The Importance of the Left Occipitotemporal Cortex in Developmental Dyslexia

Kronbichler, Lisa; Kronbichler, Martin

doi:10.1007/s40474-018-0135-4

Cited by 24 publications

(20 citation statements)

References 85 publications

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“…There have been several neuroimaging studies of dyslexia using functional magnetic resonance imaging (fMRI), in which groups of participants with reading difficulties are compared to groups of participants with no difficulties. The results have been summarized in recent reviews (e.g., [ 47 , 48 ]; see also [ 49 , 50 , 51 , 52 , 53 ]). The actual picture from the individual research papers is much noisier than the brief summaries in the reviews might lead one to assume, with many unreliable findings, unreplicated across studies, most likely due to the typically small sample sizes and, possibly, in part due to differences between tasks, sampling criteria, languages, equipment, and statistical analysis software.…”

Section: Functional Neuroimaging Of Dyslexiamentioning

confidence: 99%

“…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 this context, to consider brains that do not lend themselves to efficiently learning to read as exhibiting “anomalies” or “abnormalities” [ 9 , 49 , 50 , 51 , 52 , 53 , 82 ] or to be “abnormal” [ 66 ], “dysfunctional” [ 7 , 58 ], or even “atypical” [ 47 ], without any specific evidence at the individual brain level and without even an understanding of the extent of normal variability, sounds potentially misleading, if not downright inappropriate.…”

Section: Where Does That Leave Us With Dyslexia?mentioning

confidence: 99%

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Is Dyslexia a Brain Disorder?

Protopapas

Parrila

2018

Brain Sciences

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Specific word reading difficulty, commonly termed ‘developmental dyslexia’, refers to the low end of the word reading skill distribution but is frequently considered to be a neurodevelopmental disorder. This term implies that brain development is thought to be disrupted, resulting in an abnormal and dysfunctional brain. We take issue with this view, pointing out that there is no evidence of any obvious neurological abnormality in the vast majority of cases of word reading difficulty cases. The available relevant evidence from neuroimaging studies consists almost entirely of correlational and group-differences studies. However, differences in brains are certain to exist whenever differences in behavior exist, including differences in ability and performance. Therefore, findings of brain differences do not constitute evidence for abnormality; rather, they simply document the neural substrate of the behavioral differences. We suggest that dyslexia is best viewed as one of many expressions of ordinary ubiquitous individual differences in normal developmental outcomes. Thus, terms such as “dysfunctional” or “abnormal” are not justified when referring to the brains of persons with dyslexia.

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Section: Functional Neuroimaging Of Dyslexiamentioning

confidence: 99%

Section: Where Does That Leave Us With Dyslexia?mentioning

confidence: 99%

Is Dyslexia a Brain Disorder?

Protopapas

Parrila

2018

Brain Sciences

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“…Our finding of the group difference between children with RD and controls for the alerting sub-processes in the left occipital lobe could be linked to structural and functional neuroimaging studies of dyslexia (Pugh et al, 2000;Démonet et al, 2004;Richlan, 2012;Xia et al, 2017). A recent review on developmental dyslexia has suggested that left posterior occipitotemporal dysfunction is a secondary deficit area in dyslexia, as it was assumed that phonological processing deficits reflected in the temporoparietal junction would lead to interference with the development of the left occipitotemporal cortex (Kronbichler and Kronbichler, 2018). Therefore, it is possible that atypical processing of visual information in the left occipital regions could be seen in children with RD, even for non-linguistic material.…”

Section: Discussionmentioning

confidence: 62%

Attentional Processes in Children With Attentional Problems or Reading Difficulties as Revealed Using Brain Event-Related Potentials and Their Source Localization

Gopalan

Loberg

Lohvansuu

et al. 2020

Front. Hum. Neurosci.

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Visual attention-related processes include three functional sub-processes: alerting, orienting, and inhibition. We examined these sub-processes using reaction times, eventrelated potentials (ERPs), and their neuronal source activations during the Attention Network Test (ANT) in control children, attentional problems (AP) children, and reading difficulties (RD) children. During the ANT, electroencephalography was measured using 128 electrodes on three groups of Finnish sixth-graders aged 12-13 years (control = 77; AP = 15; RD = 23). Participants were asked to detect the direction of a middle target fish within a group of five fish. The target stimulus was either preceded by a cue (center, double, or spatial), or without a cue, to manipulate the alerting and orienting sub-processes of attention. The direction of the target fish was either congruent or incongruent in relation to the flanker fish, thereby manipulating the inhibition subprocesses of attention. Reaction time performance showed no differences between groups in alerting, orienting, and inhibition effects. The group differences in ERPs were only found at the source level. Neuronal source analysis in the AP children revealed a larger alerting effect (double-cued vs. non-cued target stimuli) than control and RD children in the left occipital lobe. Control children showed a smaller orienting effect (spatially cued vs. center-cued target stimuli) in the left occipital lobe than AP and RD children. No group differences were found for the neuronal sources related to the inhibition effect. The neuronal activity differences related to sub-processes of attention in the AP and RD groups suggest different underlying mechanisms for attentional and reading problems.

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“…Dyslexia is a complex learning disability that affects one's ability to read regardless of intelligence (Siegel, 1989a;Fletcher, 2009). Although the exact cause of dyslexia is still unknown, current hypotheses based primarily on quantitative neuroimaging methods point towards a neurological basis with an emphasis on a left cerebral hemisphere network (Peterson and Pennington, 2012), and in particular the left occipito-temporal cortex (Wandell and Le, 2017;Kronbichler and Kronbichler, 2018). Similarly located anatomical differences have even been seen in pre-readers at risk for dyslexia (Vandermosten et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Myelin Water Imaging Demonstrates Lower Brain Myelination in Children and Adolescents With Poor Reading Ability

Beaulieu

Yip

Low

et al. 2020

Front. Hum. Neurosci.

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Magnetic resonance imaging (MRI) provides a means to non-invasively investigate the neurological links with dyslexia, a learning disability that affects one's ability to read. Most previous brain MRI studies of dyslexia and reading skill have used structural or diffusion imaging to reveal regional brain abnormalities. However, volumetric and diffusion MRI lack specificity in their interpretation at the microstructural level. Myelin is a critical neural component for brain function and plasticity, and as such, deficits in myelin may impact reading ability. MRI can estimate myelin using myelin water fraction (MWF) imaging, which is based on evaluation of the proportion of short T2 myelin-associated water from multiexponential T2 relaxation analysis, but has not yet been applied to the study of reading or dyslexia. In this study, MWF MRI, intelligence, and reading assessments were acquired in 20 participants aged 10-18 years with a wide range of reading ability to investigate the relationship between reading ability and myelination. Group comparisons showed markedly lower MWF by 16-69% in poor readers relative to good readers in the left and right thalamus, as well as the left posterior limb of the internal capsule, left/right anterior limb of the internal capsule, left/right centrum semiovale, and splenium of the corpus callosum. MWF over the entire group also correlated positively with three different reading scores in the bilateral thalamus as well as white matter, including the splenium of the corpus callosum, left posterior limb of the internal capsule, left anterior limb of the internal capsule, and left centrum semiovale. MWF imaging from T2 relaxation suggests that myelination, particularly in the bilateral thalamus, splenium, and left hemisphere white matter, plays a role in reading abilities. Myelin water imaging thus provides a potentially valuable in vivo imaging tool for the study of dyslexia and its remediation.

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The Importance of the Left Occipitotemporal Cortex in Developmental Dyslexia

Cited by 24 publications

References 85 publications

Is Dyslexia a Brain Disorder?

Is Dyslexia a Brain Disorder?

Attentional Processes in Children With Attentional Problems or Reading Difficulties as Revealed Using Brain Event-Related Potentials and Their Source Localization

Myelin Water Imaging Demonstrates Lower Brain Myelination in Children and Adolescents With Poor Reading Ability

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