The remediation effect of phonologically based dyslexia interventions in specific brain areas

The Remediation Effect of Phonologically Based Dyslexia

Interventions in Specific Brain Areas

Lara van Teunenbroek 10182586

Number of words abstract: 124 Number of words: 5214

Table of Contents

The Remediation Effect on Phonologically Based Dyslexia

Interventions in Specific Brain Areas 2

Which Brain Areas are involved in Dyslexia? 6

Which Reading Interventions Have an Effect on Specific Brain

Regions of the Reading Network? 9

Which Brain Areas Show Sensitivity to Effect Phonologically

Based Interventions for Children With Dyslexia? 12

Conclusion & Discussion 15

The Remediation Effect on Phonologically Based Dyslexia Interventions in Specific Brain Areas

This review aimed to better understand the remediation effect on phonologically based dyslexia interventions in specific brain areas. Lacking phonological awareness, a key

ingredient in acquiring reading skills, is proposed to be the main cause for reading impairment. Children with reading disabilities show differences in activation in the

parieto-temporal region, the inferior parietal lobe and the fusiform gyrus, the inferior region. After phonologically based interventions, children with dyslexia show more normalized activation

at the previously mentioned regions, related to more accurate and more fluent reading. However, some children remain non-responsive after receiving treatment. Contradictory

results emerge researching this topic. Mostly, posterior temporal regions show underactivation and frontal regions show greater activation after receiving treatment.

Differences in studies are usually found in superior temporal regions.

Dyslexia or reading disability is a specific reading and spellings disorder with a neurobiological basis, which is caused by cognitive processing deficits. People with dyslexia have difficulty with reading accuracy and fluency, despite having normal other cognitive abilities and despite regular education (Blomert, 2005). It is a relatively common diagnosis with prevalence rates varying between 3% and 10% of the population (Snowling, 2001).

As dyslexia is a well-studied disorder researchers are still debating its exact neurocognitive-underlying deficit. Most of the dyslexia theories suggest a phonological awareness deficit as the main deficit in developmental dyslexia. Phonological awareness or the ability to manipulate, analyze, and synthesize the sounds of a language is necessary in order to master the correspondence of sounds to letters and is therefore also necessary for acquiring reading skills (Noble & McCandliss, 2005). The phonological deficit suggests that dyslectic readers have difficulty manipulating phonemes, the smallest unit of sound that makes a difference in meaning and thus distinguishes words from one another. For example when the b in “bat” gets replaced by an h the new word is “hat”, and the meaning of the word has changed completely. This phonological impairment has been suggested to interfere with the establishment of phoneme-grapheme or letter-speech sound associations (Peterson & Pennington, 2012). This causes problems such as verbal short-term memory, poor phonological learning of new verbal information, word retrieval and rapid naming problems (Snowling, 2001).

However, the phonological awareness theory has not been fully accepted among all researchers. The theory lacks full support due to several signs. One of which is the bilateral

relation between fluent reading acquisition and phonological awareness. Meaning that phonological awareness can improve along with reading and is not necessarily a prerequisite. A more recent theory, which is based on the phonological theory, is the phonological integration deficit (Blomert, 2011). This theory claims that when letter-speech sound associations have been formed, it will take years of instruction and practice before the associations become fully automated. Blomert refers to the integration process of grapheme-phoneme associations to audiovisual objects as letter-speech sound binding. According to this theory the reading disfluency is primarily due to a not well-automatized letter-speech sound binding. Suggesting that the integration between letter-speech sounds might be necessary in order to develop phonological awareness. This cognitive impairment results in disfluent word recognition and thus provides a link to the behavioral manifestation of the disorder. That reading disability is caused by a deficit in letter-speech sound binding rather than phonological awareness is based on studies finding a multisensory deficit in young children in the first stages of reading acquisition (van Atteveldt, Formisano, Goebel, & Blomert, 2004). The phonological integration deficit is therefore not a consequence of years of bad reading.

Despite the converging evidence of the phonological deficit and the following phonological integration deficit theory other researchers have also tried finding an explanation for dyslexia. Alternative theories such as the visual attention theory and the double deficit theory have been thought of, but show substantially less support than the phonological theory (Peterson & Pennington, 2012). Since dyslexics also show problems in naming speed of visual objects, Bowers & Wolf (1999) proposed the double deficit theory. According tot this theory phonological awareness is a primary deficit in dyslexia, but naming speed problems represent a second core deficit. The second deficit is related to lower level processes such as visual attention that are relates to a rapid naming deficit. Combined these deficits cause a profound reading impairment. Vaessen, Gerretsen & Blomert (2009) explored this theory, but found that even though general processing speed was involved in speeded naming of visual objects, it did not explain the relationship between naming speed and reading speed. The visual attention span deficit theory has also been suggested to contribute to dyslexia independent of phonological impairment (Bosse, Tainturier, & Valdois, 2007). Nonetheless, there have limitations in studies done on this topic. For instance the use of an oral report task itself uses both rapid naming and phonological short-term memory, two elements dyslexics are known for having difficulty with (Peterson & Pennington, 2012).

Since phonological awareness cannot be perceived by the naked eye and cannot be derived from test scores or reaction times, neuroimaging techniques allow one to take a better

look at the underlying cognitive processes involved in reading (Blomert, 2005). Functional magnetic resonance imaging (fMRI) studies have looked at which regions are involved in reading and suggest a left lateralized ‘reading network’. This network includes three regions. The visual orthographic region is thought of as the initial visual processing area and feeds information into the visual word form area (VWFA), which is situated at the fusiform gyrus. This area is argued to be involved when processing shapes or images prior to association with phonology or semantics (Dehaene & Cohen, 2011). The remaining two areas involved whilst reading are part of the phonological system. The left dorsal posterior component or perisylvian region is mostly activated when reading non-existing words also known as pseudowords and is known to link orthography to phonology. The third region, the left anterior component, is associated with speech production and analyses the phonological components in words (Schlaggar & Mccandliss, 2007). Where fMRI studies are needed to show activated areas during reading, event related potentials (ERP) studies offer a better look at the time course of neural activity during reading.

There are a number of tasks that are typically used in neuroimaging studies. A task that is often performed in children is the phoneme identification task, in which one phoneme in a word has to be identified as it suits the cognitive ability of kindergartners (Torgesen, 1998). This task showed to be predictive in learning how to read as phonological awareness is a better predictor of teenage reading ability than kindergarten reading skill is (MacDonald & Cornwall, 1995). Another phonological awareness task is the visual rhyming task. Even though this task is thought of as an easy task, it provides an independent contribution to reading and is more important than reading syllables (Høien et al., 1995). On the other hand a relatively difficult task is the phoneme manipulation task. It requires children to add or delete phonemes in order to formulate new words (Vloedgraven & Verhoeven, 2007). The tasks performed when using neurological techniques are usually done before and after children received treatment.

As dyslexia is a common learning deficit in children, many different treatments have been developed for dyslexia. However not all treatments are effective and so it is essential to distinguish the effective treatments from the less- or non-effective treatments. Development & Child (2000) conducted a study in which five key elements included in treatments for dyslexia have been shown to be most helpful in improving reading. Components included were effective reading instructions are phonemic awareness, phonic skills, vocabulary, fluency, and reading comprehension. Phonemic awareness training consists of a systematic exploration of the articulation of phonemes, which integrates decoding and spelling instruction. Phonic skills

or the ability to comprehend, analyze, and manipulate letters are difficult for children with dyslexia. Children therefore learn to use mirrors and mouth pictures to reference their mouth position and movement while reading. Vocabulary is enhanced by reading texts and improving fluency is done by guiding and timing the children in reading decodable words. Last but not least an important element to work on is reading comprehension. Dyslexia treatments include comprehension monitoring, question generation, story structure, and summarizing.

Studies show convergent evidence in favor of the phonologic awareness theory. Educational policies have therefore been altered and generally accepted evidence based treatments try to tackle the phonological awareness deficit. Nonetheless, the underlying pathology of dyslexia remains uncertain. Neuroimaging techniques provide a tool to explore the neural basis of dyslexia. (Maisog, Einbinder, Flower, Turkeltaub, and Eden, 2008). For some children phonological based treatments positively alter the activation of key areas in the brain used for reading. However, it remains unclear why 2% to 6% of the dyslectic children undergoing treatment, remain non-responsive to these treatments (Torgesen, 2000). The present thesis aims to better understand the remediation effect of phonologically based dyslexia interventions in specific brain areas.

To better understand the remediation effect of dyslexic interventions, it is necessary to gain insight in the neurological changes following these treatments. To do so it is essential to know the key brain areas that are active while reading. Consequently, once these areas have been located it is of importance to see whether the phonological awareness tasks used in evidence based treatments have an effect on the key areas needed for reading. Furthermore, it is evident that not all children respond to phonological based interventions, it is therefore crucial to try and see whether there are differences in effect of phonological based interventions between children with dyslexia.

Which Brain Areas are involved in Dyslexia?

Most languages use alphabetic scripts with corresponding sounds to the visual symbols, or graphemes. To adequately use these letter-speech sound associations takes extensive practice and these associations need to become automatized to acquire fluency. When this process fails, reading disabilities will most often occur (Blomert, 2005). Insights to these processes and functional brain areas involved in reading can therefore help us gain understanding of abnormal literacy development.

Van Atteveldt, Formisano, Goebel, & Blomert (2004) used fMRI scans to explore the functional neuroanatomy of the integration process of letters and speech sounds. To do so participant listened and/or viewed a series of speech sounds and letters. Modality specific regions were found by using unimodal conditions whereas bimodal conditions were used in order to find integration regions. These integration areas were found in the superior temporal cortex. The modality specific regions were the inferior occipital-temporal cortex, which responded to visual stimuli but not to auditory stimuli, and the superior temporal cortex, which was activated when presenting speech sounds.

To further investigate the differences between dyslexics and non-dyslexics Cao and colleagues (2006) hypothesized that tasks that demanded more orthographic and phonological processing would show differences in brain activity between the two groups. Researchers examined this by creating a visual rhyming task where words were paired up and had one of four trials. A trial was either conflicting or non-conflicting. A conflicting trial consisted of similar orthography but different phonology (e.g., pint-mint) or similar phonology but different orthography (e.g., jazz-has), whereas a non-conflicted trial consisted of a similar orthography and phonology (e.g., gate-hate) or different orthography and phonology (e.g., press-list). Dyslexic children and non-dyslexic children but age-matched were compared by using fMRI techniques. The conflicted trials which were thought of as more difficult and would expect to result in greater behavioral and activation differences in the dyslexic group and the non-dyslexic group compared to the non-conflicting trials. As expected there was only significant differences in the conflicting trials. The left inferior frontal gyrus, the left inferior parietal lobule, the left inferior temporal gyrus/fusiform gyrus, and the left middle temporal gyrus were less activated in the children with dyslexia. The underactivation of the temporal and parietal regions suggests impairments in forming orthographic and phonological representations.

The previous study used a dyslexic group and an age matched normal reading control group. This showed that dyslexics presented less activation in the inferior parietal cortex, and a more activation in the inferior frontal gyrus. It is then of importance to ask whether these regions show a difference in activation, because of a slower development or if it is caused by reading ability. The next study therefore distinguished two control groups. The first control group was an age-matched control group and the second was a reading level matched control group younger than the dyslexic group but equivalent in reading performance. The group of dyslexics was first compared to the age matched non-dyslexic group followed by a comparison to the same reading level non-dyslexic group. The children had an average age of

14.4 years. This time MRI was used during a visual word rhyming task. Hoeft and colleagues (2007) found that there was a significantly greater activation in the left inferior frontal parieto-temporal and occitopal regions in the age-matched control group compared to the dyslexic group. However, when the dyslexics were compared to reading ability matched non-dyslexics, the hyperactivation was eliminated. So this hyperactivation in the frontal and occipital areas in the dyslexic group could be caused by their reading ability, whether the reading ability was related to normal development (younger age) or dyslexia. Furthermore, the study also found an under activation in three posterior brain regions in the dyslexic group compared to the age-matched non- dyslexic control group. These regions were, the left inferior parietal lobe and the left and right fusiform and lingual gyri. The hypoactivation in the left posterior cortex, remained after comparing the dyslexics to the younger but reading level matched individuals, but the group did not differ in the other regions.

The previous studies converge on the finding of underactivation in temporal, parietal, and occipito-temporal areas in dyslexia. These studies provide evidence for impairments in areas involved in integrating letters and speech sounds. In contrast it is not clear to what degree the phonological tasks activate the neural mechanisms involved when processing letter and speech sounds.

To investigate this question Blau et al. (2010) used a basic perceptual task to prevent group differences from appearing due to different tasks instead of different stimuli. There were to two groups that were being compared. The first group consisted of dyslexics while the other group consisted of non-impaired readers. The children in the study were age matched and selected at the earliest age known to be able to diagnose dyslexia. This is around the age of nine. The task consisted of detecting congruent letter-speech sound pairs using a standard test battery including a computerized reading test, a phoneme deletion task, a decoding task, and a letter-to-sound matching task. Results showed that neural integration of letter-speech sound pairs were impaired in the superior temporal sulcus, anterior superior temporal gyrus and fusiform gyrus in children with dyslexia compared to the non-dyslexics. This impairment is not caused by an inadequacy of letter-speech sound correspondences since they had normal results in offline behavioral tasks. Furthermore, taking into account the age these children were tested, the deficit in letter-speech sound integration is not the result of a lifetime of reading disabilities, but because of a characteristic in learning how to read.

Concluding, underactivated brain areas in aforementioned studies related to reading impairments are the occipito-temporal region including the fusiform gyrus and the tempo-parietal areas. The first two areas are involved in phonological storage when processing

phonemes, and for mapping graphemes to phonemes and the fusiform gyrus contains the visual word form area or the visual word-recognition pathway. The latter integrates audio and visual stimuli. These results are in line with the integration deficit theory suggesting that an inadequate development in these areas cause impairments in reading ability.

Blomert, 2011

Which Reading Interventions Have an Effect on Specific Brain Regions of the Reading Network?

When performing phonological tasks the posterior brain regions in dyslexics often show a reduced activation in comparison to normal reading children. Temple and other researchers suggest that with phonological training this underactivation can be reduced and reading speed and accurcay, the two components mostly impaired in dyslexics, should improve along with cortical plastic reorganization (Penolazzi, Spironelli, Vio, & Angrilli, 2010).

To show that phonological training is indeed more helpful in dyslexics and that the regions involved in phonological awareness have a difference in activation, Shaywitz et al. (2004) hypothesized that evidence-based, phonologically mediated reading intervention would improve reading fluency and the development of the occipito-temporal systems needed for reading. English dyslexics between the ages of 6 and 9 either followed an experimental intervention or a community intervention. The community intervention group received interventions commonly provided in school. This intervention included remedial reading, special education, modified classrooms, speech and language, and remedial supportive tutoring from one to four days in the week for 15 to 20 minutes. Dyslexics in the experimental

group received daily 50 minutes of individual tutoring that included a review of sound symbol associations, practice in phoneme analysis, timed reading, oral reading of stories, and dictation of words. A group of normal reading students formed the control group. After eight months of treatment the phonologically based intervention group and the control group showed increased activation in bilateral inferior gyri and left superior temporal and occipitotemporal regions, whereas the children in the community intervention group did not. This data suggest that the phonologically based intervention group and the control group developed reading systems at the same degree, and that phonological reading interventions thus facilitate underlying neurological systems needed for skilled reading.

The previous study focused on English or a non-transparent orthography, meaning that this language has less consistent mappings between letters and sounds (Peterson & Pennington, 2012). When languages have less consistent orthographies reading accuracy plays a more dominant role, whereas with consistent languages reading accuracy can be taught more quickly, and dyslexics differentiate themselves in their fluent reading from normal reading children (Peterson & Pennington, 2012). Therefore Penolazzi et al. (2010) investigated whether Italian speaking children with dyslexia, Italian being a more consistent orthography than English, would improve in reading fluency after a phonologically based treatment. The software program used in the treatment was based on timed passage reading by words, syllables or morphemes, and phonological awareness. The children had to use the program 10 minutes per day, 5 days a week for 6 months. Before and after the training EEG recordings were made when performing an orthographic task, a rhyming task and a semantic task. Results showed that dyslexic children shifted from an equally distributed activation in both hemispheres to left posterior site activation, similar to that found in normal readers. Children whose activation had changed the most into the left posterior site also showed the greatest reading speed improvement. After additional post-training sessions the reading speed of dyslexics ameliorated more than twice the annual spontaneous improvement shown by normal readers. Concluding that the significant improvement is not due to maturational factors, but due to the treatment given.

Richards et al. (2007) also researched the efficacy of phonological based interventions. However their study extended prior research by comparing phonologically based interventions to non-phonological interventions by using the same non-phonological treatment on dyslexics as well as on non-dyslexics to serve as a control group instead of using only well readers as a control group. This is necessary to assess whether the treatment effect is the same for both groups. Secondly, Richards and colleagues’ study added to the existing

research on this topic by comparing a phonological treatment to a non-phonological virtual reality control treatment. Specifically, the study conducted examined whether the frontal parietal en temporal regions previously associated with phonological processing showed significant differences in activation between dyslexics and non-dyslexics, and if these areas had a neurological change in response to treatment. They studied this using fMRI during the aural repeat task, where children had to orally repeat aurally presented pseudowords and the visual decode task, pronouncing visually presented pseudowords. There was also a control aural match task where children had to judge whether two aural pseudowords matched. The phonological training was given to the dyslexic children and the non-phonological training was both given to the dyslexics as well as the non-dyslexics children. Richardson et al. found that the left tempo-parietal region and post central gyrus decreased and normalized in activation for the phonologically treated group during the aural-repeat and aural-match task. Non-phonological treatment increased and normalized activation in dyslexics during the visual decode aural-match task. The non-phonological treatment also showed a significant difference in brain regions between the dyslexics and the non-dyslexics. The underactivated visual cortex in dyslexics was activated significantly during the visual-decode and aural-match tasks and the activation changed in the same direction as the activation showed in brain areas of well reading children. These findings suggest that non-phonological treatment also has an effect on dyslexics. Although significant results were found in the non-phonological treatment group, only the direction of change was similar to that of good readers, whereas the amount of activation in the phonological treatment group was as that of good readers. This study confirms that phonological based trainings do give better results than those of non-phonological training.

All of the previously mentioned studies with experimental manipulations have shown that phonological training and systematic instruction in letter-speech sound mapping have proven to be necessary to improve the reading ability of children with dyslexia in comparison to various control groups. Even though non-phonological training did show amelioration, only children who were treated with a phonologically based intervention came close to the reading ability of non-dyslexic children. This suggests that phonological training plays a causal role in the development of dyslexia, and has greatly influenced educational policies and the way remediation practices have developed (Noble & McCandliss, 2005).

Which Brain Areas Show Sensitivity to Phonologically Based Interventions for Children With Dyslexia?

The studies previously described have focused on phonological treatments and the effects or response to these treatments in neurological changes had on the brain and reading ability. After the extensive research conducted on dyslexia and phonological treatments, remediation centers have focused primarily on developing phonological treatments. The Dutch government for example implemented a strict diagnosing protocol, where once diagnosed, dyslexics only receive subsidy if they follow a certain phonological based treatment (Blomert, 2005). What these studies fail to mention is that not all children respond to current well-established phonological treatments (Torgesen, 2000). Researchers have suggested that children with a non-response to reading instruction are caused by neurological differences in children diagnosed with dyslexia (Noble & McCandliss, 2003; Shaywitz et al., 2004). To further explore this manifestation it is important to ask whether age is involved and therefore the maturation of brain regions. Furthermore, it is important to ask whether persistent impairments in brain functionalities between non-responders to treatment, responders to treatment, and well reading children would still exist after systematical reading interventions.

Although previous studies provide insights in the plasticity of the brain and its ability of functional reorganization after systematic reading instructions, the relative timing of neurophysiological activity has yet need to be clarified. The present study done by Simos et al. (2007) examined children at risk for dyslexia and who failed to respond to effective reading treatments. Children identified as at risk for dyslexia at the end of kindergarten, started treatment in the first grade. These children were randomly assigned to one of three treatments. The children either followed enhanced classroom reading instruction, or one of two daily small-group supplemental interventions for 40 minutes a day over 30 weeks. Children following one of the two supplemental interventions increased significantly in performance compared to children only receiving enhanced classroom reading instruction. However there were also children non-responsive to either treatment. These children followed another two-staged intervention. The first eight weeks was spent on phonological decoding skills for two hours each day and the following eight weeks on rapid word recognitions for one hour each day. Another group of non-impaired readers were also tested over a six-month period to check for confounding factors such as neurological maturation, and repeated exposure to stimuli. While performing a pseudowork reading task MEG scans were made. Results showed that children responding to the treatment showed significant increased

activity in the posterior superior temporal gyrus, and the supramarginal and angular gyri in the left hemisphere, and left tempo-parietal and frontal regions as well as non-responsive children. In contrast to the responders, non-impaired children did not show significant changes in these brain areas during multiple tests. Non-responders did however show changes brain activity in more frontal and right tempo-parietal regions of the brain. Simos et al. suggests this change in using alternate brain areas is due to provide an alternative strategy for mapping of sounds and printed stimuli when the natural pathway is impaired.

The non-responders to phonological treatment show neurological changes in the frontal and right hemispheric regions. It is yet unknown what the behavioral consequence is of these changes. To examine this difference in response to treatment and to observe what the functional variability is with children still finding reading difficulties in comparison to well reading children Odegard, Ring, Smith, Biggan, & Black (2008) studied the treatment effects of phonological interventions in responsive and non-responsive children with dyslexia. After a two-year treatment including 90 minutes a day for four days per week two groups were formed. The first group consisted of children between the ages of 10 and 14 and had average decoding and reading abilities. The second group consisted of children matched in age and in gender ratio to the previous group, but this time showing below average decoding and reading abilities. Within the second group Odegard & colleagues discriminated children who responded well to treatment and children who did not respond well to treatment. Response to treatment was defined by children demonstrating significant growth in phonological awareness and decoding ability, such that children were within the average range after treatment. FMRI techniques were used while children in the two groups were performing a phoneme-grapheme task. Results after treatment showed remediation of phonological awareness in all dyslexic children and that the ability of phonological skills does not discriminate responders from non-responders to phonological treatment. It was the continued inability to adequately decode real and pseudowords that identified these non-responders. This was also shown in the fMRI data where there continued to be less activation in the left inferior parietal lobe in non-responders, the area involved in linking orthographic to phonological representations of a language. Odegard et al. also found greater activation in the right inferior frontal lobe in comparison to responders and non-impaired children, but found no differences in groups in the superior temporal lobe. This conflicting evidence with the previous study that did find differences in activation in the superior temporal lobe between responders and non-responders might be explained by the amount of time that elapsed between the treatment and the obtainment of the data, and small sample size.

To further investigate the discrepancies in activation in the superior temporal lobe between Simos and Odegard’s paper, Davis et al. (2011) researched the functional correlates of responsiveness to evidence-based treatments in dyslexic children. Participants were on average 7,5 years old and they were all at risk for developing dyslexia. The children unresponsive to general classroom instruction were assigned to a small group, which received a reading intervention for 45 minutes 3 days per week for 17 weeks. This intervention included sight word reading, letter sound practice, decoding, and story reading fluency. Throughout the treatment growth of word identification fluency was measured using MRI data when performing a phoneme-grapheme task. Davis and colleagues focused specifically on the tempo-parietal regions of the brain since this area is involved in sound-letter associations. The largest group differences were found in the superior temporal gyrus between underactivation in the non-responsive group and normal activation in the responsive group. This area is argued to be involved in constructing the phonological representations of speech sounds. The lack of a pre-intervention MRI however prevents us from being able to conclude if the differences between treatment responders and non-responders are a cause or a result of children’s responsiveness to reading instruction.

Previous mentioned articles lack a plausible explanation for response to treatment. Non-responders still show below average decoding ability and phonological awareness after following phonological treatments. The recent fMRI studies only show non-conclusive differences in temporal and frontal regions between responders to treatment and non-responders. Nevertheless, it is apparent that these children show a persistent inability to read non-existing words.

Conclusion & Discussion

This review aimed to better understand the remediation effect on phonologically based dyslexia interventions in specific brain areas. Areas involved in reading comprise of the visual orthographic region the left dorsal posterior region, and the left anterior region. Together forming a reading network being able to decode and manipulate symbols known as letters and making letter-speech sound associations necessary for acquiring reading skills. Children with reading disabilities show differences in activation in the occipito-temporal region of the brain related to orthographic processing and that includes the fusiform gyrus, the tempo-parietal areas for audiovisual integration and the anterior regions such as the inferior frontal areas. After explicit instructions and evidence based reading interventions, more often than not, children with dyslexia show normalizing activation in previous mentioned regions enabling them to read more accurately and more fluently. Nonetheless, Torgesen (2000) reported a small namely a 2 to 6 percentage of children not responding to treatment. Non-responders being children who still show below average decoding ability and phonological awareness after following treatment. As little research has been conducted on the responsiveness to well-established treatments it was important to see the differences in neurological activation between these children with reading disabilities. The recent research that has been done on this topic provides us with inconsistent results. For most of the studies, posterior temporal regions show underactivation and frontal regions show greater activation. Differences in studies are usually found in superior temporal regions.

The differences found in results are probably due to the different tasks, different measurement techniques and small sample sizes. Simos measured neurological activity with MEGs, whereas Odegard and Davis measured neurological activity with fMRI scans. Also Simos used a pseudoword task, whereas Davis analyzed results from a phoneme-grapheme task. Even though these tasks are both related to phonological awareness the pseudoword task might be more dependent of one particular region in the reading network than the phoneme-grapheme task, causing different functional activity in the brain.

Age is another important factor to consider. First it is important to consider the age in which the children receive the treatment and if they are still non-responsive when they receive the treatment when they are young or when they are older and have already received several years of reading instruction. If the latter is the case, non-responsive children have surpassed the developmental stage critical to learning phonological awareness. Since the brain has such plasticity new neurological networks are formed when there are developmental impairments.

These new networks are the brain’s natural way to cope with its deficiency. Children that have surpassed the critical developmental stage in which they acquire the different cognitive skills required for reading will probably not be aided with present treatments. Therefore, neuroimaging studies might help to clarify and identify the critical developmental stages for learning these different cognitive skills. This will be useful to determine the best time to expose dyslexics or at risk dyslexics to different interventions.

The frontal and posterior temporal regions have shown to have a negatively different activation in dyslexics compared to non-dyslexics. Consequently, connectivity in the frontal and right temporal lobe might help us to determine whether these areas can be used to predict responsiveness to treatments. It is important to conduct longitudinal studies begun prior to the interventions to observe if these areas in the brain predict reading ability. Not only do these regions have to be studied prior to the intervention, but they also have to be studied long after the treatment to make sure that these areas still predict reading ability when they are adults. If this is indeed the case, future research could focus on new treatments that facilitate the activation of the frontal en right temporal region to reinforce the natural way of dealing with its deficit.

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