The Functional Neuroanatomy of Reading Intervention

Atypical characteristic changes of surface morphology and structural covariance network in developmental dyslexia

BACKGROUND

Developmental dyslexia (DD) is a neurodevelopmental disorder that is characterized by difficulties with all aspects of information acquisition in the written word, including slow and inaccurate word recognition. The neural basis behind DD has not been fully elucidated.

METHOD

The study included 22 typically developing (TD) children, 16 children with isolated spelling disorder (SpD), and 20 children with DD. The cortical thickness, folding index, and mean curvature of Broca's area, including the triangular part of the left inferior frontal gyrus (IFGtriang) and the opercular part of the left inferior frontal gyrus, were assessed to explore the differences of surface morphology among the TD, SpD, and DD groups. Furthermore, the structural covariance network (SCN) of the triangular part of the left inferior frontal gyrus was analyzed to explore the changes of structural connectivity in the SpD and DD groups.

RESULTS

The DD group showed higher curvature and cortical folding of the left IFGtriang than the TD group and SpD group. In addition, compared with the TD group and the SpD group, the structural connectivity between the left IFGtriang and the left middle-frontal gyrus and the right mid-orbital frontal gyrus was increased in the DD group, and the structural connectivity between the left IFGtriang and the right precuneus and anterior cingulate was decreased in the DD group.

CONCLUSION

DD had atypical structural connectivity in brain regions related to visual attention, memory and which might impact the information input and integration needed for reading and spelling.

White matter microstructural plasticity associated with educational intervention in reading disability

Children's reading progress typically slows during extended breaks in formal education, such as summer vacations. This stagnation can be especially concerning for children with reading difficulties or disabilities, such as dyslexia, because of the potential to exacerbate the skills gap between them and their peers. Reading interventions can prevent skill loss and even lead to appreciable gains in reading ability during the summer. Longitudinal studies relating intervention response to brain changes can reveal educationally relevant insights into rapid learning-driven brain plasticity. The current work focused on reading outcomes and white matter connections, which enable communication among the brain regions required for proficient reading. We collected reading scores and diffusion-weighted images at the beginning and end of summer for 41 children with reading difficulties who had completed either 1st or 2nd grade. Children were randomly assigned to either receive an intensive reading intervention (n = 26; Seeing Stars from Lindamood-Bell which emphasizes orthographic fluency) or be deferred to a wait-list group (n = 15), enabling us to analyze how white matter properties varied across a wide spectrum of skill development and regression trajectories. On average, the intervention group had larger gains in reading compared to the non-intervention group, who declined in reading scores. Improvements on a proximal measure of orthographic processing (but not other more distal reading measures) were associated with decreases in mean diffusivity within core reading brain circuitry (left arcuate fasciculus and left inferior longitudinal fasciculus) and increases in fractional anisotropy in the left corticospinal tract. Our findings suggest that responses to intensive reading instruction are related predominantly to white matter plasticity in tracts most associated with reading.

A volumetric asymmetry study of gray matter in individuals with and without dyslexia

Brain imaging work aimed at increased classification of dyslexia has underscored an important relationship between anterior (i.e., the inferior frontal gyrus; IFG) and posterior (i.e., superior temporal gyrus and supramarginal gyrus) brain regions. The extent to which the three components of the inferior frontal gyrus, namely the pars orbitalis, triangularis, and opercularis, are differentially related to the posterior regions, namely the superior temporal gyrus and supramarginal gyrus, needs further elucidation. Information about the nature of the anterior-posterior connections would facilitate our understanding of the neural underpinnings associated with dyslexia. Adult participants (N = 38; 16 with dyslexia) took part in an MRI study, whereby high-resolution structural scans were obtained. Volumetric asymmetry of the three regions of the IFG, the superior temporal gyrus, and the supramarginal gyrus was extracted. Significant differences were found for each of the three IFG regions, such that skilled readers had a greater leftward asymmetry of the orbitalis and triangularis, and greater rightward asymmetry of the opercularis, when compared to individuals with dyslexia. Furthermore, the pars triangularis was significantly associated with leftward asymmetry of the superior temporal gyrus for skilled but not dyslexic participants. For individuals with dyslexia, the cortical asymmetry of the IFG, and the corresponding connections with other reading-related brain regions, is inherently different from skilled readers. We discuss our findings in the context of the print-to-speech framework to further our understanding of the neural underpinnings associated with dyslexia.

Characterization of Cortical and Subcortical Structural Brain Asymmetry in Adults with and without Dyslexia

Multiple cortical (planum temporale, supramarginal gyrus, fusiform gyrus) and subcortical (caudate, putamen, and thalamus) regions have shown different functional lateralization patterns for skilled vs. dyslexic readers. The extent to which skilled and dyslexic adult readers show differential structural lateralization remains to be seen. Method: Participants included 72 adults (N = 41 skilled; N = 31 dyslexic) who underwent a high-resolution MRI brain scan. The grey matter volume of the cortical and subcortical structures was extracted. Results: While there were clear behavioral differences between the groups, there were no differences in any of the isolated structures (i.e., either total size or asymmetry index) and limited evidence for any brain-behavior relationships. We did find a significant cortical-cortical relationship (p = 0.006) and a subcortical-subcortical relationship (p = 0.008), but not cross-over relationships. Overall, this work provides unique information on neural structures as they relate to reading in skilled and dyslexic readers.

Reading epilepsy today: A scoping review and meta-analysis of reports of the last three decades

BACKGROUND AND AIM

Reading-induced seizures are presumed to be rare phenomena attributed to an epilepsy syndrome not clearly belonging to either focal or generalized epilepsies. The aim of the article was to summarize knowledge and recent developments in the field of reading-induced seizures by reviewing all cases for which data were reported within the last three decades.

METHODS

A scoping systematic review of demographic, clinical, electroencephalography (EEG) and imaging data of cases with reading-induced seizures reported in PubMed and Web of Science between 1991-01-01 and 2022-08-21 and a meta-analysis of the findings.

RESULTS

The review included 101 case reports of epilepsy with reading-induced seizures (EwRIS) from 42 articles. The phenomenon was more prevalent among males (67, 66.3% vs. 34, 33.7%) with an average age of onset of 18.3 ± 7.9 years. When reported, 30.8% of patients had a family history of epilepsy. Orofacial reflex myocloni (ORM) were the most frequent manifestation (68, 67.3% cases), other presentations, mostly in addition to ORM, included visual, sensory or cognitive symptoms, non-orofacial myoclonic seizures, and absence seizures. Within the sample, 75 (74.3%) patients were identified as having primary reading epilepsy (PRE), 13 (12.9%) idiopathic generalised epilepsy (IGE) and 13 (12.9%) focal epilepsies. Advanced EEG and functional imaging data suggest that the basic mechanism of reading-induced seizures is probably similar despite different symptoms and consists of upregulation of the complex cerebral subsystem involved in reading. Ictogenesis and resulting symptomatology may then depend on predominant sensory or proprioceptive stimuli during reading.

CONCLUSION

In most cases, reading-induced seizures were confirmed to belong to a particular epilepsy syndrome of PRE. However, there were substantial subgroups with IGE and focal epilepsies. Most likely, reading-induced seizures occur as an abnormal response to extero- or proprioceptive input into an upregulated cortical network subserving reading. Most recent researchers consider EwRIS a system epilepsy.

Macular Anatomy Differs in Dyslexic Subjects

The macula, as the central part of the retina, plays an important role in the reading process. However, its morphology has not been previously studied in the context of dyslexia. In this research, we compared the thickness of the fovea, parafovea and perifovea between dyslexic subjects and normal controls, in 11 retinal segmentations obtained by optical coherence tomography (OCT). With this aim, we considered the nine sectors of the Early Treatment Diabetic Retinopathy Study (ETDRS) grid and also summarized data from sectors into inner ring subfield (parafovea) and outer ring subfield (perifovea). The thickness in all the four parafoveal sectors was significantly thicker in the complete retina, inner retina and middle retina of both eyes in the dyslexic group, as well as other macular sectors (fovea and perifovea) in the inner nuclear layer (INL), inner plexiform layer (IPL), IPL + INL and outer plexiform layer + outer nuclear layer (OPL + ONL). Additionally, the inner ring subfield (parafovea), but not the outer ring subfield (perifovea), was thicker in the complete retina, inner retina, middle retina (INL + OPL + ONL), OPL + ONL, IPL + INL and INL in the dyslexic group for both eyes. In contrast, no differences were found between the groups in any of the sectors or subfields of the outer retina, retinal nerve fiber layer, ganglion cell layer or ganglion cell complex in any eye. Thus, we conclude from this exploratory research that the macular morphology differs between dyslexic and normal control subjects, as measured by OCT, especially in the parafovea at middle retinal segmentations.

Dyslexia: Causes and Concomitant Impairments

In recent decades, theories have been presented to explain the nature of dyslexia, but the causes of dyslexia remained unclear. Although the investigation of the causes of dyslexia presupposes a clear understanding of the concept of cause, such an understanding is missing. The present paper proposes the absence of at least one necessary condition or the absence of all sufficient conditions as causes for impaired reading. The causes of impaired reading include: an incorrect fixation location, too short a fixation time, the attempt to recognize too many letters simultaneously, too large saccade amplitudes, and too short verbal reaction times. It is assumed that a longer required fixation time in dyslexic readers results from a functional impairment of areas V1, V2, and V3 that require more time to complete temporal summation. These areas and areas that receive input from them, such as the fusiform gyrus, are assumed to be impaired in their ability to simultaneously process a string of letters. When these impairments are compensated by a new reading strategy, reading ability improves immediately.

The multiple-level framework of developmental dyslexia: the long trace from a neurodevelopmental deficit to an impaired cultural technique

Developmental dyslexia is a neurodevelopmental disorder characterized by an unexpected impairment in literacy acquisition leading to specific poor academic achievement and possible secondary symptoms. The multi-level framework of developmental dyslexia considers five levels of a causal pathway on which a given genotype is expressed and hierarchically transmitted from one level to the next under the increasing influence of individual learning-relevant traits and environmental factors moderated by cultural conditions. These levels are the neurobiological, the information processing and the skill level (prerequisites and acquisition of literacy skills), the academic achievement level and the level of secondary effects. Various risk factors are present at each level within the assumed causal pathway and can increase the likelihood of exhibiting developmental dyslexia. Transition from one level to the next is neither unidirectional nor inevitable. This fact has direct implications for prevention and intervention which can mitigate transitions from one level to the next. In this paper, various evidence-based theories and findings regarding deficits at different levels are placed in the proposed framework. In addition, the moderating effect of cultural impact at and between information processing and skill levels are further elaborated based on a review of findings regarding influences of different writing systems and orthographies. These differences impose culture-specific demands for literacy-specific cognitive procedures, influencing both literacy acquisition and the manifestation of developmental dyslexia.