Developmental dyslexia is a neurological disorder that causes learning disability among 80% of the children. It is now well-established that dyslexia has a genetic origin however, the underlying the biological and the cognitive causes which guide the disease development is still debated (Frith, 2017). However, Saralegui et al. (2014) are of the opinion that the primary difficulty with respect to dyslexia reflects a deficiency in the communication skills or language system and visual complications. According to Handler and Fierson (2011) children with dyslexia suffers from learning disability. Handler and Fierson (2011) further highlighted that vision problems at times interfere with the process of reading. However, children with dyslexia or other children who are suffering from learning disability have nearly identical visual functions and ocular health status as reflected among the children without learning disability. Handler and Fierson (2011) highlighted that there is lack of proper scientific evidence to support this view that subtle eye or visual problems can cause or increase the severity of learning disability. Quercia, Feiss and Michel (2013) stated that development dyslexia affects at-least 10% of school-aged children however, a detailed etiology still remains unknown. One of the widely acknowledged theories in order to explain the etiology of dyslexia is consistent presence of phonological difficulties in combination with the inability to manipulate language sounds. Quercia, Feiss and Michel (2013) stated that anomalies of visual attention along with short visual attention are demonstrated in a number of cases. Spatial orientation is also affected among dyslexic who experiences a preference towards spatial attention to the right. This asymmetry cause veritable neglect of space on the left side. Advent of new explanatory theories further helps in the multimodal explanation of the visual inputs in dyslexia.
Several theories have been proposed in order to explain the learning disability and visual deficit associated with dyslexia. Some of these theories include auditory temporal processing deficit theory, Cerebellar theory and more recently the attention span of visual deficit theory and Magnocellular visual deficit theory of dyslexia. All these theories causes deficiencies in cognitive and visual processing leading to learning disability and speech problems (Saralegui et al., 2014). Rack (2017) proposed that the developmental dyslexia is a heterogeneous impairment, which results from cognitive disorders that are independent in nature. Here the majority of the individuals suffer from phonological deficit while other develop visual deficit. Pammer (2014) stated that children with learning disabilities or reading disorders have increased incidence of vision loss. Pammer (2014) highlighted that importance of vision therapy for reading and learning disabilities. However, there is no proven difference between readers with optimal and abnormal binocular function. Other studies conducted by Vagge, Cavanna, Traverso and Iester (2015) failed to highlight that increase in the rate of incidence of binocular vision problems among the children with reading ability. The abnormal tracking of eyes is also mistakenly indicated as the main underlying cause of reading difficulties among the dyslexic individuals (Vagge, Cavanna, Traverso & Iester, 2015). However, the research conducted by Saralegui et al. (2014) highlighted that the individuals with almost or complete inability to move their eyes have normal ability to read and write. From the ophthalmologic point of view it can be stated that individuals with dyslexia experience identical type of eye movements in the beginning. But, as dyslexics individuals experience normal sequential saccade tracking in the other areas of oculomotor functioning, it is assumed that abnormalities visualised in individuals with dyslexia during reading is an outcome and not the consequence of their reading disability (Saralegui et al., 2014). In other words it can be said that decoding or difficulties in comprehension in comparison to primary abnormality of the oculomotor control systems are reasons behind slow reading along with the higher duration about the fixations along with the backward saccades.
The recent studies conducted through the results of fMRI is able to support the hypothesis that promote visual magnocellular dysfunction is the consequence and the cause underlying the reading disabilities (Olulade, Napoliello & Eden, 2013). The aim of the research is to analyse the neural network while studying a group of children with dyslexia and compare the results with network obtained from the other group of children. The other group of children mainly encompass typical development complication, children with monocular vision which is secondary to ocular motility disorders and children who have impaired stereopsis and saccadic eye movements under binocular vision. The main hypothesis behind designing the aim of the research is there is difference in the neuronal imaging of the children ith dyslexia and other group of children. According to Peyrin et al. (2012) the difference in the brain scan fMRI results is extremely minute between individual with or without dyslexia. Thus the research will be conducted over a group of individuals in order to realiably detect the difference.
The main objective of the study is to analyse whether dyslexic readers have neuronal patterns which are similar to the group of children with ocular motility disorders. If difference is found in their neuronal reading networks, then ocular motility disorder will not be considered as a direct cause of dyslexia. The difference if elucidated in the neuronal imaging will further help to highlight the ocular movements as experienced by the patients with dyslexia. According to Vagge, Cavanna, Traverso and Iester (2015) detection or the identification of the ocular abnormality with the children with dyslexia will help in early detection along with implementation of the early intervention. Implementation of the early interventions with dyslexia will help the children to combat with their learning disabilities.
In order to conduct the study within the scope of the research, a comprehensive fMRI study will be conducted with the use of three different cognitive paradigms. This will help to explore the two principal domains of reading, phonological and orthographic parameter (Saralegui et al., 2014). The study will mainly emphasize over the two specific paradigms of lexical decision in order to elicit the overall activation of the phonological network. The study will also test the linguistic abilities of the two groups of children through the inclusion of specific paradigm for semantic categorization in order to activate the orthographic route. Under this orthographic route a subject has to generate a conceptual representation of two different cue words and find their respective relationships and compare the same with a selected group of words in order to determine if it belong under the same category. In relation to the fMRI imaging, it can be said that high resolution functional magnetic resonance imaging of the brain activity pattern that will be elicited by this set of test, reading-based paradigms will help to compare and contrast the underlying mechanism of dyslexia and its overall relation to the visual impairment. This will be beneficial consequences for the diagnosis and corresponding treatment of deficits of the overall reading system and reading retardation.
Participant population- From the department of Paediatric Neurology and Ophthalmology of a hospital, sixty children will be recruited along with that children from the nearby schools will be recruited for the study who will be considered as the control. The children will be recruited only after gaining a written informed consent from their parents. The selection criteria for the selection of the sixty children were as follows:
Inclusion criteria: The children had to belong to the age group of 9 to 12 years were all will be right-handed. The left handed children will not be included in the study in order to avoid the effects of laterality. The selected children should have English as their mother tongue in addition to having an IQ that is within the normal range, rather with average IQ. This will be considered in accordance to the Wechsler Intelligence Scale for Children—Fourth Edition, where the full scale will be IQ > 75 (Watkins & Smith, 2013). Additionally for the children belonging to the dyslexic group, there will be a requirement for the children to undergo a diagnosis of dyslexia however who do not have received children along with pycho-pedagogical support for literacy along with the children being assigned to the monocular vision group who will be considered as typical readers.
Exclusion criteria: Children having a past medical history of neurological disease or having symptoms like severe trauma along with impairment of the sensory-motor coordination and psychiatric illness will be excluded from the study. Additionally children who were subjected to continuous drug treatments along with experiencing social deprivation, inadequate schooling or who are intolerant to MRI scanning due to reasons of claustrophobia, loss of cooperation will be excluded. Additionally the participants with dyslexia and the control groups who had abnormalities in vision were excluded from the study. However exceptions were made in the case the participants having refractive error which is corrected with normal visual acuity or having abnormalities of mobility on clinical examination.
Data collection- Conduction of the experiments will be on the Philips Achieva 3.0-T MRI system having a 32-channel head coil. Anatomical acquisition will be carried out through the MR scanning protocol. For spatial corregistration along with anatomical reference, there will be implementation of structural MR scan. The BOLD functional images will be acquired through the three consecutive sequences.
There will be rendering of the surface of the location of the ROI that will be evaluated through the fMRI evaluation. For carrying out the definitive cognitive testing in the MR scanner, the participants of the study will be introduced to the cognitive tasks which will involve the functioning and displaying of the response systems in a computer system that is independent of the MR system (Paulesu, Danelli & Berlingeri, 2014). The experiment will involve lexical decision tasks where the first task will involve making the participants read two-syllable real words or the pseudowords. This will be followed by the second lexical/orthographic matching task involving the two sets of two-syllable pseudo words that will be displayed in a simultaneous manner. This will be followed by the third task that is the semantic categorization task. Here three words will be presented in a simultaneous manner, where two from the same semantic category will be placed at the top of the display however a third word will be shown at the bottom.
Data processing- In order to summarise the distributions in respect to the study variables and the demographic variables there will be use of the descriptive statistics. For the comparison between the socio-demographic and neuropsychological features there will be implementation of the non-parametric test like KW test, Wilcoxon rank sum test and the Pearson’s chi-square for categorical variables (Zhou, Xia, Bi & Shu, 2015).
Ethical considerations- Abiding by the code of Ethics of the World Medical Association the research will be performed along with the approval of the Clinical Research Ethics Committee of the concerned hospital were the experiment will be performed. An informed consent will be made to sign by the parents or the guardians of the participants who were recruited in the study. There is also a requirement for all the participants to be informed about the purposes and the protocols of the proposed study.
For this study, the results will be presented for each of the paradigm separately. In terms of the lexical decision, the group contrasts will show that in case of the dyslexic children there is a possibility of reduced activation in the area of the right Broca. The tests carried out will be able to show the significant difference between the left Broca’s area and right Broca’s area.
There will be six areas that will be studies in the ROI analysis of this task. In terms of the correlation of the score with respect to the three paradigms, the comparative analysis that will be performed will be able to show the areas of activation of the cortical with the three variables. This is thought to reflect in the best way the reading ability of the children. This will provide the accurate scores and the accurate clinical timing for the execution of the pseudo-word reading task that will be involved in the reading process evaluation. In regards to this, the fMRI analysis as proposed will depict the group differences in terms of the mean activation with respect to the three groups in the selected areas along with the pseudoword condition of reading of the task of lexical decision.
There will be eight areas that will be studies in the ROI analysis of this task. It is expected that there will be reduced activation in dyslexics in the left and right Broca’s areas in comparison to the other groups, however it will not be established until there is a statistically significant difference obtained. It is also expected that there will be significant differences for both right and left superior parietal lobes , where the left hemisphere will show an activation that is in significant difference to the DXRs with TDRs and for the right hemisphere there is significant differences will be found between DXRs and TDRs.
There will be eleven areas that will be studies in the ROI analysis of this task. In this case there will be an expectation of obtaining significant differences between groups that will be found for both left and right Broca’s area. Similarly it can be expected that for the other tests a same trend in the data will be found and for the activation in dyslexics there will be some difference in the TDR and the MVRs. In case of the left MTG, it was expected that there will be reduced activation in the TDR group as compared to others. However for that of the right MTG area, there is a tendency for high activation in the readers who are dyslexic in comparison to the other two groups.
For the Lexical Decision task, there will be a probability of obtaining large differences between the TDR and DXR groups. In the Lexical/orthographic matching task, there is probability of obtaining that the left Broca’s area will involve major differences between the DXR and TDR groups. In the Semantic Categorization task, the probability is that the right Broca’s area will show higher differences between the groups.
References
Frith, U. (2017). Beneath the surface of developmental dyslexia. In Surface dyslexia (pp. 301-330). Routledge. Retrieved from: https://www.taylorfrancis.com/books/e/9781351609784/chapters/10.4324%2F9781315108346-18
Handler, S. M., & Fierson, W. M. (2011). Joint technical report—Learning disabilities, dyslexia, and vision. Pediatrics, peds-2010. Retrieved from: https://pediatrics.aappublications.org/content/127/3/e818.short
Jednoróg, K., Gawron, N., Marchewka, A., Heim, S., & Grabowska, A. (2014). Cognitive subtypes of dyslexia are characterized by distinct patterns of grey matter volume. Brain Structure and Function, 219(5), 1697-1707. Retrieved from: https://link.springer.com/article/10.1007/s00429-013-0595-6
Krafnick, A. J., Flowers, D. L., Luetje, M. M., Napoliello, E. M., & Eden, G. F. (2014). An investigation into the origin of anatomical differences in dyslexia. Journal of Neuroscience, 34(3), 901-908. Retrieved from: https://doi.org/10.1523/JNEUROSCI.2092-13.2013
Olulade O. A., Napoliello E. M., & Eden G. F. (2013). Abnormal visual motion processing is not a cause of dyslexia. Neuron 79, 180–190. Doi: 10.1016/j.neuron.2013.05.002
Pammer, K. (2014). Temporal sampling in vision and the implications for dyslexia. Frontiers in human neuroscience, 7, 933. https://doi.org/10.3389/fnhum.2013.00933
Paulesu, E., Danelli, L., & Berlingeri, M. (2014). Reading the dyslexic brain: multiple dysfunctional routes revealed by a new meta-analysis of PET and fMRI activation studies. Frontiers in human neuroscience, 8, 830. Retrieved from: https://doi.org/10.3389/fnhum.2014.00830.
Peyrin, C., Lallier, M., Demonet, J. F., Pernet, C., Baciu, M., Le Bas, J. F., & Valdois, S. (2012). Neural dissociation of phonological and visual attention span disorders in developmental dyslexia: FMRI evidence from two case reports. Brain and language, 120(3), 381-394. https://doi.org/10.1016/j.bandl.2011.12.015
Quercia, P., Feiss, L., & Michel, C. (2013). Developmental dyslexia and vision. Clinical Ophthalmology (Auckland, NZ), 7, 869. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3656915/
Rack, J. P. (2017). Dyslexia: The phonological deficit hypothesis. In Dyslexia in children (pp. 5-37). Routledge.
Saralegui, I., Ontañón, J. M., Fernandez-Ruanova, B., Garcia-Zapirain, B., Basterra, A., & Sanz-Arigita, E. J. (2014). Reading networks in children with dyslexia compared to children with ocular motility disturbances revealed by fMRI. Frontiers in human neuroscience, 8, 936. doi: [10.3389/fnhum.2014.00936]
Vagge, A., Cavanna, M., Traverso, C. E., & Iester, M. (2015). Evaluation of ocular movements in patients with dyslexia. Annals of dyslexia, 65(1), 24-32. https://doi.org/10.1007/s11881-015-0098-7
Watkins, M. W., & Smith, L. G. (2013). Long-term stability of the Wechsler Intelligence Scale for Children—Fourth Edition. Psychological Assessment, 25(2), 477. Retrieved from: https://psycnet.apa.org/buy/2013-04443-001
Zhou, W., Xia, Z., Bi, Y., & Shu, H. (2015). Altered connectivity of the dorsal and ventral visual regions in dyslexic children: a resting-state fMRI study. Frontiers in human neuroscience, 9, 495. Retrieved from: https://doi.org/10.3389/fnhum.2015.00495
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