Coherence motion perception in developmental dyslexia: a meta-analysis of behavioral studies

Visual processing and decision-making in autism and dyslexia: Insights from cross-syndrome approaches

Atypical visual processing has been reported in developmental conditions like autism and dyslexia, and some accounts propose a causal role for visual processing in the development of these conditions. However, few studies make direct comparisons between conditions, or use sufficiently sensitive methods, meaning that it is hard to say whether atypical visual processing tells us anything specific about these conditions, or whether it reflects a more general marker of atypical development. Here I review findings from two computational modelling approaches (equivalent noise and diffusion modelling) and related electroencephalography (EEG) indices which we have applied to data from autistic, dyslexic and typically developing children to reveal how the component processes involved in visual processing and decision-making are altered in autism and dyslexia. The results identify both areas of convergence and divergence in autistic and dyslexic children's visual processing and decision-making, with implications for influential theoretical accounts such as weak central coherence, increased internal noise, and dorsal-stream vulnerability. In both sets of studies, we also see considerable variability across children in all three groups. To better understand this variability, and further understand the convergence and divergence identified between conditions, future studies would benefit from studying how the component processes reviewed here relate to transdiagnostic dimensions, which will also give insights into individual differences in visual processing and decision-making more generally.

The ReadFree tool for the identification of poor readers: a validation study based on a machine learning approach in monolingual and minority-language children

In this study, we validated the "ReadFree tool", a computerised battery of 12 visual and auditory tasks developed to identify poor readers also in minority-language children (MLC). We tested the task-specific discriminant power on 142 Italian-monolingual participants (8-13 years old) divided into monolingual poor readers (N = 37) and good readers (N = 105) according to standardised Italian reading tests. The performances at the discriminant tasks of the "ReadFree tool" were entered into a classification and regression tree (CART) model to identify monolingual poor and good readers. The set of classification rules extracted from the CART model were applied to the MLC's performance and the ensuing classification was compared to the one based on standardised Italian reading tests. According to the CART model, auditory go-no/go (regular), RAN and Entrainment100bpm were the most discriminant tasks. When compared with the clinical classification, the CART model accuracy was 86% for the monolinguals and 76% for the MLC. Executive functions and timing skills turned out to have a relevant role in reading. Results of the CART model on MLC support the idea that ad hoc standardised tasks that go beyond reading are needed.

Understanding perceptual decisions by studying development and neurodiversity

A cornerstone of human information processing is how we make decisions about incoming sensory percepts. Much of psychological science has focused on understanding how these judgements operate in skilled adult observers. While not typically the focus of this research, there is considerable variability in how adults make these judgements. Here, we review complementary computational modelling, electrophysiological data, eye-tracking and longitudinal approaches to the study of perceptual decisions across neurotypical development and in neurodivergent individuals. These data highlight multiple parameters and temporal dynamics feeding into how we become skilled adult perceptual decision makers, and which may help explain why we vary so much in how we make perceptual decisions.

Visual motion processing in Chinese children with developmental dyslexia: An fMRI study

Dorsal stream is an important pathway for visual information transmission. As a part of the dorsal pathway, the middle temporal visual motion areas (V5/MT+) are mainly responsible for visual motion processing and the ability of visual motion processing is closely related to reading. Compared with alphabetic scripts, the visual structure of Chinese characters is more complex and there are no clear grapheme-phoneme correspondence rules. So the ability of visual analysis plays an important role in Chinese character processing. This study first investigated the brain activation of Chinese dyslexic children and children of the same chronological age when they observed coherent motion stimuli. ROI analysis indicated that only the activation of left V5/MT+ was significantly weaker in dyslexics than that in the control group. The activity of the magnocellular-dorsal stream was closely related to orthographic awareness in the combined data (two groups) and the typical children. In dyslexia group, the stronger the activation of V5/MT+ was, the worse the phonological awareness, rapid naming performance and orthographic awareness were. In short, Chinese dyslexic children were deficient in the activation of the left V5/MT+ and the activity of the magnocellular-dorsal pathway was closely related to orthographic awareness in Chinese pupils.

Integration of visual motion and orientation signals in dyslexic children: an equivalent noise approach

Dyslexic individuals have been reported to have reduced global motion sensitivity, which could be attributed to various causes including atypical magnocellular or dorsal stream function, impaired spatial integration, increased internal noise and/or reduced external noise exclusion. Here, we applied an equivalent noise experimental paradigm alongside a traditional motion-coherence task to determine what limits global motion processing in dyslexia. We also presented static analogues of the motion tasks (orientation tasks) to investigate whether perceptual differences in dyslexia were restricted to motion processing. We compared the performance of 48 dyslexic and 48 typically developing children aged 8 to 14 years in these tasks and used equivalent noise modelling to estimate levels of internal noise (the precision associated with estimating each element's direction/orientation) and sampling (the effective number of samples integrated to judge the overall direction/orientation). While group differences were subtle, dyslexic children had significantly higher internal noise estimates for motion discrimination, and higher orientation-coherence thresholds, than typical children. Thus, while perceptual differences in dyslexia do not appear to be restricted to motion tasks, motion and orientation processing seem to be affected differently. The pattern of results also differs from that previously reported in autistic children, suggesting perceptual processing differences are condition-specific.

Behavioural and neural indices of perceptual decision-making in autistic children during visual motion tasks

Many studies report atypical responses to sensory information in autistic individuals, yet it is not clear which stages of processing are affected, with little consideration given to decision-making processes. We combined diffusion modelling with high-density EEG to identify which processing stages differ between 50 autistic and 50 typically developing children aged 6-14 years during two visual motion tasks. Our pre-registered hypotheses were that autistic children would show task-dependent differences in sensory evidence accumulation, alongside a more cautious decision-making style and longer non-decision time across tasks. We tested these hypotheses using hierarchical Bayesian diffusion models with a rigorous blind modelling approach, finding no conclusive evidence for our hypotheses. Using a data-driven method, we identified a response-locked centro-parietal component previously linked to the decision-making process. The build-up in this component did not consistently relate to evidence accumulation in autistic children. This suggests that the relationship between the EEG measure and diffusion-modelling is not straightforward in autistic children. Compared to a related study of children with dyslexia, motion processing differences appear less pronounced in autistic children. Exploratory analyses also suggest weak evidence that ADHD symptoms moderate perceptual decision-making in autistic children.

Enhanced reading abilities is modulated by faster visual spatial attention

Research has shown improved reading following visual magnocellular training in individuals with dyslexia. Many studies have demonstrated how the magnocellular pathway controls visual spatial attention. Therefore, we have investigated the relationship between magnocellular pathway and visual spatial attention deficits in dyslexia in order to better understand how magnocellular-based interventions may help children to learn to read. Magnocellular function, visual spatial attention, and reading abilities of thirty elementary school students with dyslexia, aged between 8 and 10, were measured. The experimental group received magnocellular-based visual motion training for 12 sessions, while the control group received neutral sessions. All tests were repeated at the end of the training and after 1 month. The magnocellular functioning, visual spatial attention, and reading abilities of the experimental group improved significantly compared to the controls. Additionally, improvement in reaction time of invalid conditions predicted improvements in saccadic eye movements. We conclude that visual magnocellular training improved saccadic eye movement control, visual spatial orientation, and reading ability.

Visual Motion and Decision-Making in Dyslexia: Reduced Accumulation of Sensory Evidence and Related Neural Dynamics

Children with and without dyslexia differ in their behavioral responses to visual information, particularly when required to pool dynamic signals over space and time. Importantly, multiple processes contribute to behavioral responses. Here we investigated which processing stages are affected in children with dyslexia when performing visual motion processing tasks, by combining two methods that are sensitive to the dynamic processes leading to responses. We used a diffusion model which decomposes response time and accuracy into distinct cognitive constructs, and high-density EEG. Fifty children with dyslexia (24 male) and 50 typically developing children (28 male) 6-14 years of age judged the direction of motion as quickly and accurately as possible in two global motion tasks (motion coherence and direction integration), which varied in their requirements for noise exclusion. Following our preregistered analyses, we fitted hierarchical Bayesian diffusion models to the data, blinded to group membership. Unblinding revealed reduced evidence accumulation in children with dyslexia compared with typical children for both tasks. Additionally, we identified a response-locked EEG component which was maximal over centro-parietal electrodes which indicated a neural correlate of reduced drift rate in dyslexia in the motion coherence task, thereby linking brain and behavior. We suggest that children with dyslexia tend to be slower to extract sensory evidence from global motion displays, regardless of whether noise exclusion is required, thus furthering our understanding of atypical perceptual decision-making processes in dyslexia.SIGNIFICANCE STATEMENT Reduced sensitivity to visual information has been reported in dyslexia, with a lively debate about whether these differences causally contribute to reading difficulties. In this large preregistered study with a blind modeling approach, we combine state-of-the art methods in both computational modeling and EEG analysis to pinpoint the stages of processing that are atypical in children with dyslexia in two visual motion tasks that vary in their requirement for noise exclusion. We find reduced evidence accumulation in children with dyslexia across both tasks, and identify a neural marker, allowing us to link brain and behavior. We show that children with dyslexia exhibit general difficulties with extracting sensory evidence from global motion displays, not just in tasks that require noise exclusion.

Reduced 2D form coherence and 3D structure from motion sensitivity in developmental dyscalculia

Developmental dyscalculia (DD) is a specific learning disability affecting the development of numerical and arithmetical skills. The origin of DD is typically attributed to the suboptimal functioning of key regions within the dorsal visual stream (parietal cortex) which support numerical cognition. While DD individuals are often impaired in visual numerosity perception, the extent to which they also show a wider range of visual dysfunctions is poorly documented. In the current study we measured sensitivity to global motion (translational and flow), 2D static form (Glass patterns) and 3D structure from motion in adults with DD and control subjects. While sensitivity to global motion was comparable across groups, thresholds for static form and structure from motion were higher in the DD compared to the control group, irrespective of associated reading impairments. Glass pattern sensitivity predicted numerical abilities, and this relation could not be explained by recently reported differences in visual crowding. Since global form sensitivity has often been considered an index of ventral stream function, our findings could indicate a cortical dysfunction extending beyond the dorsal visual stream. Alternatively, they would fit with a role of parietal cortex in form perception under challenging conditions requiring multiple element integration.

Global motion evoked potentials in autistic and dyslexic children: A cross-syndrome approach

Atypicalities in psychophysical thresholds for global motion processing have been reported in many neurodevelopmental conditions, including autism and dyslexia. Cross-syndrome comparisons of neural dynamics may help determine whether altered motion processing is a general marker of atypical development or condition-specific. Here, we assessed group differences in N2 peak amplitude (previously proposed as a marker of motion-specific processing) in typically developing (n = 57), autistic (n = 29) and dyslexic children (n = 44) aged 6-14 years, in two global motion tasks. High-density EEG data were collected while children judged the direction of global motion stimuli as quickly and accurately as possible, following a period of random motion. Using a data-driven component decomposition technique, we identified a reliable component that was maximal over occipital electrodes and had an N2-like peak at ~160 msec. We found no group differences in N2 peak amplitude, in either task. However, for both autistic and dyslexic children, there was evidence of atypicalities in later stages of processing that require follow up in future research. Our results suggest that early sensory encoding of motion information is unimpaired in dyslexic and autistic children. Group differences in later processing stages could reflect sustained global motion responses, decision-making, metacognitive processes and/or response generation, which may also distinguish between autistic and dyslexic individuals.

White matter deficits correlate with visual motion perception impairments in dyslexic carriers of the DCDC2 genetic risk variant

Motion perception deficits in dyslexia show a large intersubjective variability, partly reflecting genetic factors influencing brain architecture development. In previous work, we have demonstrated that dyslexic carriers of a mutation of the DCDC2 gene have a very strong impairment in motion perception. In the present study, we investigated structural white matter alterations associated with the poor motion perception in a cohort of twenty dyslexics with a subgroup carrying the DCDC2 gene deletion (DCDC2d+) and a subgroup without the risk variant (DCDC2d–). We observed significant deficits in motion contrast sensitivity and in motion direction discrimination accuracy at high contrast, stronger in the DCDC2d+ group. Both motion perception impairments correlated significantly with the fractional anisotropy in posterior ventral and dorsal tracts, including early visual pathways both along the optic radiation and in proximity of occipital cortex, MT and VWFA. However, the DCDC2d+ group showed stronger correlations between FA and motion perception impairments than the DCDC2d– group in early visual white matter bundles, including the optic radiations, and in ventral pathways located in the left inferior temporal cortex. Our results suggest that the DCDC2d+ group experiences higher vulnerability in visual motion processing even at early stages of visual analysis, which might represent a specific feature associated with the genotype and provide further neurobiological support to the visual-motion deficit account of dyslexia in a specific subpopulation.

The role of visual-spatial attention in reading development: a meta-analysis

The association between visual attention and reading development has been investigated as a possible core causal deficit in dyslexia, in addition to phonological awareness. This study aims to provide a meta-analytic review of the research on attentional processes and their relation to reading development, to examine the possible influence on it of orthographic depth, age, and attentional tasks (interpreted as serial or parallel processing indices). We included studies with participants up to 18 years of age that have considered the visual spatial attention orienting that sustains the serial visual analysis involved in the phonological pathway of decoding, and the visual attention span that supports the multielement parallel processing that is thought to influence lexical decoding. The results confirm a strong association between visual attention and reading development; we evaluate the evidence and discuss the possibility that visual attention processes play a causal role in determining individual differences in reading acquisition.

Motion perception and its disorders

As we live in a dynamic world, motion is a fundamental aspect of our visual experience. The advent of computerized stimuli has allowed controlled study of a wide array of motion phenomena, including global integration and segmentation, speed and direction discrimination, motion aftereffects, the optic flow that accompanies self-motion, perception of object form derived from motion cues, and point-light biological motion. Animal studies first revealed the existence of a motion-selective region, the middle temporal (MT) area, also known as V5, located in the lateral occipitotemporal cortex, followed by areas such as V5A (also known as MST, the middle superior temporal area), V6/V6A, the ventral intraparietal area, and others. In humans there are rare cases of bilateral lesions of the V5/V5A complex causing cerebral akinetopsia, a severe impairment of motion perception. Unilateral V5/V5A lesions are more common but cause milder asymptomatic deficits, often limited to the contralateral hemifield, while parietal lesions can impair perception of point-light biological motion or high-level motion tasks that are attentionally demanding. Impairments of motion perception have also been described in optic neuropathy, particularly glaucoma, as well as Alzheimer's disease, Parkinson's disease with dementia, and dementia with Lewy body disease. Prematurity with or without periventricular leukomalacia and developmental syndromes such as Williams' syndrome, autism, and dyslexia have also been associated with impaired motion perception, suggesting a developmental vulnerability of the dorsal pathway.

Altered electroencephalographic networks in developmental dyslexia after remedial training: a prospective case-control study

Electroencephalographic studies using graph theoretic analysis have found aberrations in functional connectivity in children with developmental dyslexia. However, how the training with visual tasks can change the functional connectivity of the semantic network in developmental dyslexia is still unclear. We looked for differences in local and global topological properties of functional networks between 21 healthy controls and 22 dyslexic children (8-9 years old) before and after training with visual tasks in this prospective case-control study. The minimum spanning tree method was used to construct the subjects' brain networks in multiple electroencephalographic frequency ranges during a visual word/pseudoword discrimination task. We found group differences in the theta, alpha, beta and gamma bands for four graph measures suggesting a more integrated network topology in dyslexics before the training compared to controls. After training, the network topology of dyslexic children had become more segregated and similar to that of the controls. In the θ, α and β1-frequency bands, compared to the controls, the pre-training dyslexics exhibited a reduced degree and betweenness centrality of the left anterior temporal and parietal regions. The simultaneous appearance in the left hemisphere of hubs in temporal and parietal (α, β1), temporal and superior frontal cortex (θ, α), parietal and occipitotemporal cortices (β1), identified in the networks of normally developing children was not present in the brain networks of dyslexics. After training, the hub distribution for dyslexics in the theta and beta1 bands had become similar to that of the controls. In summary, our findings point to a less efficient network configuration in dyslexics compared to a more optimal global organization in the controls. This is the first study to investigate the topological organization of functional brain networks of Bulgarian dyslexic children. Approval for the study was obtained from the Ethics Committee of the Institute of Neurobiology and the Institute for Population and Human Studies, Bulgarian Academy of Sciences (approval No. 02-41/12.07.2019) on March 28, 2017, and the State Logopedic Center and the Ministry of Education and Science (approval No. 09-69/14.03.2017) on July 12, 2019.

Developmental trajectories of global motion and global form perception from 4 years to adulthood

Literature on the development of global motion and global form perception demonstrated their asynchronous developmental trajectories. However, former studies have failed to clearly establish the critical period of maturation for these specific abilities. This study aimed to analyze the developmental trajectories of global motion and global form discrimination abilities by controlling for basic visual functions and general cognitive ability and to present the global motion and global form normative scores. A sample of 456 children and adolescents (4-17 years of age) and 76 adults recruited from the Italian and Swedish general population participated in the study. Motion and form perception were evaluated by the motion coherence test and form coherence test, respectively. Raven's matrices were used to assess general cognitive ability, the Lea Hyvärinen chart test was used for full- and low-contrast visual acuity, and the TNO test was used for stereopsis. General cognitive ability and basic visual functions were strongly related to motion and form perception development. Global motion perception had an accelerated maturation compared with global form perception. For motion perception, an analysis of the oblique effect's development showed that it is present at 4 years of age. The standardized scores of global motion and form coherence tests can be used for clinical purposes.

Reading-Network in Developmental Dyslexia before and after Visual Training

Electroencephalographic studies using graph-theoretic analysis have found aberrations in functional connectivity in dyslexics. How visual nonverbal training (VT) can change the functional connectivity of the reading network in developmental dyslexia is still unclear. We studied differences in the local and global topological properties of functional reading networks between controls and dyslexic children before and after VT. The minimum spanning tree method was used to construct the reading networks in multiple electroencephalogram (EEG) frequency bands. Compared to controls, pre-training dyslexics had a higher leaf fraction, tree hierarchy, kappa, and smaller diameter (θ—γ-frequency bands), and therefore, they had a less segregated neural network than controls. After training, the reading-network metrics of dyslexics became similar to controls. In β1 and γ-frequency bands, pre-training dyslexics exhibited a reduced degree and betweenness centrality of hubs in superior, middle, and inferior frontal areas in both brain hemispheres compared to the controls. Dyslexics relied on the left anterior temporal (β1, γ1) and dorsolateral prefrontal cortex (γ1), while in the right hemisphere, they relied on the occipitotemporal, parietal, (β1), motor (β2, γ1), and somatosensory cortices (γ1). After training, hubs appeared in both hemispheres at the middle occipital (β), parietal (β1), somatosensory (γ1), and dorsolateral prefrontal cortices (γ2), while in the left hemisphere, they appeared at the middle temporal, motor (β1), intermediate (γ2), and inferior frontal cortices (γ1, β2). Language-related brain regions were more active after visual training. They contribute to an understanding of lexical and sublexical representation. The same role has areas important for articulatory processes of reading.

Advantage of detecting visual events in the right hemifield is affected by reading skill

Visual perception is often not homogenous across the visual field and can vary depending on situational demands. The reasons behind this inhomogeneity are not clear. Here we show that directing attention that is consistent with a western reading habit from left to right, results in a ~32% higher sensitivity to detect transient visual events in the right hemifield. This right visual field advantage was largely reduced in individuals with reading difficulties from developmental dyslexia. Similarly, visual detection became more symmetric in skilled readers, when attention was guided opposite to the reading pattern. Taken together, these findings highlight a higher sensitivity in the right visual field for detecting the onset of sudden visual events that is well accounted for by left hemisphere dominated reading habit.

Auditory frequency discrimination in developmental dyslexia: A meta-analysis

Auditory frequency discrimination has been used as an index of sensory processing in developmental language disorders such as dyslexia, where group differences have often been interpreted as evidence for a basic deficit in auditory processing that underpins and constrains individual variability in the development of phonological skills. Here, we conducted a meta-analysis to evaluate the cumulative evidence for group differences in frequency discrimination and to explore the impact of some potential moderator variables that could contribute to variability in effect-size estimations across studies. Our analyses revealed mean effect sizes for group differences on frequency discrimination tasks on the order of three-quarters of a standard deviation, but in the presence of substantial inter-study variability in their magnitude. Moderator variable analyses indicated that factors related both to participant variability on behavioural and cognitive variables associated with the dyslexia phenotype, and to variability in the task design, contributed to differences in the magnitude of effect size across studies. The apparently complex pattern of results was compounded by the lack of concurrent, standardised metrics of cognitive and reading component skills across the constituent studies. Differences on sensory processing tasks are often reported in studies of developmental disorders, but these need to be more carefully interpreted in the context of non-sensory factors, which may explain significant inter- and intra-group variance in the dependent measure of interest.

Global Motion Perception in Autism Spectrum Disorder: A Meta-Analysis

Visual perception in individuals with autism spectrum disorder (ASD) is often debated in terms of enhanced local and impaired global perception. Deficits in global motion perception seem to support this characterization, although the evidence is inconsistent. We conducted a large meta-analysis on global motion, combining 48 articles on biological and coherent motion. Results provide evidence for a small global motion processing deficit in individuals with ASD compared to controls in both biological and coherent motion. This deficit appears to be present independent of the paradigm, task, dependent variable, age or IQ of the groups. Results indicate that individuals with ASD are less sensitive to these types of global motion, although the difference in neural mechanisms underlying this behavioral difference remains unclear.

Beyond the global motion deficit hypothesis of developmental dyslexia: A cross-sectional study of visual, cognitive, and socio-economic factors influencing reading ability in children

Although primarily conceptualized as a disorder of phonological awareness, developmental dyslexia is often associated with broader problems perceiving and attending to transient or rapidly-moving visual stimuli. However, the extent to which such visual deficits represent the cause or the consequence of dyslexia remains contentious, and very little research has examined the relative contributions of phonological, visual, and other variables to reading performance more broadly. We measured visual sensitivity to global motion (GM) and global form (GF), performance on various language and other cognitive tasks believed to be compromised in dyslexia (phonological awareness, processing speed, and working memory), together with a range of social and demographic variables often omitted in previous research, such as age, gender, non-verbal intelligence, and socio-economic status in an unselected sample (n = 132) of children aged 6-11.5 yrs from two different primary schools in Edinburgh, UK. We found that: (i) Mean GM sensitivity (but not GF) was significantly lower in poor readers (medium effect size); (ii) GM sensitivity accounted for only 3% of the variance in reading scores; (iii) GM sensitivity deficits were observed in only 16% of poor readers; (iv) the best predictors of reading performance were phonological awareness, non-verbal intelligence, and socio-economic status, suggesting the importance of controlling for these in future studies of vision and reading. These findings suggest that developmental dyslexia is unlikely to represent a single category of neurodevelopmental disorder underpinned by lower-level deficits in visual motion processing.

Magnocellular Based Visual Motion Training Improves Reading in Persian

The visual magnocellular system is thought to play a crucial role in learning to read. Here therefore, we examined whether magnocellular based training could improve reading in children with visual reading problems. The participants were 24 male primary school students aged between 9–11 (Mean = 9.76, SD = 0.59) with specific reading difficulty. Experimental and control groups were matched for age, sex, educational level, IQ, reading abilities (measured by APRA), magnocellular performance as assessed by a random dot kinematogram (RDK) paradigm and recordings of their saccadic eye movements. The experimental group received twelve magnocellular based visual motion training sessions, twice a week over 6 weeks. During the same period, the control group played a video game with the help of a practitioner. All measures were made just prior to the training and were repeated at the 6^th, 12^th training session and one month later. The experimental group showed significant improvements in magnocellular function, visual errors and reading accuracy during the course of intervention. Follow-up assessment confirmed that these effects persisted one month later. Impaired magnocellular functioning appeared to be an important cause of poor reading in Persian. Hence magnocellular based training could help many children with specific reading difficulties. Also testing magnocellular function could be used as screening tool for detecting dyslexia before a child begins to fail at school.

It is the egg, not the chicken; dorsal visual deficits present in dyslexia are not present in illiterate adults

Some individuals with dyslexia demonstrate deficits in reading, visual attention, and visual processing which can be attributed to a functional failure of the magnocells in the visual system or in the dorsal visual pathway. The study examines the role of magno/dorsal function in dyslexic adults compared with normal, illiterate, and semi-literate readers. Coherent motion and coherent form were used in Experiment 1, and the frequency doubling illusion and static-gratings were used in Experiment 2. If a magno/dorsal deficit is demonstrated for dyslexic readers but not illiterate, semi-literate, and normal reading adults, then the deficit cannot be attributed to reading experience. Illiterate adults performed the same as normal and semi-literate readers in coherent motion and frequency doubling tasks, and all three groups performed better than the dyslexic readers. There was no difference between any of the groups in the coherent form or static grating tasks. Together, these studies show that illiterate and semi-literate adults do not demonstrate a magno/dorsal deficit that is a characteristic of some sufferers of dyslexia. Therefore, magno/dorsal deficits in dyslexia are unlikely to be a consequence of failing to learn to read but rather provides evidence to suggest a causal role for reduced visual magno/dorsal processing.

Tablet computer games to measure dorsal stream performance in good and poor readers

Evidence suggests a link between deficits in visuo-spatial attention, and subsequent reading ability. However, all the research in the area thus far has been conducted using traditional, lab-based psychophysics, with very tightly controlled visual parameters. In order to take this research further, such as using visuo-spatial tasks for remediation purposes, it must be established that such tasks can be taken out of the laboratory, 'gamified', and still predict reading ability. This study aimed to determine if subtle visual deficits in poor readers could be detected outside a traditional laboratory, in relatively uncontrolled settings using portable game-like technology. Classic visual search and change detection programs, thought to rely on the visual dorsal stream, were modified to a game-like format. They were administered on a portable computer tablet within the participants' school setting. Whilst IQ predicted reading rate, visuo-spatial tasks such as visual search speed, and change detection, each accounted for unique variance in reading rate over and above IQ, age and phonological ability. These results are consistent with the visuo-spatial attention deficit hypothesis, and provide support for the development of portable computerised games that may assess and potentially target this deficit in poor readers.

Meta-analytic findings reveal lower means but higher variances in visuospatial ability in dyslexia

Conflicting empirical and theoretical accounts suggest that dyslexia is associated with either average, enhanced, or impoverished high-level visuospatial processing relative to controls. Such heterogeneous results could be due to the presence of wider variability in dyslexic samples, which is unlikely to be identified at the single study level, due to lack of power. To address this, this study reports a meta-analysis of means and variances in high-level visuospatial ability in 909 non-dyslexic and 956 dyslexic individuals. The findings suggest that dyslexia is associated not only with a lower mean performance on visuospatial tasks but also with greater variability in performance. Through novel meta-analytic techniques, we demonstrate a negative effect size for mean differences (-.457), but a positive effect size for SD differences (+.118; SD ratio = 1.107). In doing so, this is the first study to demonstrate impoverished visuospatial processing of the majority of individuals with dyslexia in addition to greater variance in performance in this group. The findings advocate for further consideration of both the presence of, and reasons for, increased variance in perception, attention, and memory across neurodevelopmental disorders.

Reading deficits in schizophrenia and their relationship to developmental dyslexia: A review

Although schizophrenia and developmental dyslexia are considered distinct disorders in terms of clinical presentation and functional outcome, they both involve disruption in the processes that support skilled reading, including language, auditory perception, visual perception, oculomotor control, and executive function. Further, recent work has proposed a common neurodevelopmental basis for the two disorders, as suggested by genetic and pathophysiological overlap. Thus, these lines of research suggest that reading may be similarly impacted in schizophrenia and dyslexia. In this review, we survey research on reading abilities in individuals with schizophrenia, and review the potential mechanisms underlying reading deficits in schizophrenia that may be shared with those implicated in dyslexia. Elucidating the relationship between reading impairment in schizophrenia and dyslexia could allow for a better understanding of the pathophysiological underpinnings of schizophrenia, and could facilitate remediation of cognitive deficits that impact day-to-day functioning.

Visual perception in dyslexia is limited by sub-optimal scale selection

Readers with dyslexia are purported to have a selective visual impairment but the underlying nature of the deficit remains elusive. Here, we used a combination of behavioural psychophysics and biologically-motivated computational modeling to investigate if this deficit extends to object segmentation, a process implicated in visual word form recognition. Thirty-eight adults with a wide range of reading abilities were shown random-dot displays spatially divided into horizontal segments. Adjacent segments contained either local motion signals in opposing directions or analogous static form cues depicting orthogonal orientations. Participants had to discriminate these segmented patterns from stimuli containing identical motion or form cues that were spatially intermingled. Results showed participants were unable to perform the motion or form task reliably when segment size was smaller than a spatial resolution (acuity) limit that was independent of reading skill. Coherence thresholds decreased as segment size increased, but for the motion task the rate of improvement was shallower for readers with dyslexia and the segment size where performance became asymptotic was larger. This suggests that segmentation is impaired in readers with dyslexia but only on tasks containing motion information. We interpret these findings within a novel framework in which the mechanisms underlying scale selection are impaired in developmental dyslexia.

The DCDC2 deletion is not a risk factor for dyslexia

Dyslexia is a specific impairment in learning to read and has strong heritability. An intronic deletion within the DCDC2 gene, with ~8% frequency in European populations, is increasingly used as a marker for dyslexia in neuroimaging and behavioral studies. At a mechanistic level, this deletion has been proposed to influence sensory processing capacity, and in particular sensitivity to visual coherent motion. Our re-assessment of the literature, however, did not reveal strong support for a role of this specific deletion in dyslexia. We also analyzed data from five distinct cohorts, enriched for individuals with dyslexia, and did not identify any signal indicative of associations for the DCDC2 deletion with reading-related measures, including in a combined sample analysis (N=526). We believe we conducted the first replication analysis for a proposed deletion effect on visual motion perception and found no association (N=445 siblings). We also report that the DCDC2 deletion has a frequency of 37.6% in a cohort representative of the general population recruited in Hong Kong (N=220). This figure, together with a lack of association between the deletion and reading abilities in this cohort, indicates the low likelihood of a direct deletion effect on reading skills. Therefore, on the basis of multiple strands of evidence, we conclude that the DCDC2 deletion is not a strong risk factor for dyslexia. Our analyses and literature re-evaluation are important for interpreting current developments within multidisciplinary studies of dyslexia and, more generally, contribute to current discussions about the importance of reproducibility in science.

Training on Movement Figure-Ground Discrimination Remediates Low-Level Visual Timing Deficits in the Dorsal Stream, Improving High-Level Cognitive Functioning, Including Attention, Reading Fluency, and Working Memory

The purpose of this study was to determine whether neurotraining to discriminate a moving test pattern relative to a stationary background, figure-ground discrimination, improves vision and cognitive functioning in dyslexics, as well as typically-developing normal students. We predict that improving the speed and sensitivity of figure-ground movement discrimination (PATH to Reading neurotraining) acts to remediate visual timing deficits in the dorsal stream, thereby improving processing speed, reading fluency, and the executive control functions of attention and working memory in both dyslexic and normal students who had PATH neurotraining more than in those students who had no neurotraining. This prediction was evaluated by measuring whether dyslexic and normal students improved on standardized tests of cognitive skills following neurotraining exercises, more than following computer-based guided reading (Raz-Kids (RK)). The neurotraining used in this study was visually-based training designed to improve magnocellular function at both low and high levels in the dorsal stream: the input to the executive control networks coding working memory and attention. This approach represents a paradigm shift from the phonologically-based treatment for dyslexia, which concentrates on high-level speech and reading areas. This randomized controlled-validation study was conducted by training the entire second and third grade classrooms (42 students) for 30 min twice a week before guided reading. Standardized tests were administered at the beginning and end of 12-weeks of intervention training to evaluate improvements in academic skills. Only movement-discrimination training remediated both low-level visual timing deficits and high-level cognitive functioning, including selective and sustained attention, reading fluency and working memory for both dyslexic and normal students. Remediating visual timing deficits in the dorsal stream revealed the causal role of visual movement discrimination training in improving high-level cognitive functions such as attention, reading acquisition and working memory. This study supports the hypothesis that faulty timing in synchronizing the activity of magnocellular with parvocellular visual pathways in the dorsal stream is a fundamental cause of dyslexia and being at-risk for reading problems in normal students, and argues against the assumption that reading deficiencies in dyslexia are caused by phonological or language deficits, requiring a paradigm shift from phonologically-based treatment of dyslexia to a visually-based treatment. This study shows that visual movement-discrimination can be used not only to diagnose dyslexia early, but also for its successful treatment, so that reading problems do not prevent children from readily learning.

Psychophysical measurements in children: challenges, pitfalls, and considerations

Measuring sensory sensitivity is important in studying development and developmental disorders. However, with children, there is a need to balance reliable but lengthy sensory tasks with the child’s ability to maintain motivation and vigilance. We used simulations to explore the problems associated with shortening adaptive psychophysical procedures, and suggest how these problems might be addressed. We quantify how adaptive procedures with too few reversals can over-estimate thresholds, introduce substantial measurement error, and make estimates of individual thresholds less reliable. The associated measurement error also obscures group differences. Adaptive procedures with children should therefore use as many reversals as possible, to reduce the effects of both Type 1 and Type 2 errors. Differences in response consistency, resulting from lapses in attention, further increase the over-estimation of threshold. Comparisons between data from individuals who may differ in lapse rate are therefore problematic, but measures to estimate and account for lapse rates in analyses may mitigate this problem.

Encoding of rapid time-varying information is impaired in poor readers

A characteristic set of eye movements and fixations are made during reading, so the position of words on the retinae is constantly being updated. Effective decoding of print requires this temporal stream of visual information to be segmented or parsed into its constituent units (e.g., letters or words). Poor readers' difficulties with word recognition could arise at the point of segmenting time-varying visual information, but the mechanisms underlying this process are little understood. Here, we used random-dot displays to explore the effects of reading ability on temporal segmentation. Thirty-eight adult readers viewed test stimuli that were temporally segmented by constraining either local motions or analogous form cues to oscillate back and fourth at each of a range of rates. Participants had to discriminate these segmented patterns from comparison stimuli containing the same motion and form cues but these were temporally intermingled. Results showed that the motion and form tasks could not be performed reliably when segment duration was shorter than a temporal resolution (acuity) limit. The acuity limits for both tasks were significantly and negatively correlated with reading scores. Importantly, the minimum segment duration needed to detect the temporally segmented stimuli was longer in relatively poor readers than relatively good readers. This demonstrates that adult poor readers have difficulty segmenting temporally changing visual input particularly at short segment durations. These results are consistent with evidence suggesting that precise encoding of rapid time-varying information is impaired in developmental dyslexia.

Visual dorsal stream is associated with Chinese reading skills: A resting-state fMRI study

The present study explored the relationship between visual dorsal stream and Chinese reading by resting-state fMRI technique. We collected the resting-state brain activities and reading skills of Chinese-speaking adult readers. The results showed that the values of amplitude of low frequency fluctuation (ALFF) in right posterior parietal cortex (PPC) and left visual middle temporal area (MT) (two regions of dorsal stream) were significantly correlated with rapid naming (RAN) speed, and the ALFF values of right PPC were correlated with orthographic awareness (OA). Further resting-state functional connectivity (RSFC) analysis revealed that RAN speed was related to RSFCs between dorsal stream areas and reading areas (e.g., left fusiform gyrus, bilateral middle occipital gyrus). OA was correlated with RSFCs between right PPC and left middle occipital gyrus. It suggested that spontaneous activities of visual dorsal stream, as well as connection between it and reading-related areas, were highly associated with Chinese reading skills.

Global Visual Motion Sensitivity: Associations with Parietal Area and Children's Mathematical Cognition

Sensitivity to global visual motion has been proposed as a signature of brain development, related to the dorsal rather than ventral cortical stream. Thresholds for global motion have been found to be elevated more than for global static form in many developmental disorders, leading to the idea of "dorsal stream vulnerability." Here we explore the association of global motion thresholds with individual differences in children's brain development, in a group of typically developing 5- to 12-year-olds. Good performance was associated with a relative increase in parietal lobe surface area, most strongly around the intraparietal sulcus and decrease in occipital area. In line with the involvement of intraparietal sulcus, areas in visuospatial and numerical cognition, we also found that global motion performance was correlated with tests of visuomotor integration and numerical skills. Individual differences in global form detection showed none of these anatomical or cognitive correlations. This suggests that the correlations with motion sensitivity are unlikely to reflect general perceptual or attentional abilities required for both form and motion. We conclude that individual developmental variations in global motion processing are not linked to greater area in the extrastriate visual areas, which initially process such motion, but in the parietal systems that make decisions based on this information. The overlap with visuospatial and numerical abilities may indicate the anatomical substrate of the "dorsal stream vulnerability" proposed as characterizing neurodevelopmental disorders.

Why is the processing of global motion impaired in adults with developmental dyslexia?

Individuals with dyslexia are purported to have a selective dorsal stream impairment that manifests as a deficit in perceiving visual global motion relative to global form. However, the underlying nature of the visual deficit in readers with dyslexia remains unclear. It may be indicative of a difficulty with motion detection, temporal processing, or any task that necessitates integration of local visual information across multiple dimensions (i.e. both across space and over time). To disentangle these possibilities we administered four diagnostic global motion and global form tasks to a large sample of adult readers (N=106) to characterise their perceptual abilities. Two sets of analyses were conducted. First, to investigate if general reading ability is associated with performance on the visual tasks across the entire sample, a composite reading score was calculated and entered into a series of continuous regression analyses. Next, to investigate if the performance of readers with dyslexia differs from that of good readers on the visual tasks we identified a group of forty-three individuals for whom phonological decoding was specifically impaired, consistent with the dyslexic profile, and compared their performance with that of good readers who did not exhibit a phonemic deficit. Both analyses yielded a similar pattern of results. Consistent with previous research, coherence thresholds of poor readers were elevated on a random-dot global motion task and a spatially one-dimensional (1-D) global motion task, but no difference was found on a static global form task. However, our results extend those of previous studies by demonstrating that poor readers exhibited impaired performance on a temporally-defined global form task, a finding that is difficult to reconcile with the dorsal stream vulnerability hypothesis. This suggests that the visual deficit in developmental dyslexia does not reflect an impairment detecting motion per se. It is better characterised as a difficulty processing temporal information, which is exacerbated when local visual cues have to be integrated across multiple (>2) dimensions.

The effect of magnocellular-based visual-motor intervention on Chinese children with developmental dyslexia

Magnocellular (M) deficit theory points out that the core deficit of developmental dyslexia (DD) is the impairment in M pathway, which has been evidenced in many previous studies. Based on the M deficit, some researchers found that visual intervention focusing on M deficit improved dyslexics’ M function as well as reading abilities. However, the number and reliability of these training studies were limited. Therefore, the present study conducted an M-based visual-motor intervention on Chinese children with DD to investigate the relationship between M deficit and Chinese DD. Intervention programs included coherent motion detection, visual search, visual tracking, and juggling, which were related to M function. The results showed that M function and phonological awareness of training dyslexic group were improved to a normal level as age-matched normal children after intervention, while non-training dyslexics did not. It supported M deficit theory, and suggested M deficit might be the core deficit of Chinese DD.

Magnocellular-dorsal pathway function is associated with orthographic but not phonological skill: fMRI evidence from skilled Chinese readers

Numerous studies have shown that magnocellular-dorsal (MD) pathway function is highly associated with reading ability, which is mostly indexed by phonological skill in alphabetic languages. However, it is less clear how MD pathway function influences phonological skill. As a logographic language, Chinese does not follow grapheme-phoneme correspondence rules, and thus provides a tool for delineating the effects of orthographic and phonological processing on reading. The current study used functional magnetic resonance imaging (fMRI) to measure MD pathway function in a coherent motion detection task for readers skilled in Chinese. A series of tests was used to assess participants' reading abilities, including orthographic and phonological processing skills. Results showed that several cortical regions of the MD pathway, including bilateral middle temporal visual motion areas (MT+) and the right posterior parietal cortex (PPC), were activated during the coherent motion detection task. Moreover, the activation was positively correlated with rapid naming speed, and greater activation in the left MT+ was associated with superior fluency and reduced accuracy in reading, suggesting that this pathway is also involved in modulating the speed of visual processing during reading. The most important finding was that activation of the right PPC was associated with orthographic awareness, but MD pathway activation was not related to phonological awareness. The results suggest that the MD pathway is highly associated with orthographic processing, which in turn influences more general aspects of reading skill.

The need to differentiate the magnocellular system from the dorsal stream in connection with dyslexia

A number of authors have postulated a "magnocellular-dorsal stream" deficit in dyslexia. Combining the magnocellular system and the dorsal stream into a single entity in this context faces the problem that contrast sensitivity data do not point to a magnocellular deficiency linked to dyslexia, while, on the other hand, motion perception data are largely consistent with a dorsal stream dysfunction. Thus, there are data both for and against a "magnocellular-dorsal stream" deficit in connection with dyslexia. It is here pointed out that this inconsistency is abolished once it is recognized that the magnocellular system and the dorsal stream are separate entities.

Speed discrimination predicts word but not pseudo-word reading rate in adults and children

Visual processing in the magnocellular pathway is a reputed influence on word recognition and reading performance. However, the mechanisms behind this relationship are still unclear. To explore this concept, we measured reading rate, speed-discrimination, and contrast detection thresholds in adults and children with a wide range of reading abilities. We found that speed discrimination thresholds are higher in children than in adults and are correlated with age. Speed discrimination thresholds are also correlated with reading rates but only for real words, not pseudo-words. Conversely, we found no correlations between contrast detection thresholds and the reading rates. We also found no correlations between speed discrimination or contrast detection and WASI subtest scores. These findings indicate that familiarity is a factor in magnocellular operations that may influence reading rate. We suggest this effect supports the idea that the magnocellular pathway contributes to word reading through an analysis of letter position.

The visual magnocellular deficit in Chinese-speaking children with developmental dyslexia

Many alphabetic studies have evidenced that individuals with developmental dyslexia (DD) have deficits in visual magnocellular (M) pathway. However, there are few studies to investigate the M function of Chinese DD. Chinese is a logographic language, and Chinese characters are complicated in structure. Visual skills and orthographic processing abilities are particularly important for efficient reading in Chinese as compared to alphabetic languages. Therefore, it is necessary to investigate the visual M function of Chinese DD and whether the M function was associated with orthographic skills. In the present study, 26 dyslexic children (mean age: 10.03 years) and 27 age-matched normal children (mean age: 10.37 years) took part in a coherent motion (CM) detection task and an orthographic awareness test. The results showed that dyslexic children had a significantly higher threshold than age-matched children in CM detection task. Meanwhile, children with DD responded more slowly in orthographic awareness test, although the group difference was marginally significant. The results suggested that Chinese dyslexics had deficits both in visual M pathway processing and orthographic processing. In order to investigate the relationship between M function and orthographic skills, we made a correlation analysis between CM threshold and orthographic awareness by merging performance of dyslexic children and age-matched children. The results revealed that CM thresholds were positively correlated with reaction times in orthographic awareness test, suggesting that better M function was related to better orthographic processing skills.

Development of sampling efficiency and internal noise in motion detection and discrimination in school-aged children

The aim of this study was to use an equivalent noise paradigm to investigate the development and maturation of motion perception, and how the underlying limitations of sampling efficiency and internal noise effect motion detection and direction discrimination in school-aged children (5-14 years) and adults. Contrast energy thresholds of a 2c/deg sinusoidal grating drifting at 1.0 or 6.0 Hz were measured as a function of added dynamic noise in three tasks: detection of a drifting grating; detection of the sum of two oppositely drifting gratings and direction discrimination of oppositely drifting gratings. Compared to the ideal observer, in both children and adults, the performance for all tasks was limited by reduced sampling efficiency and internal noise. However, the thresholds for discrimination of motion direction and detection of moving gratings show very different developmental profiles. Motion direction discrimination continues to improve after the age of 14 years due to an increase in sampling efficiency that differs with speed. Motion detection and summation were already mature at the age of 5 years, and internal noise was the same for all tasks. These findings were confirmed in a 1-year follow-up study on a group of children from the initial study. The results support suggestions that the detection of a moving pattern and discriminating motion direction are processed by different systems that may develop at different rates.

Global motion perception in 2-year-old children: a method for psychophysical assessment and relationships with clinical measures of visual function

PURPOSE

We developed and validated a technique for measuring global motion perception in 2-year-old children, and assessed the relationship between global motion perception and other measures of visual function.

METHODS

Random dot kinematogram (RDK) stimuli were used to measure motion coherence thresholds in 366 children at risk of neurodevelopmental problems at 24 ± 1 months of age. RDKs of variable coherence were presented and eye movements were analyzed offline to grade the direction of the optokinetic reflex (OKR) for each trial. Motion coherence thresholds were calculated by fitting psychometric functions to the resulting datasets. Test-retest reliability was assessed in 15 children, and motion coherence thresholds were measured in a group of 10 adults using OKR and behavioral responses. Standard age-appropriate optometric tests also were performed.

RESULTS

Motion coherence thresholds were measured successfully in 336 (91.8%) children using the OKR technique, but only 31 (8.5%) using behavioral responses. The mean threshold was 41.7 ± 13.5% for 2-year-old children and 3.3 ± 1.2% for adults. Within-assessor reliability and test-retest reliability were high in children. Children's motion coherence thresholds were significantly correlated with stereoacuity (LANG I & II test, ρ = 0.29, P < 0.001; Frisby, ρ = 0.17, P = 0.022), but not with binocular visual acuity (ρ = 0.11, P = 0.07). In adults OKR and behavioral motion coherence thresholds were highly correlated (intraclass correlation = 0.81, P = 0.001).

CONCLUSIONS

Global motion perception can be measured in 2-year-old children using the OKR. This technique is reliable and data from adults suggest that motion coherence thresholds based on the OKR are related to motion perception. Global motion perception was related to stereoacuity in children.

Why do adults with dyslexia have poor global motion sensitivity?

Two experiments aimed to determine why adults with dyslexia have higher global motion thresholds than typically reading controls. In Experiment 1, the dot density and number of animation frames presented in the dot stimulus were manipulated because of findings that use of a high dot density can normalize coherence thresholds in individuals with dyslexia. Dot densities were 14.15 and 3.54 dots/deg². These were presented for five (84 ms) or eight (134 ms) frames. The dyslexia group had higher coherence thresholds in all conditions than controls. However, in the high dot density, long duration condition, both reader groups had the lowest thresholds indicating normal temporal recruitment. These results indicated that the dyslexia group could sample the additional signals dots over space and then integrate these with the same efficiency as controls. In Experiment 2, we determined whether briefly presenting a fully coherent prime moving in either the same or opposite direction of motion to a partially coherent test stimulus would systematically increase and decrease global motion thresholds in the reader groups. When the direction of motion in the prime and test was the same, global motion thresholds increased for both reader groups. The increase in coherence thresholds was significantly greater for the dyslexia group. When the motion of the prime and test were presented in opposite directions, coherence thresholds were reduced in both groups. No group threshold differences were found. We concluded that the global motion processing deficit found in adults with dyslexia can be explained by undersampling of the target motion signals. This might occur because of difficulties directing attention to the relevant motion signals in the random dot pattern, and not a specific difficulty integrating global motion signals. These effects are most likely to occur in the group with dyslexia when more complex computational processes are required to process global motion.

Probing the neurocognitive trajectories of children's reading skills

Emerging evidence of the high variability in the cognitive skills and deficits associated with reading achievement and dysfunction promotes both a more dimensional view of the risk factors involved, and the importance of discriminating between trajectories of impairment. Here we examined reading and component orthographic and phonological skills alongside measures of cognitive ability and auditory and visual sensory processing in a large group of primary school children between the ages of 7 and 12 years. We identified clusters of children with pseudoword or exception word reading scores at the 10th percentile or below relative to their age group, and a group with poor skills on both tasks. Compared to age-matched and reading-level controls, groups of children with more impaired exception word reading were best described by a trajectory of developmental delay, whereas readers with more impaired pseudoword reading or combined deficits corresponded more with a pattern of atypical development. Sensory processing deficits clustered within both of the groups with putative atypical development: auditory discrimination deficits with poor phonological awareness skills; impairments of visual motion processing in readers with broader and more severe patterns of reading and cognitive impairments. Sensory deficits have been variably associated with developmental impairments of literacy and language; these results suggest that such deficits are also likely to cluster in children with particular patterns of reading difficulty.

Motion perception in children with foetal alcohol syndrome

AIM

To evaluate the visual magnocellular pathway by a coherent motion perception test in children with foetal alcohol syndrome (FAS).

METHODS

Eighty-nine children (49 with verified FAS and 40 without FAS) aged from 10 to 16 years were included into the study. Both the study and the control group were children living in orphanages. A coherent motion perception test was used. The test consisted of 150 white moving dots on a black background presented in different signal-to-noise ratio conditions. The task was direction detection of the coherently moving dots whose percentage decreased at each step.

RESULTS

A significant difference between the two groups was found (p = 0.018). Children with FAS had lower coherent motion perception ability in all the signal-to-noise ratio conditions. A significant difference between difficulty levels (p < 0.001) was found for all subjects in both groups - decreasing the stimulus signal-to-noise level decreased the motion perception score. In both groups, the motion perception score differed for vertical and horizontal stimuli (p = 0.003) with better performance with vertical stimuli.

CONCLUSION

Impaired motion perception in FAS children could be indicative of a dorsal stream developmental dysfunction resulting from alcohol brain damage.

Coherent motion sensitivity predicts individual differences in subtraction

Recent findings suggest deficits in coherent motion sensitivity, an index of visual dorsal stream functioning, in children with poor mathematical skills or dyscalculia, a specific learning disability in mathematics. We extended these data using a longitudinal design to unravel whether visual dorsal stream functioning is able to predict individual differences in subsequent specific mathematical skills, i.e., single-digit subtraction and multiplication. We measured children's sensitivity to coherent motion in kindergarten (mean age: 5 years 8 months) and evaluated their subtraction and multiplication skills in third grade (mean age 8 years 3 months). Findings revealed an association between subtraction but not multiplication performance and coherent motion sensitivity. This association remained significant even when intellectual ability and reading ability were additionally controlled for. Subtractions are typically solved by means of quantity-based procedural strategies, which reliably recruit the intraparietal sulcus. Against the background of a neural overlap between the intraparietal sulcus and visual dorsal stream functioning, we hypothesize that low-level visuospatial mechanisms might set constraints on the development of quantity representations, which are used during calculation, particularly in subtraction.