How does dyslexia affect the brain

Let us not have to tread that course all over again. In other words, to claim that something is wrong, we must find evidence that it is not only atypical i.

We contend that this is very unlikely to be the case in dyslexia, not only because of the continuity with the rest of the reading skills distribution recall the arbitrary cutoff!

That is, demonstrating frank brain dysfunction in dyslexia is very unlikely because the majority of people with difficulties learning to read are in fact perfectly normal and have no other major difficulties in their lives beyond written language.

They speak fine, they walk fine, they socialize fine, they work and have families and are fine members of our society. This is not to deny that other systematic group differences may be associated with dyslexia, related, for example to speech and language development [ 72 ], psychophysical performance see discussion in [ 73 , 74 ] , or even various indices of neural function with typically much weaker associations; e.

Such differences, however scientifically informative, are far from diagnostic, as they invariably concern a minority of persons with reading difficulty and there is great overlap in performance between those with and without reading difficulty even when the groups are well separated on measures of reading skill.

Therefore, such associated group differences do not in any way constitute evidence for impairment beyond written language, even if they attest to on average somewhat lower performance in other domains, which may or may not be related to some aspects of some reading difficulties. Finally, all such findings are merely correlational and are probably most parsimoniously interpreted as reflecting common-cause situations in neural developmental trajectories or other etiological factors [ 77 ] rather than as directly related to the reading difficulties [ 73 ].

Put into perspective, calling dyslexics neurodevelopmentally disordered, and diagnosing them with disrupted neural development, amounts to calling neurodevelopmentally disordered any group that performs beyond some arbitrary cutoff on any skill.

This includes, for example, little Johnny and all poor singers, the clumsy children who are poor in sport or dance, and all those who perform at some low percentile in driving, chess, or speed dating. Given that most of us have found it overly challenging to acquire at least some of the skills we have encountered in our lives, and would probably have trouble with many other skills we have yet to encounter, a consistent application of the criteria used for dyslexia across domains would literally imply that we all suffer from some kind of neurodevelopmental disorder.

We hope we are not alone in finding this prospect untenable. The fact that modern society values literacy over singing, chess, or sense of direction does not make it a stronger candidate for a diagnosis of a disorder. Moreover, consistent application of the extreme-performance criterion would also include, for exactly the same reasons, all those who are at the top percentiles in reading, math, singing, sport, dancing, etc.

All that remains is to undertake the brain studies necessary for demonstrating the certain-to-exist differences. To sum up, there is at the moment no evidence to suggest that difficulty in learning to read words accurately and fluently is associated with anything having gone wrong in brain development.

This is in spite of the fact that dyslexia must be viewed as an expression of brain structure and function; that is, individual differences in normal brain development account for individual differences in the facility with which written language skills are acquired and expressed and in the levels of performance that are reached in given environments, with a given content and amount of instruction and experience. On the other hand, the low reading performance in dyslexia is not a symptom of some brain disorder, or even of disrupted neural development, but just the outcome of normal developmental trajectories that happen to be less efficient in acquiring and expressing written language skills, in the context of rampant, ubiquitous individual differences.

This view does not in any way imply that brain differences are genetically or otherwise predetermined. Simply put, brains are no more predetermined than the complex cognitive skills and psychological states they constitute are. As we have previously noted [ 15 ], we submit to the contemporary view that to understand reading difficulties it is necessary to study them in their proper multi-factorial context [ 77 , 78 ] under a neurodevelopmental perspective [ 79 , 80 ]; see also [ 49 , 81 ] , taking into account multiple factors that can affect the final outcome, in complex patterns of interaction, across levels of description, causal networks, and generations.

In particular, let us keep in mind that dyslexia is not a qualitatively distinct entity but just the low end of the word reading skill distribution, in continuity with the rest of the distribution, and with an arbitrary cutoff that essentially defines its prevalence on this behaviorally defined continuum.

The difficulties in learning to read are naturally accompanied by differences in the average patterns of activation, connectivity, or structural properties in the brains, as they must, given that no behavioral differences can arise in the absence of neural differences.

However, there is no evidence demonstrating that one end of a purported neural continuum, presumably reflecting the behavioral continuum, represents outcomes of developmental failure.

In saying this we do not wish to imply that specific lesions, or frank neurodevelopmental disorders, cannot lead to reading behaviors that meet any given diagnostic criteria for dyslexia; they clearly do. However, for most individuals with difficulty learning to read there will be no identifiable anatomical or functional markers of dyslexia in their brains to set them apart from those with no reading problems.

The critical issue is that the search for a single or double or triple cause for a behaviorally defined disorder, at any level of analysis, is misguided in its focus and counterproductive in its implications for interventions.

As compartmentalized approaches are gradually giving way to multifactorial developmental models and the focus moves on to understanding individual trajectories [ 15 ], we submit that it is time to replace the expectation of some sort of brain defect with an appreciation of individual variability in normal neural development and its multi-faceted consequences across skill domains.

We have outlined above the type of research findings that would be necessary in order to establish whether any actual anomalies are in fact involved in the causal pathways to dyslexia. Although we find it unlikely that they are, this is ultimately an empirical question that should be resolved by further studies, appropriately designed. We cannot prove that dyslexia is not a neurodevelopmental disorder, and this is not what we have tried to do in this contribution.

Instead, we have explained why none of the available kinds of evidence is relevant for deciding whether dyslexia is a neurodevelopmental disorder or not, and that it is at best premature to have implicitly decided that it is.

We have criticized the widespread conflation of two very different issues, namely the relational descriptive claim that groups differ in their average values on some measures brain-related or not and the normative claim that one group is composed of brains that have failed to develop properly. The former claim is well supported by available evidence but is irrelevant to the issue in question, whereas the latter claim requires mapping of individual differences, appropriate delineation criteria, and independent demonstration of dysfunction, none of which have been forthcoming.

Therefore, we believe that the field has been too hasty in embracing a position that is not supported by evidence. The need for interventions to remediate poor reading does not arise from the putative brain defects but from the poor reading itself, in the context of the modern literate society. Accordingly, recognizing that dyslexia does not constitute developmental failure, but is just an expression of normal individual differences, should have no practical implications for the special provisions that are needed to ensure universal literacy.

By analogy, little Johnny needs a lot of extra support, singing lessons, and probably special parts in the choir, if he is ever to become an adequately functional member in the family activities.

This is equally true whether or not he is told he has an unidentified brain defect. Dyslexia is not some pre-existing brain fault, distinct from normality, which hinders learning to read. Treating difficulty learning to read as some sort of neural disorder, akin to brain damage, is as offensive to the people who struggle with reading as it is misleading for the researchers who try to understand it and for the clinicians and educators who encounter it in their daily practice and will mistakenly come to associate it with pervasively disabling conditions with identifiable pathology and substantially poorer prospects.

National Center for Biotechnology Information , U. Journal List Brain Sci v. Brain Sci. Published online Apr 5. Author information Article notes Copyright and License information Disclaimer. Received Jan 15; Accepted Apr 4. This article has been cited by other articles in PMC. Keywords: dyslexia, reading difficulty, brain, neurodevelopmental disorder, neurological disorder, neuroimaging, fMRI.

Introduction Little Johnny was in distress. What Is Dyslexia? Brain Anatomy and Structure in Dyslexia There is a bit of—old but famous—evidence consistent with the idea that there is something wrong in the brain of some persons who have persistent unexpected difficulty in learning to read.

Functional Neuroimaging of Dyslexia What about functional markers? Open in a separate window. Figure 1. What Do Brain Differences Imply? What Can Group Differences Show? Where Does that Leave Us with Dyslexia?

Author Contributions A. Conflicts of Interest The authors declare no conflict of interest. References 1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. Bishop D. Which neurodevelopmental disorders get researched and why? Neurodevelopmental disorders: Conceptual issues. In: Rutter M. Blackwell; Oxford, UK: Neurodevelopmental disorders. Wiley Interdiscip.

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Critchley M. The Dyslexic Child. Heinemann Medical; London, UK: Snowling M. British Dyslexia Association Definitions. International Dyslexia Association Definition of Dyslexia. Parrila R. Dyslexia and word reading problems. In: Cain K. Theories of Reading Development. John Benjamins; Amsterdam, The Netherlands: Kudo M.

Reading disabilities in children: A selective meta-analysis of the cognitive literature. Landerl K. Predictors of developmental dyslexia in European orthographies with varying complexity. Child Psychol. Phonological skills and their role in learning to read: A meta-analytic review. Therefore, understanding the signs of dyslexia and receiving early diagnosis is crucial in managing this disorder.

These signs include: reading below the expected level, difficulty processing what one hears, and spending an unusual amount of time completing reading or spelling tasks. Fortunately, those with dyslexia can manage this disorder and still thrive in school by adopting an individualized plan and receiving external support from teachers.

Here are several signs of dyslexia: Reading well below the expected age level Problems processing and understanding what he or she hears Difficulty finding the right word or forming answers to questions Problems remembering the sequence of words and letters Difficulty seeing and occasionally hearing similarities and differences in letters and words Inability to sound out the pronunciation of an unfamiliar word Difficulty spelling Spending an unusually long-time completing tasks that involve reading or writing Avoiding activities that involve reading Someone with dyslexia can show some of or all of these symptoms, making learning extremely difficult.

Dyslexia and the Brain The science behind dyslexia shows that there are three parts of your brain involved in reading. Neuroimaging studies show that this brain region is less active in individuals with dyslexia. When this part of the brain is lacking in individuals with dyslexia, it can be exceptionally harder to complete school work in an acceptable amount of time. Learning to Manage Dyslexia Learning with dyslexia can be challenging, but it is definitely manageable.

Tagged With: brain function dyslexia education learning disabilities reading. Explore the latest mental wellness tips and discussions, delivered straight to your inbox. Email Address. K on May 30, at pm. How does an adult figure out how to do better when they have dyslexia and have no help? Submit a Comment Cancel reply Your email address will not be published.

Find A Counselor. Popular This Month. Retroactive jealousy in relationships: What to do when your partner obsesses over your past. Does willpower exist? After one year of intervention, we see increased activity in the occipito-temporal region and decreased activity in the right hemisphere important for automatic, fluent reading.

Sharing knowledge about brain functioning is one way of demystifying dyslexia and helps with explaining how the brain functions when language processing is concerned. It is very important for both parents and teachers to truly understand what dyslexia is and is not. Dyslexia and the Brain. Dyslexia and the Brain The continuing research into brain physiology and the connection to dyslexia is providing more answers in order to understand what dyslexia is, how we can diagnose it, how it is related to language and to reading, and the remediation that works.

They show less activity in the right hemisphere. There are metabolic differences in blood flow and physical differences in size. The Brain with Dyslexia Dyslexics show disruptions in the rear reading system in the left hemisphere, critical for reading fluently.

There is more activation in the less efficient right hemisphere, thought to be a compensation method. There is a different distribution of metabolic activation when working on the same tasks as non-dyslexics.

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