Action video games and posterior parietal cortex neuromodulation enhance both attention and reading in adults with developmental dyslexia.

The impact of action video games on reading performance has been already demonstrated in individuals with and without neurodevelopmental disorders. The combination of action video games and posterior parietal cortex neuromodulation by a transcranial random noise stimulation could enhance brain plasticity, improving attentional control and reading skills also in adults with developmental dyslexia. In a double blind randomized controlled trial, 20 young adult nonaction video game players with developmental dyslexia were trained for 15 h with action video games. Half of the participants were stimulated with bilateral transcranial random noise stimulation on the posterior parietal cortex during the action video game training, whereas the others were in the placebo (i.e. sham) condition. Word text reading, pseudowords decoding, and temporal attention (attentional blink), as well as electroencephalographic activity during the attentional blink, were measured before and after the training. The action video game + transcranial random noise stimulation group showed temporal attention, word text reading, and pseudoword decoding enhancements and P300 amplitude brain potential changes. The enhancement in temporal attention performance was related with the efficiency in pseudoword decoding improvement. Our results demonstrate that the combination of action video game training with parietal neuromodulation increases the efficiency of visual attention deployment, probably reshaping goal-directed and stimulus-driven fronto-parietal attentional networks interplay in young adults with neurodevelopmental conditions.

Infants' reorienting efficiency depends on parental autistic traits and predicts future socio-communicative behaviors.

Attentional reorienting is dysfunctional not only in children with autism spectrum disorder (ASD), but also in infants who will develop ASD, thus constituting a potential causal factor of future social interaction and communication abilities. Following the research domain criteria framework, we hypothesized that the presence of subclinical autistic traits in parents should lead to atypical infants' attentional reorienting, which in turn should impact on their future socio-communication behavior in toddlerhood. During an attentional cueing task, we measured the saccadic latencies in a large sample (total enrolled n = 89; final sample n = 71) of 8-month-old infants from the general population as a proxy for their stimulus-driven attention. Infants were grouped in a high parental traits (HPT; n = 23) or in a low parental traits (LPT; n = 48) group, according to the degree of autistic traits self-reported by their parents. Infants (n = 33) were then longitudinally followed to test their socio-communicative behaviors at 21 months. Results show a sluggish reorienting system, which was a longitudinal predictor of future socio-communicative skills at 21 months. Our combined transgenerational and longitudinal findings suggest that the early functionality of the stimulus-driven attentional network-redirecting attention from one event to another-could be directly connected to future social and communication development.

Local perception impairs the lexical reading route.

Human perception of a visual scene is hierarchically organized. Such rapid, albeit coarse, global processing allows people to create a useful context in which local details can be successively allocated. Lack of the typical hierarchical global-to-local visual processing is longitudinally predictive of future reading difficulties in pre-readers, which suggests that an atypical local perception can interfere with reading skill acquisition. Global and local Navon tasks were used to induce a transient perceptual priming before a reading-aloud task. We tested the effect of an atypical local perception on lexical and sublexical reading routes in typical adult readers. Local (vs. global) priming resulted in a slower phonological access to irregular, relative to regular, words. By contrast, pseudoword reading was not affected by local (vs. global) perceptual priming. Our findings demonstrate that, in typical adult readers, local priming impairs the fast processing of the letter string useful for lexical reading.

Multiple Causal Links Between Magnocellular-Dorsal Pathway Deficit and Developmental Dyslexia.

Although impaired auditory-phonological processing is the most popular explanation of developmental dyslexia (DD), the literature shows that the combination of several causes rather than a single factor contributes to DD. Functioning of the visual magnocellular-dorsal (MD) pathway, which plays a key role in motion perception, is a much debated, but heavily suspected factor contributing to DD. Here, we employ a comprehensive approach that incorporates all the accepted methods required to test the relationship between the MD pathway dysfunction and DD. The results of 4 experiments show that (1) Motion perception is impaired in children with dyslexia in comparison both with age-match and with reading-level controls; (2) pre-reading visual motion perception-independently from auditory-phonological skill-predicts future reading development, and (3) targeted MD trainings-not involving any auditory-phonological stimulation-leads to improved reading skill in children and adults with DD. Our findings demonstrate, for the first time, a causal relationship between MD deficits and DD, virtually closing a 30-year long debate. Since MD dysfunction can be diagnosed much earlier than reading and language disorders, our findings pave the way for low resource-intensive, early prevention programs that could drastically reduce the incidence of DD.

The attentional 'zoom-lens' in 8-month-old infants.

The spatial attention mechanisms of orienting and zooming cooperate to properly select visual information from the environment and plan eye movements accordingly. Despite the fact that orienting ability has been extensively studied in infancy, the zooming mechanism--namely, the ability to distribute the attentional resources to a small or large portion of the visual field--has never been tested before. The aim of the present study was to evaluate the attentional zooming abilities of 8-month-old infants. An eye-tracker device was employed to measure the saccadic latencies (SLs) at the onset of a visual target displayed at two eccentricities. The size of the more eccentric target was adjusted in order to counteract the effect of cortical magnification. Before the target display, attentional resources were automatically focused (zoom-in) or spread out (zoom-out) by using a small or large cue, respectively. Two different cue-target intervals were also employed to measure the time course of this attentional mechanism. The results showed that infants' SLs varied as a function of the cue size. Moreover, a clear time course emerged, demonstrating that infants can rapidly adjust the attentional focus size during a pre-saccadic temporal window. These findings could serve as an early marker for neurodevelopmental disorders associated with attentional zooming dysfunction such as autism and dyslexia.

The DCDC2 intron 2 deletion impairs illusory motion perception unveiling the selective role of magnocellular-dorsal stream in reading (dis)ability.

Developmental dyslexia (DD) is a heritable neurodevelopmental reading disorder that could arise from auditory, visual, and cross-modal integration deficits. A deletion in intron 2 of the DCDC2 gene (hereafter DCDC2d) increases the risk for DD and related phenotypes. In this study, first we report that illusory visual motion perception-specifically processed by the magnocellular-dorsal (M-D) stream-is impaired in children with DD compared with age-matched and reading-level controls. Second, we test for the specificity of the DCDC2d effects on the M-D stream. Children with DD and DCDC2d need significantly more contrast to process illusory motion relative to their counterpart without DCDC2d and to age-matched and reading-level controls. Irrespective of the genetic variant, children with DD perform normally in the parvocellular-ventral task. Finally, we find that DCDC2d is associated with the illusory motion perception also in adult normal readers, showing that the M-D deficit is a potential neurobiological risk factor of DD rather than a simple effect of reading disorder. Our findings demonstrate, for the first time, that a specific neurocognitive dysfunction tapping the M-D stream is linked with a well-defined genetic susceptibility.

Do rhesus monkeys (Macaca mulatta) perceive illusory motion?

During the last decade, visual illusions have been used repeatedly to understand similarities and differences in visual perception of human and non-human animals. However, nearly all studies have focused only on illusions not related to motion perception, and to date, it is unknown whether non-human primates perceive any kind of motion illusion. In the present study, we investigated whether rhesus monkeys (Macaca mulatta) perceived one of the most popular motion illusions in humans, the Rotating Snake illusion (RSI). To this purpose, we set up four experiments. In Experiment 1, subjects initially were trained to discriminate static versus dynamic arrays. Once reaching the learning criterion, they underwent probe trials in which we presented the RSI and a control stimulus identical in overall configuration with the exception that the order of the luminance sequence was changed in a way that no apparent motion is perceived by humans. The overall performance of monkeys indicated that they spontaneously classified RSI as a dynamic array. Subsequently, we tested adult humans in the same task with the aim of directly comparing the performance of human and non-human primates (Experiment 2). In Experiment 3, we found that monkeys can be successfully trained to discriminate between the RSI and a control stimulus. Experiment 4 showed that a simple change in luminance sequence in the two arrays could not explain the performance reported in Experiment 3. These results suggest that some rhesus monkeys display a human-like perception of this motion illusion, raising the possibility that the neurocognitive systems underlying motion perception may be similar between human and non-human primates.

TMS on right frontal eye fields induces an inflexible focus of attention.

The focus of spatial attention can be not only oriented to a particular location, but also adjusted in its size to select visual information from a narrow (zoom-in) or broad (zoom-out) region of the visual field. Attentional orienting, saccades programming, and visual search have been linked to the frontal eye fields (FEF) activity. However, the FEF causal role in the frontoparietal network for the attentional focus size modulation remains unclear. Here, we delivered single-pulse transcranial magnetic stimulation (TMS) on FEF while participants performed an attentional zooming task. They were asked to detect a visual target appearing at 3 eccentricities from the fixation. Two cue types modulated the size of the attended region: a small cue was employed to narrow the attentional focus, whereas a large cue induced participants to broaden the attended region. Results showed that TMS delivered on the right FEF, but not on the left FEF, was able to interfere with both zoom-in and zoom-out attentional mechanisms. Our results provide the first evidence of the right FEF casual role in the attentional zooming control and give new insights into the neural mechanisms of dysfunctional spatial attention deployment shown in neurodevelopmental disorders, such as autism and dyslexia.

How the visual aspects can be crucial in reading acquisition? The intriguing case of crowding and developmental dyslexia.

Developmental dyslexia (DD) is the most common neurodevelopmental disorder (about 10% of children across cultures) characterized by severe difficulties in learning to read. According to the dominant view, DD is considered a phonological processing impairment that might be linked to a cross-modal, letter-to-speech sound integration deficit. However, new theories-supported by consistent data-suggest that mild deficits in low-level visual and auditory processing can lead to DD. This evidence supports the probabilistic and multifactorial approach for DD. Among others, an interesting visual deficit that is often associated with DD is excessive visual crowding. Crowding is defined as difficulty in the ability to recognize objects when surrounded by similar items. Crowding, typically observed in peripheral vision, could be modulated by attentional processes. The direct consequence of stronger crowding on reading is the inability to recognize letters when they are surrounded by other letters. This problem directly translates to reading at a slower speed and being more prone to making errors while reading. Our aim is to review the literature supporting the important role of crowding in DD. Moreover, we are interested in proposing new possible studies in order to clarify whether the observed excessive crowding could be a cause rather than an effect of DD. Finally, we also suggest possible remediation and even prevention programs that could be based on reducing the crowding in children with or at risk for DD without involving any phonological or orthographic training.

Action video games normalise the phonemic awareness in pre-readers at risk for developmental dyslexia.

Action video-games (AVGs) could improve reading efficiency, enhancing not only visual attention but also phonological processing. Here we tested the AVG effects upon three consolidated language-based predictors of reading development in a sample of 79 pre-readers at-risk and 41 non-at-risk for developmental dyslexia. At-risk children were impaired in either phonemic awareness (i.e., phoneme discrimination task), phonological working memory (i.e., pseudoword repetition task) or rapid automatized naming (i.e., RAN of colours task). At-risk children were assigned to different groups by using an unequal allocation randomization: (1) AVG (n = 43), (2) Serious Non-Action Video Game (n = 11), (3) treatment-as-usual (i.e., speech therapy, n = 11), and (4) waiting list (n = 14). Pre- and post-training comparisons show that only phonemic awareness has a significantly higher improvement in the AVG group compared to the waiting list, the non-AVG, and the treatment-as-usual groups, as well as the combined active groups (n = 22). This cross-modal plastic change: (i) leads to a recovery in phonemic awareness when compared to the not-at-risk pre-readers; (ii) is present in more than 80% of AVG at-risk pre-readers, and; (iii) is maintained at a 6-months follow-up. The present findings indicate that this specific multisensory attentional training positively affects how phonemic awareness develops in pre-readers at risk for developmental dyslexia, paving the way for innovative prevention programs.

Deeper attentional masking by lateral objects in children with autism.

Autism spectrum disorder (ASD) is often associated with a detail-oriented perception and overselective attention in visual tasks, such as visual search and crowding. These results were obtained manipulating exclusively the spatial properties of the stimuli: few is known about the spatio-temporal dynamics of visual processing in ASD. In this study we employed an attentional masking (AM) paradigm comparing children with ASD and IQ-matched typically developing (TD) controls. The AM effect refers to an impaired identification of a target followed by a competitive masking object at different proximities in space and time. We found that ASD and TD groups did not differ in the AM effect provoked by the competitive object displayed in the same position of the target. In contrast, children with ASD showed a deeper and prolonged interference than the TD group when the masking object was displayed in the lateral position. These psychophysical results suggest that the inefficient attentional selection in ASD depends on the spatio-temporal interaction between competitive visual objects. These evidence are discussed in the light of the ASD altered neural connectivity hypothesis and the reentrant theory of perception.

Visuo-spatial attention deficit in children with reading difficulties.

Although developmental reading disorders (developmental dyslexia) have been mainly associated with auditory-phonological deficits, recent longitudinal and training studies have shown a possible causal role of visuo-attentional skills in reading acquisition. Indeed, visuo-attentional mechanisms could be involved in the orthographic processing of the letter string and the graphemic parsing that precede the grapheme-to-phoneme mapping. Here, we used a simple paper-and-pencil task composed of three labyrinths to measure visuo-spatial attention in a large sample of primary school children (n = 398). In comparison to visual search tasks requiring visual working memory, our labyrinth task mainly measures distributed and focused visuo-spatial attention, also controlling for sensorimotor learning. Compared to typical readers (n = 340), children with reading difficulties (n = 58) showed clear visuo-spatial attention impairments that appear not linked to motor coordination and procedural learning skills implicated in this paper and pencil task. Since visual attention is dysfunctional in about 40% of the children with reading difficulties, an efficient reading remediation program should integrate both auditory-phonological and visuo-attentional interventions.

Action Video Games Enhance Attentional Control and Phonological Decoding in Children with Developmental Dyslexia.

Reading acquisition is extremely difficult for about 5% of children because they are affected by a heritable neurobiological disorder called developmental dyslexia (DD). Intervention studies can be used to investigate the causal role of neurocognitive deficits in DD. Recently, it has been proposed that action video games (AVGs)-enhancing attentional control-could improve perception and working memory as well as reading skills. In a partial crossover intervention study, we investigated the effect of AVG and non-AVG training on attentional control using a conjunction visual search task in children with DD. We also measured the non-alphanumeric rapid automatized naming (RAN), phonological decoding and word reading before and after AVG and non-AVG training. After both video game training sessions no effect was found in non-alphanumeric RAN and in word reading performance. However, after only 12 h of AVG training the attentional control was improved (i.e., the set-size slopes were flatter in visual search) and phonological decoding speed was accelerated. Crucially, attentional control and phonological decoding speed were increased only in DD children whose video game score was highly efficient after the AVG training. We demonstrated that only an efficient AVG training induces a plasticity of the fronto-parietal attentional control linked to a selective phonological decoding improvement in children with DD.

Beyond Reading Modulation: Temporo-Parietal tDCS Alters Visuo-Spatial Attention and Motion Perception in Dyslexia.

Dyslexia is a neurodevelopmental disorder with an atypical activation of posterior left-hemisphere brain reading networks (i.e., temporo-occipital and temporo-parietal regions) and multiple neuropsychological deficits. Transcranial direct current stimulation (tDCS) is a tool for manipulating neural activity and, in turn, neurocognitive processes. While studies have demonstrated the significant effects of tDCS on reading, neurocognitive changes beyond reading modulation have been poorly investigated. The present study aimed at examining whether tDCS on temporo-parietal regions affected not only reading, but also phonological skills, visuo-spatial working memory, visuo-spatial attention, and motion perception in a polarity-dependent way. In a within-subjects design, ten children and adolescents with dyslexia performed reading and neuropsychological tasks after 20 min of exposure to Left Anodal/Right Cathodal (LA/RC) and Right Anodal/Left Cathodal (RA/LC) tDCS. LA/RC tDCS compared to RA/LC tDCS improved text accuracy, word recognition speed, motion perception, and modified attentional focusing in our group of children and adolescents with dyslexia. Changes in text reading accuracy and word recognition speed-after LA/RC tDCS compared to RA/LC-were related to changes in motion perception and in visuo-spatial working memory, respectively. Our findings demonstrated that reading and domain-general neurocognitive functions in a group of children and adolescents with dyslexia change following tDCS and that they are polarity-dependent.

Visual spatial attention and speech segmentation are both impaired in preschoolers at familial risk for developmental dyslexia.

Phonological skills are foundational of reading acquisition and impaired phonological processing is widely assumed to characterize dyslexic individuals. However, reading by phonological decoding also requires rapid selection of sublexical orthographic units through serial attentional orienting, and recent studies have shown that visual spatial attention is impaired in dyslexic children. Our study investigated these different neurocognitive dysfunctions, before reading acquisition, in a sample of preschoolers including children with (N=20) and without (N=67) familial risk for developmental dyslexia. Children were tested on phonological skills, rapid automatized naming, and visual spatial attention. At-risk children presented deficits in both visual spatial attention and syllabic segmentation at the group level. Moreover, the combination of visual spatial attention and syllabic segmentation scores was more reliable than either single measure for the identification of at-risk children. These findings suggest that both visuo-attentional and perisylvian-auditory dysfunctions might adversely affect reading acquisition, and may offer a new approach for early identification and remediation of developmental dyslexia.

Caffeine improves text reading and global perception.

BACKGROUND: Reading is a unique human skill. Several brain networks involved in this complex skill mainly involve the left hemisphere language areas. Nevertheless, nonlinguistic networks found in the right hemisphere also seem to be involved in sentence and text reading. These areas do not deal with phonological information, but are involved in verbal and nonverbal pattern information processing. The right hemisphere is responsible for global processing of a scene, which is needed for developing reading skills. AIMS: Caffeine seems to affect global pattern processing specifically. Consequently, our aim was to discover if it could enhance text reading skill. METHODS: In two mechanistic studies (n=24 and n=53), we tested several reading skills, global and local perception, alerting, spatial attention and executive functions, as well as rapid automatised naming and phonological memory, using a double-blind, within-subjects, repeated-measures design in typical young adult readers. RESULTS: A single dose of 200 mg caffeine improved global processing, without any effect on local information processing, alerting, spatial attention and executive or phonological functions. This improvement in global processing was accompanied by faster text reading speed of meaningful sentences, whereas single word/pseudoword or pseudoword text reading abilities were not affected. These effects of caffeine on reading ability were enhanced by mild sleep deprivation. CONCLUSIONS: These findings show that a small quantity of caffeine could improve global processing and text reading skills in adults.

The Mediation Role of Dynamic Multisensory Processing Using Molecular Genetic Data in Dyslexia.

Although substantial heritability has been reported and candidate genes have been identified, we are far from understanding the etiopathogenetic pathways underlying developmental dyslexia (DD). Reading-related endophenotypes (EPs) have been established. Until now it was unknown whether they mediated the pathway from gene to reading (dis)ability. Thus, in a sample of 223 siblings from nuclear families with DD and 79 unrelated typical readers, we tested four EPs (i.e., rapid auditory processing, rapid automatized naming, multisensory nonspatial attention and visual motion processing) and 20 markers spanning five DD-candidate genes (i.e., DYX1C1, DCDC2, KIAA0319, ROBO1 and GRIN2B) using a multiple-predictor/multiple-mediator framework. Our results show that rapid auditory and visual motion processing are mediators in the pathway from ROBO1-rs9853895 to reading. Specifically, the T/T genotype group predicts impairments in rapid auditory and visual motion processing which, in turn, predict poorer reading skills. Our results suggest that ROBO1 is related to reading via multisensory temporal processing. These findings support the use of EPs as an effective approach to disentangling the complex pathways between candidate genes and behavior.

Is excessive visual crowding causally linked to developmental dyslexia?

For about 10% of children reading acquisition is extremely difficult because they are affected by a heritable neurobiological disorder called developmental dyslexia (DD), mainly associated to an auditory-phonological disorder. Visual crowding is a universal phenomenon that impairs the recognition of stimuli in clutter, such as a letter in a word or a word in a text. Several studies have shown an excessive crowding in individuals with DD, but the causal link between excessive crowding and DD is not yet clearly established. An excessive crowding might be, indeed, a simple effect of DD due to reduced reading experience. The results of five experiments in 181 children reveal that: (i) an excessive crowding only at unattended locations characterizes an unselected group of children with DD (Experiment 1); (ii) an extra-large spaced text increases reading accuracy by reducing crowding in an unselected group of children with DD (Experiment 2); (iii) efficient attentional action video game trainings reduce crowding and accelerate reading speed in two unselected groups of children with DD (Experiment 3 and 4), and; (iv) pre-reading crowding longitudinally predicts future poor readers (Experiment 5). Our results show multiple causal links between visual crowding and learning to read. These findings provide new insights for a more efficient remediation and prevention for DD.

A new psychophysical estimation of the receptive field size.

When a line extends beyond the width of an aperture, its direction of motion cannot be detected correctly. Only the component of motion perpendicular to the line is detectable (aperture problem). Early visual areas face the same aperture problem because receptive field sizes are relatively small. The susceptibility of early visual areas to the aperture problem opens an opportunity to measure the aperture width of a receptive field psychophysically that can be used to estimate the receptive field size. We found an already established visual illusion (the rotating tilted lines illusion or RTLI) can be used to measure the aperture size and hence estimate the receptive field size. To estimate the receptive field size, we conducted a psychophysical experiment in which the radii and tilted line length of RTLI were systematically changed. Our psychophysical estimation of receptive field size strongly corresponds with the previous measures of receptive field size using electrophysiological and fMRI methods.

Brief Report: When Large Becomes Slow: Zooming-Out Visual Attention Is Associated to Orienting Deficits in Autism.

Previous studies independently demonstrated impairments in rapid orienting/disengagement and zooming-out of spatial attention in autism spectrum disorder (ASD). These attentional mechanisms, however, are not completely independent. Aiming at a more complete picture of spatial attention deficits in ASD, we examined the relationship between orienting and zooming in participants with ASD and typically developing peers. We modified a classical spatial cuing task, presenting two small or large cues in the two visual hemifields and subsequently cueing attention to one of them. Our results demonstrate a sluggish orienting mechanism in ASD only when a large attentional focus is deployed. Moreover, only the sluggish orienting mechanism in the large cues condition predicts the severity in the social-interaction symptomatology in individuals with ASD.