 1985) .
Over thirty years ago, Galaburda and Kemper published a post mortem study of the brain of a man with developmental dyslexia who died from an accidental fall at the age of 20 years. He’d had delayed language development, and was diagnosed with dyslexia in the first grade. His Stanford-Binet IQ of 105 was well in advance of his reading attainments. He developed epilepsy at 16 years of age. His brain showed areas of displaced neurons (ectopias) in the left cerebral hemisphere, especially around the left planum temporale. There was also an area of polymicrogyria, i.e. excessive number of small convolutions, giving a lumpy appearance to the cortex. This raised the possibility that we might find the origins of dyslexia not in the gross features of brain structure, but at the microscopic level, in the organisation of neurons. However, as the authors noted: “It is not possible to tell from a single case whether or not the anatomical findings have any causative relationship to the clinical findings – much less whether the malformation is responsible for the seizure disorder, the learning disability, both, or neither” (p. 99). They also noted that the kinds of neuroanatomical abnormality that they found in their patient were probably too rare to explain dyslexia in general, which has a prevalence of around 5-10% in the population.
A subsequent report added further evidence for a link to dyslexia (Galaburda et al, 1985). Similar abnormalities were found in three further post-mortem cases, and in none of these was epilepsy described, though one had delayed speech and one had “notable language difficulties”. Three additional cases, this time of female dyslexics, were reported by Humphreys et al (1990), but these were less compelling: the evidence for migrational abnormalities was less strong, and other pathologies could have been implicated.
There’s a general problem with the methodology of these studies, which is that they were not conducted blind. The cellular abnormalities that were described require an expert eye and clinical judgement, and you wouldn’t necessarily see them unless you were looking for them. Could they just be spurious findings? Galaburda and colleagues noted that similar anomalies are sometimes reported as incidental findings in unselected autopsy brains, and so a key question was whether the findings in dyslexic brains were really unusual. Accordingly, Kaufman and Galaburda (1989) analysed ten control brains using identical procedures to those used for dyslexic brains. They found abnormal cells in three control brains, but the anomalies were far less numerous than those seen in the dyslexic brains. This provides useful context, but ideally, we need a study where the neuroanatomist is given both dyslexic and control brains and asked to analyse them without knowing which was which, to avoid the perceptual and cognitive biases that can affect even the most scrupulous of observers.
The anomalies described by Galaburda and colleagues reflect disruption at an early stage of brain development, when neurons are being formed and organised into coherent structures. This website from Pasco Rakic has some nice animations showing how a brain is formed when neurons are first generated in the foetus. Neurons formed in the ventricular zone travel out to the surface of the cortex along radial glial fibres, gradually building up six distinct layers of the cortex from the inside out. Studies with rodents, and evidence from humans with developmental disorders, indicate that this process can be disrupted in a range of ways. In some people, a proportion of cells fail to migrate at all, and can be seen as clusters of abnormal cells around the ventricles. This condition, known as periventricular heterotopia, does not normally impair cognitive function but does cause epilepsy. In other cases, there is partial migration followed by arrest, leading to lissencephaly, typically associated with epilepsy and severe intellectual impairment(Guerrini& Parrini, 2010). In mice, a naturally-occurring genetic mutation leads to the phenotype of the reeler mouse, which has severe motor co-ordination problems linked to disorganisation of the usual laminar structure of the cortex, because the migrating neurons fail to penetrate to the surface of the brain. The cases studied by Galaburda and colleagues had a range of anomalies, described as ectopias, dysplasias, heterotopias, ‘brain warts’ and polymicrogyria, associated with disruption affecting different stages of neuronal migration and postmigrational development (Barkovich et al, 2012).
What makes this work exciting is a potential link to genetic studies of dyslexia. There are replicated associations of dyslexia with several genes, including DYX1X1, KIAA0319, DCDC2 and ROBO1. As Galaburda et al (2006) noted in their review, mutations of these genes have been linked to migrational anomalies in rodents. It looks, therefore, as though the route from brain to behaviour could be neatly explained by postulating a genetic influence on neuronal migration that leads to a brain that is not optimally connected.
Some puzzles, however, remain. First, the genetic variants associated with dyslexia are not mutations. They are common in the general population. Associations with dyslexia are found in studies with very large samples, but they are not very strong. For instance, one can deduce from the published data on the KIAA0319 locus that there is a low-risk version of the gene that is found in 39% of normal readers and 25% dyslexics, and a high-risk version that is found in 30% of normal readers and 35% dyslexics. If the dyslexic risk variant causes anomalies of neuronal migration, then we should see lots of people with those anomalies, many (most) of whom will not be dyslexic. Of course, it is all a matter of degree; it is possible that each risk variant has only minor effects on neuronal migration, and causes problems only if it occurs in conjunction with other genetic or environmental risks. Neuronal migration can be affected by environmental factors, such as toxins, nutrition, and disease or trauma affecting the brain. So the ubiquity of these risk alleles does not rule out a causal route via neuronal migration mechanisms, but it does make the story more complicated.
What if we look at the association between neuronal migration disorders and dyslexia from the other direction, i.e. assessing reading ability in individuals with known migrational abnormalities? Chang et al (2005) did this in people with periventricular nodular heterotopia - a disorder in which a proportion of neurons fail to migrate from the ventricular zone. Most of their participants had normal range IQ. On the Wide Range Achievement tests of reading and spelling, their mean scores were average or above-average. Many of them did, however, do poorly on the Nelson-Denny reading test and on this basis, the authors concluded they were dyslexic. But this test, which stresses speed, was designed for college students, not for the general population. The fact that most participants were older than college students, and all were on anti-epileptic medication, makes the claim of dyslexia in these people far from convincing. Minimally, this study should have included a comparison group to control for age, background and medication status.
A final issue is why migrational abnormalities haven’t been noted in MRI studies of dyslexia. In studies of children with specific language impairments, a Brazilian group has reported remarkably high rates of polymicrogyria (De Vasconcelos Hage et al, 2006). However, this does not seem to be a general explanation for SLI. My colleagues tell me there were no cases of this in people with SLI who participated in a recent MRI study that we published, and none was mentioned in a series reported by Webster etal (2008). MRI studies of dyslexia have been considerably more numerous, yet, as far as I can establish, none has mentioned migrational anomalies. Of course, many MRI studies focus on averaged data, which would mask individual variations. So, a key question is whether the failure to report migrational abnormalities in MRI studies is because (a) no-one was looking for them, (b) they are too subtle to see on regular MRI scan, or (c) they aren’t involved in most cases of language learning impairments.
I was intrigued by this question, so I looked for literature on detectability of neuronal migration anomalies on MRI scan. My impression is that these wouldn’t necessarily be detected unless you were looking for them, and if you were, detectability depends on the type and location of anomalies. Wagner et al (2011) devised an automated method of MRI analysis that was successful in picking up 82% of Type IIA cortical dysplasias and 92% of Type IIB, compared to 65% and 91% detected by an expert neuroradiologist. Periventricular nodular heterotopia seems a more obvious pathology that is routinely detected on MRI scan.
On this basis, I’d say there’s a study out there crying out to be done. There are plenty of reports of MRI scans comparing dyslexic vs control brains. We could revisit those scans using the automated methods developed by Wagner et al to test the hypothesis that the rate of neuromigrational anomalies is higher in the dyslexic vs control samples. It’s clear that MRI scans won’t pick up everything, and subtle anomalies may be missed. However, if the neuronal migration account of language learning impairments is correct, we should nevertheless expect to see a measureable difference in the rates of anomalies between cases of dyslexia/SLI vs. controls. And if genetic information is available as well, then a comparison could be done between those with and without risk variants.
Barkovich, A. J., Guerrini, R., Kuzniecky, R. I., Jackson, G. D., & Dobyns, W. B. (2012). A developmental and genetic classification for malformations of cortical development: update 2012. Brain, 135(5), 1348-1369. doi: 10.1093/brain/aws019
Bishop, D. V. M. (2009). Genes, cognition and communication: insights from neurodevelopmental disorders. The Year in Cognitive Neuroscience: Annals of the New York Academy of Sciences, 1156, 1-18.
Bishop, D. V. M., & Snowling, M. J. (2004). Developmental dyslexia and Specific Language Impairment: Same or different? Psychological Bulletin, 130, 858-886.
Chang, B. S., Ly, J., Appignani, B., Bodell, A., Apse, K. A., Ravenscroft, R. S., . . . Walsh, C. A. (2005). Reading impairment in the neuronal migration disorder of periventricular nodular heterotopia. Neurology, 64(5), 799-803.
De Vasconcelos Hage, S. R., Cendes, F., Montenegro, M. A., Abramides, D. V., Guimarães, C. A., & Guerreiro, M. M. (2006). Specific language impairment: linguistic and neurobiological aspects. Arquivos de Neuro-Psiquiatria, 64, 173-180.
Galaburda, A. M., & Kemper, T. (1979). Cytoarchitectonic abnormalities in developmental dyslexia. Annals of Neurology, 6, 94-100.
Galaburda, A. M., Sherman, G. F., Rosen, G. D., Aboitiz, F., & Geschwind, N. (1985). Developmental dyslexia: four consecutive cases with cortical anomalies. Annals of Neurology, 18, 222-233.
Galaburda, A. M., LoTurco, J. J., Ramus, F., Fitch, R. H., & Rosen, G. D. (2006). From genes to behavior in developmental dyslexia. Nature Neuroscience, 9, 1213-1217.
Guerrini, R., & Parrini, E. (2010). Neuronal migration disorders. Neurobiology of Disease, 38, 154-166.Wagner, J., Weber, B., Urbach, H., Elger, C., & Huppertz, H. (2011). Morphometric MRI analysis improves detection of focal cortical dysplasia type II Brain, 134 (10), 2844-2854 DOI: 10.1093/brain/awr204
Webster, R. I., Erdos, C., Evans, K., Majnemer, A., Saigal, G., Kehayia, E., . . . Shevell, M. I. (2008). Neurological and magnetic resonance Imaging findings in children with developmental language impairment. Journal of Child Neurology, 23(8), 870-877. doi: 10.1177/0883073808315620