Dyslexia: insight into the mind via functional magnetic resonance images (fMRI) by Scott Block date: 21st of March 2008 Introduction: Dyslexia is a disability which can hinder the learning of the written portion of a language, particularly in reading and spelling. It does not result from poor vision, hearing, or lack of proper reading instruction. The individuals who are dyslexic vary in intelligence level from average to highly gifted, and in other words, what they are able write is not a true reflection of what they are capable of expressing through verbal means. “It is now well established that dyslexia is a neurological disorder with a genetic origin, which is currently being investigated[12].” In early stages of life, it is strongly recommended to give aid in teaching that individual, and the use of alternative remedial education is recommended. Parental involvement in all written aspects of educational life will be needed for many years. As a dyslexic individual begins to mature they start to develop tools to help them get through what is required of them to function well in society. Many dyslexic individuals, as adults, show a very strong work ethic and tend to obtain successful careers in the areas that they are gifted in. The strong work ethic comes from the years of having to put in more effort beyond what is normally required of most students their same age. Also due to these struggles with the written language, a very tight bond will develop between the dyslexic individual and who ever spends the most time with them trying to help them acquire the skills and tools needed. Due to different severities of dyslexia, some individuals will never be able to successfully express themselves in written form at their level of intelligence without the aid of tools, but no matter the severity of the case, there is no cure. Thankfully, in this day and age it is easier for people to use alternative methods to write down what they are thinking; for example, speak-to-write computer programs, text readers, and many more computer based tools. Outside the electronic realm, individuals with dyslexia have to rely on the kindness of others to help them get by. Motivation: To gain an understanding of some of the theories as to the possible cause/causes of dyslexia and the research behind those ideas. As human beings, there is always a constant curiousness of the world about us and about ourselves as individuals. To break the 3rd person barrier, I wish to know more about dyslexia, as I'm an individual that has it. I'm quite curious to know more about what goes on in the brains, that researchers have studied, of dyslexic people verses a normal control group of people through functional magnetic resonance images (fMRI). Problem statement: So typically, physically on the outside most people with dyslexia seem to be in the norm, so what are some of the trends of activity seen in the brain? Are there noticeable differences in brain “performance,” in reading and spelling of dyslexic test subjects verses control groups? If so, does the severity of dyslexia reflect in these differences? Does the brain “performance,” change with age? Do the control group and dyslexic group brains' “performances,” start to look similar the older you get? When a dyslexic person develops the use of tools, does the brain reflect this? Are there parts of the mind a dyslexic person will develop more, as in compensation? 1

Approach: Focus on the research that studies dyslexic people verses a control group via fMRI. Read what each researcher was testing for, how they were doing it, what their results where, and their conclusions. Some of the possible theories that will be focused on will be the phonological hypothesis, rapid auditory processing theory, visual theory, cerebellar theory, and magnocellular theory[1]. A little back ground information will be given on all the theories listed, but greater detailed information will be given on research focused towards the phonological hypothesis. This is due in part to past proven phonologically based intervention experiments and experiences that have help improve individuals' underlying understanding of their written language enough to successfully help that individual develop the tools they needed to get by. Results: A brief discussion of these experiments precedes their results. So typically, physically on the outside most people with dyslexia seem to be in the norm, so what are some of the trends of activity seen in the brain? Dyslexic individuals when performing phonological tasks have weaker responses in several regions of the brain. Continue to read to gain more information. Are there noticeable differences in brain “performance,” in reading and spelling of dyslexic test subjects verses control groups? If so, does the severity of dyslexia reflect in these differences? No information was added to this paper on that, more research is needed into this inquiry. Does the brain “performance,” change with age? Do the control group and dyslexic group brains' “performances,” start to look similar the older you get? When a dyslexic person develops the use of tools, does the brain reflect this? Are there parts of the mind a dyslexic person will develop more, as in compensation? Not enough information was found to give a definitive answer. Conclusions: The conclusion from the Yale University School of Medicine in association with Best Associates out of Dallas, Texas research groups from these long studies over many years was that “remedial educational intervention is critical to successful outcomes in children with reading disabilities and that the use of an evidence-based reading intervention facilitates the development of those fast-pace neural systems that underlie skilled reading[8].” Their finding suggest that educating children that are struggling with reading, dyslexic or not, through a “phonologically based reading intervention,” helps develop the skills, or tools, to become successful readers. What ever may cause dyslexia is still highly debated. Some features show up in subgroups of individuals with dyslexia more prevalently, such as lack of motor control, difficulties with deciphering letters, the poor ability in frequency discrimination, just to name a few, but no matter what theory is looked at, it boils down to dyslexia causes reading difficulties and hinders that individual in some societal ways. All this shows is that a lot of the things with the mind are so interconnected that there is most likely not just one root cause of dyslexia. Key words: dyslexic, dyslexia, functional magnetic resonance imaging (fMRI) 2

Functional magnetic resonance imaging (fMRI): The fMRI technique measures the blood flow overtime (hemodynamic response) [3]. This method of measurement is usually used to look at the blood flow change over time durations of seconds to minutes in the brain[2]. The underlying theory behind using fMRI is that where there is neural activity, blood will flow there, but there is a delay in how fast the blood can get to those areas of the brain. The blood will flow to the areas of neural activity approximately 1-5 seconds after that area of the brain has been used. After which the blood's hemodynamic response will rise “to a peak over 4-5 seconds, before fallingIllustration 1: Brodmann area, (Top) Sagittal view, (Bottom) Mid-sagittal back to baseline (and typicallyview[10] undershooting slightly)[3].” Functional MRI uses the same technology as MRI just applied for dynamic processes. Before delving into research pertaining to dyslexic minds a brief overview of how an MRI machine generates images is needed. Every atom has a spin; it's axes of spin will appear to be like a magnet with a north and south pole. In a MRI machine, there is a large magnetic field generated which will cause all the nuclei in the object to line up with the field with the north pole of each atom pointing to the south pole of the main magnetic field. Then a radio frequency (RF) pulse is broadcast towards the object causing only the atoms that resonate at that frequency to tilt with respect to the main magnetic field. Once the pulse has stopped, 3

the atoms will return to being parallel with the main magnetic field, “and the time that this takes is called the T2 relaxation time.” Each tissue, material, has a different T2 relaxation time. “Over time, the average angle at which the nuclei's spin axes deviate from the z direction,” defined as the main magnetic field direction, “returns to its normal low value,” is know as the T1 relaxation time (0.2 to 2 sec). As the nuclei return to being allied in the main magnetic field, each one of them becomes a miniature radio transmitter that gives “out a characteristic pulse that changes over time, depending on the local microenvironment surrounding the proton.” These radio transmissions are used to generate the MRI images[2][4]. MRI machines are able to obtain very sharp and clear images, but require the subject to be still for a considerable amount of time. The subject is also required to be still for a long time with fMRI machines, but for another reason. A MRI machine has a longer exposer time; this is the reason behind the ability to obtain sharp and clear images. Which won't help if your trying to study neural activity. MRI is noninvasive way to look at the brain tomography like (CT) scans and positron emission tomography (PET) scans, except the individual is not exposed to radiation[3][5][6]. Functional MRI can obtain spatial resolution in the region of 3-6 millimeters, but has relatively poor temporal resolution on the order of seconds[3]. The functional MRI is trying to obtain dynamic images of the brain and thus sacrifices image quality for speed (complete brain slice in 20ms in the year 1994)[2][7]. Thus, to obtain better image quality, a larger magnet or different image techniques are used. Since the temporal resolution is on the order of seconds, minimizing the movement from subject is very crucial. “Generally motion in excess of 3 millimeter will result in unusable data[3].” Echo-planar imaging (EPI): EPI technique is using an unique MRI technique that collects an image from “a single free induction decay signal (FID) in about 40 to 100 ms[13].” The capture time in this methodology is much shorter then the time seen in a hemodynamic response, and so this is a good technique to use to look at the dynamic aspects of the brain related to blood flow. The rapid auditory processing theory: This is an alternative to the phonological theory; it states that the phonological theory “is secondary to a more basic auditory deficit[12].” The rapid auditory processing theory basically states that dyslexic individuals have demonstrated the difficulty in perceiving “short or rapidly varying sounds (frequency discrimination[12])[1],” and because of this would have difficulties with phonemes, the smallest unit of sound that has meaning in a language. If an individual has difficulties with relating the smallest units of sounds to their written version, then reading difficulties would ensue. The visual theory: The visual theory does not disregard the phonological deficit; it just stresses that visual problems contribute to reading problems in some people with dyslexia. “The theory postulates that the magnocellular pathway is selectively disrupted in certain dyslexic individuals, leading to deficiencies in visual processing[12].” The Cerebellar Theory: The cerebellum has a large part “in motor control and therefore in speech articulation.” The cerebellar theory basically states that a person with dyslexia has a “mildly dysfunctional,” cerebellum and because of this “a number of cognitive difficulties ensue[12].”

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The Magnocellular theory: This theory is just rapid auditory processing, visual, cerebellar, and phonological theories all rolled into one[12]. Phonological hypothesis: A large number of studies point to dyslexia being a disorder within the “language system and more specifically within a particular subcomponent of that system, phonological processing[8].” Phonological processing is how your brain relates basic individual sounds that make up words (phonemes), identifies those individual units, and sequences those units to create words by which the society of that individual deems acceptable (correct spelling, orthography)[8][9]. The phonological hypothesis is that spoken language is natural and inherent, were as reading must be taught to the individual[8]. If there is a problem with the retrieval or storage “of speech sounds (phonemes),” then any thing related to the alphabet represented by these sounds will be effected for that individual. Dyslexic individuals also tend to have “poor verbal short-term memory and slow automatic naming,” which this observation “points to a more basic phonological deficit[12].” Yale University School of Medicine in association with Best Associates out of Dallas, Texas has done several studies of children and adults with reading difficulties, in particular dyslexia, over the years via fMRI and other brain imaging techniques. Their focus of research has brought them to the conclusion that dyslexia is a result of problems with the individual's ability to process phonologically. The first studied reviewed was conducted in 1998 on 61 right-handed adult participants; 29 of which were dyslexic readers (14 men, 15 women, ages 16 to 54) and 32 were non-impaired readers (16 men, 16 women, ages 18 to 63). They had the adults try to rhyme made up words. Echo-planar imaging technique was used to account for the differences in hemodynamic responses of each individual. “Echo-planar imaging can provide images at a rate fast enough to capture the time course of the hemodynamic response to neural activation,” by acquiring complete images in less then a second[8]. The results of the Yale and Best study was “significant differences in brain activation patterns between,” dyslexic and non-impaired readers when given tasks that put greater demand on that individual's ability to analyze phonologically. During the non-word rhyming they “found a disruption in a posterior region involving the superior temporal gyrus and angular gyrus with a concomitant (occurring with) increase in activation in the inferior frontal gyrus anteriorly[8].” The superior temporal gyrus is Brodmann marker number 22, angular gyrus is marker 39, and inferior frontal gyrus anteriorly is markers 44 and 45 (located in the pink, green, and yellow areas respectively of the brain diagram on page 3)[10][11]. This was a study done on adults, so the biggest concern is that these findings “may represent the consequences of a lifetime of poor reading,” and so they pursued the avenue of researching children in addition to adults to gain an understanding of how dyslexia develops during the acquisition of the ability to read and write[8]. Another study undertaken by the same group in 2002 examined 144 right-hand children; 70 were dyslexic readers (49 boys, 21 girls, ages 7 to 18, mean 13.3) and 74 were non-impaired readers (43 boys, 31 girls, ages 7 to 17, mean 10.9). The children in this study were asked to read pseudo and real words. The results of this study did find significant differences in the patterns of brain activation seen between dyslexic individuals and non-impaired readers. The children that were considered nonimpaired show a significantly more activity in contrast to the dyslexic children in the following left hemisphere areas of the brain “the superior temporal, parietal-temporal, and middle temporal-middle occipital gyri (respectively the marker 22 in pink region, 40 and 43 in the green area, 21 in pink, and some where in the middle of the blue region[10][11])[8].” The non-impaired children also showed 5

greater activation in the following right hemisphere areas of the brain the “anterior site around the inferior frontal gyrus and two posterior sites, one in the parietal-temporal region, the other in the occipital-temporal region (respectively markers 44 and 45 in the yellow region, around markers 40 and 43 in the green area, and region 19 in the blue area[10][11])[8].” The group from Yale and Best had an earlier experiment in 1994 geared to focus on children in reading intervention programs that met the “criteria for reading disability,” and had “received a variety,” of commonly provided school interventions. The research group created an experimental intervention group that provided second and third graders that were poor readers with 50 minutes of daily individual tutoring. The experimental intervention group was focusing the children on the “alphabetic principles (how letter and combinations of letters represent the small segment of speech known as phonemes).” During each session, the children were allowed to apply what they had been taught (to help reinforce it in their minds). For the community and experimental test subject groups, the children had to come from schools that didn't have any “specific, systematic, explicit phonologically based interventions,” or something of similar methodology to that used in the intervention programs that were being used for this experiment. Each of the children were imaged at three points in the experiment (before, right after, and 1 year after the end of the intervention). The results of this study saw an improvement in “reading accuracy, reading fluency, and reading comprehension,” in the experimental interventions group. The community and experimental intervention groups both showed “increased activation in left hemisphere regions including the inferior frontal gyrus and the posterior aspect of the middle temporal gyrus (respectively 44 and 45 in yellow, and 21 in pink[10][11])[8].” The major flaw with the phonological hypothesis: To gain an greater understanding of the phonological hypothesis, both the strong and week points of the argument must be presented. “The major weakness of the phonological theory is its inability to explain the occurrence of sensory and motor disorders in dyslexic individuals[12].” The supporters of the phonological hypothesis argue that dyslexia, at its root, is a reading disability and other disorders “co-occurrence,” don't have “a causal role in the aetiology of reading impairment[12][14].” Summary: The use of fMRI has shown a weakness in brain response of individuals with dyslexia under certain tasks. The research presented in the paper does not give any clue as to the origin or the cause of dyslexia, just some of the patterns noticed in the brain under certain stimuli. The research presented only has shown that individuals with dyslexia need to have additional written language intervention that is geared towards learning the relationship between sounds and their written equivalent at a relatively younger age. References: 1. Wikipedia, the free encyclopedia. 31st of January, 2008. 2.

Neurosciences on the Internet. 1994-2006 by Nei A. Busis, M.D.

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Wikipedia, the free encyclopedia. 26th of February, 2008. 6

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Horowitz, A. L. (1995). MRI Physics for Radiologists: A Visual Approach (3rd ed.). New York: Springer-Verlag.

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Wikipedia, the free encyclopedia. 25th of February 2008.

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Wikipedia, the free encyclopedia. 3rd of March 2008.

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Cohen, M. S., Bookheimer, S. Y. (1994). Localization of brain function using magnetic resonance imaging. Techniques in Neuroscience, 17(7):268-277.

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Bennett A. Shaywitz, G. Reid Lyon, and Sally E. Shaywitz (2006). The Role of Functional Magnetic Resonance Imaging in Understanding Reading and Dyslexi. Developmental Neuropsychology, 30(1):613-632.

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The Cognitive Aptitude Assessment Software. 3rd of March 2008.

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University of Michigan, Brodmann Area. 3rd of March 2008.

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Wikipedia, the free encyclopedia. 3rd of Febuary 2008.

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Franck Famus, Stuart Rosen, Steven C. Dakin, Brian L. Day, Juan M. Castellote, Sarah White, and Uta Frith (2003). Theories of developmental dyslexia: insights from a multiple case study of dyslexic adults. ©Guarantors of Brain, Brain:841-865

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Indian Academy of Sciences, acknowledgment to Dr. S. Naruse, Kyoto University 20th of March 2008.

14.

Snowling MJ. Dyslexia. 2nd ed. Oxford: Blackwell; 2000

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