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Lawton T, Shelley-Tremblay J, Huang MX. Case report: Neural timing deficits prevalent in developmental disorders, aging, and concussions remediated rapidly by movement discrimination exercises. Front Neurol 2023; 14:898781. [PMID: 37818220 PMCID: PMC10560731 DOI: 10.3389/fneur.2023.898781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 09/04/2023] [Indexed: 10/12/2023] Open
Abstract
Background The substantial evidence that neural timing deficits are prevalent in developmental disorders, aging, and concussions resulting from a Traumatic Brain Injury (TBI) is presented. Objective When these timing deficits are remediated using low-level movement-discrimination training, then high-level cognitive skills, including reading, attention, processing speed, problem solving, and working memory improve rapidly and effectively. Methods In addition to the substantial evidence published previously, new evidence based on a neural correlate, MagnetoEncephalography physiological recordings, on an adult dyslexic, and neuropsychological tests on this dyslexic subject and an older adult were measured before and after 8-weeks of contrast sensitivity-based left-right movement-discrimination exercises were completed. Results The neuropsychological tests found large improvements in reading, selective and sustained attention, processing speed, working memory, and problem-solving skills, never before found after such a short period of training. Moreover, these improvements were found 4 years later for older adult. Substantial MEG signal increases in visual Motion, Attention, and Memory/Executive Control Networks were observed following training on contrast sensitivity-based left-right movement-discrimination. Improving the function of magnocells using figure/ground movement-discrimination at both low and high levels in dorsal stream: (1) improved both feedforward and feedback pathways to modulate attention by enhancing coupled theta/gamma and alpha/gamma oscillations, (2) is adaptive, and (3) incorporated cycles of feedback and reward at multiple levels. Conclusion What emerges from multiple studies is the essential role of timing deficits in the dorsal stream that are prevalent in developmental disorders like dyslexia, in aging, and following a TBI. Training visual dorsal stream function at low levels significantly improved high-level cognitive functions, including processing speed, selective and sustained attention, both auditory and visual working memory, problem solving, and reading fluency. A paradigm shift for treating cognitive impairments in developmental disorders, aging, and concussions is crucial. Remediating the neural timing deficits of low-level dorsal pathways, thereby improving both feedforward and feedback pathways, before cognitive exercises to improve specific cognitive skills provides the most rapid and effective methods to improve cognitive skills. Moreover, this adaptive training with substantial feedback shows cognitive transfer to tasks not trained on, significantly improving a person's quality of life rapidly and effectively.
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Affiliation(s)
- Teri Lawton
- Cognitive Neuroscience, Perception Dynamics Institute, Encinitas, CA, United States
| | | | - Ming-Xiong Huang
- Radiology Imaging Laboratory, Department of Radiology, University of California, San Diego, San Diego, CA, United States
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2
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Oishi H, Takemura H, Amano K. Macromolecular tissue volume mapping of lateral geniculate nucleus subdivisions in living human brains. Neuroimage 2023; 265:119777. [PMID: 36462730 DOI: 10.1016/j.neuroimage.2022.119777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 11/26/2022] [Accepted: 11/29/2022] [Indexed: 12/03/2022] Open
Abstract
The lateral geniculate nucleus (LGN) is a key thalamic nucleus in the visual system, which has an important function in relaying retinal visual input to the visual cortex. The human LGN is composed mainly of magnocellular (M) and parvocellular (P) subdivisions, each of which has different stimulus selectivity in neural response properties. Previous studies have discussed the potential relationship between LGN subdivisions and visual disorders based on psychophysical data on specific types of visual stimuli. However, these relationships remain speculative because non-invasive measurements of these subdivisions are difficult due to the small size of the LGN. Here we propose a method to identify these subdivisions by combining two structural MR measures: high-resolution proton-density weighted images and macromolecular tissue volume (MTV) maps. We defined the M and P subdivisions based on MTV fraction data and tested the validity of the definition by (1) comparing the data with that from human histological studies, (2) comparing the data with functional magnetic resonance imaging measurements on stimulus selectivity, and (3) analyzing the test-retest reliability. The findings demonstrated that the spatial organization of the M and P subdivisions was consistent across subjects and in line with LGN subdivisions observed in human histological data. Moreover, the difference in stimulus selectivity between the subdivisions identified using MTV was consistent with previous physiology literature. The definition of the subdivisions based on MTV was shown to be robust over measurements taken on different days. These results suggest that MTV mapping is a promising approach for evaluating the tissue properties of LGN subdivisions in living humans. This method potentially will enable neuroscientific and clinical hypotheses about the human LGN subdivisions to be tested.
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Affiliation(s)
- Hiroki Oishi
- Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology, Suita 565-0871, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan; Department of Psychology, University of California, Berkeley, Berkeley, CA 94704, United States.
| | - Hiromasa Takemura
- Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology, Suita 565-0871, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan; Division of Sensory and Cognitive Brain Mapping, Department of System Neuroscience, National Institute for Physiological Sciences, Okazaki 444-8585, Japan; Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193, Japan.
| | - Kaoru Amano
- Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology, Suita 565-0871, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan; Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 113-8656, Japan
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3
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Stein J. The visual basis of reading and reading difficulties. Front Neurosci 2022; 16:1004027. [PMID: 36507333 PMCID: PMC9728103 DOI: 10.3389/fnins.2022.1004027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 09/16/2022] [Indexed: 11/24/2022] Open
Abstract
Most of our knowledge about the neural networks mediating reading has derived from studies of developmental dyslexia (DD). For much of the 20th C. this was diagnosed on the basis of finding a discrepancy between children's unexpectedly low reading and spelling scores compared with their normal or high oral and non-verbal reasoning ability. This discrepancy criterion has now been replaced by the claim that the main feature of dyslexia is a phonological deficit, and it is now argued that we should test for this to identify dyslexia. However, grasping the phonological principle is essential for all learning to read; so every poor reader will show a phonological deficit. The phonological theory does not explain why dyslexic people, in particular, fail; so this phonological criterion makes it impossible to distinguish DD from any of the many other causes of reading failure. Currently therefore, there is no agreement about precisely how we should identify it. Yet, if we understood the specific neural pathways that underlie failure to acquire phonological skills specifically in people with dyslexia, we should be able to develop reliable means of identifying it. An important, though not the only, cause in people with dyslexia is impaired development of the brain's rapid visual temporal processing systems; these are required for sequencing the order of the letters in a word accurately. Such temporal, "transient," processing is carried out primarily by a distinct set of "magnocellular" (M-) neurones in the visual system; and the development of these has been found to be impaired in many people with dyslexia. Likewise, auditory sequencing of the sounds in a word is mediated by the auditory temporal processing system whose development is impaired in many dyslexics. Together these two deficits can therefore explain their problems with acquiring the phonological principle. Assessing poor readers' visual and auditory temporal processing skills should enable dyslexia to be reliably distinguished from other causes of reading failure and this will suggest principled ways of helping these children to learn to read, such as sensory training, yellow or blue filters or omega 3 fatty acid supplements. This will enable us to diagnose DD with confidence, and thus to develop educational plans targeted to exploit each individual child's strengths and compensate for his weaknesses.
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Meng ZL, Liu ML, Bi HY. Spatial and temporal processing difficulties in Chinese children with developmental dyslexia: An ERP study. DYSLEXIA (CHICHESTER, ENGLAND) 2022; 28:416-430. [PMID: 35918880 DOI: 10.1002/dys.1723] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Revised: 06/25/2022] [Accepted: 07/06/2022] [Indexed: 06/15/2023]
Abstract
Magnocellular (M) deficit theory indicates that individuals with developmental dyslexia (DD) have low sensitivity to stimuli with high temporal frequencies (HTF) and low spatial frequencies (LSF). However, some studies found that temporal processing and spatial processing were correlated with different reading-related skills. Chinese is a logographic language, and visual skills are particularly important for reading in Chinese. It is necessary to investigate the temporal and spatial processing abilities in the M pathway of Chinese children with DD. Using electrophysiological recordings, the present study examined the mean amplitude and latency of P1 during a grating direction judgment task in 13 children with DD and 13 age-matched normal children. Dyslexic children showed a low amplitude and long latency of P1 in the HTF condition and LSF condition compared with age-matched children. In the HTF condition, the amplitude of P1 correlated with phonological awareness, and the latency of P1 correlated with reading fluency and rapid naming of digits. The amplitude of P1 in the LSF condition correlated with reading accuracy. This result suggested that Chinese children with DD had difficulties in both temporal and spatial processing in the M pathway. However, temporal processing and spatial processing played different roles in Chinese reading.
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Affiliation(s)
- Ze-Long Meng
- CAS Key Laboratory of Behavioral Science, Center for Brain Science and Learning Difficulties, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
- Department of Psychology, School of Humanities and Social Sciences, Beijing Forestry University, Beijing, China
| | - Meng-Lian Liu
- CAS Key Laboratory of Behavioral Science, Center for Brain Science and Learning Difficulties, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Hong-Yan Bi
- CAS Key Laboratory of Behavioral Science, Center for Brain Science and Learning Difficulties, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
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Liu YF, Qian Y, Bi HY. Visual motion processing in Chinese children with developmental dyslexia: An fMRI study. DYSLEXIA (CHICHESTER, ENGLAND) 2022; 28:431-447. [PMID: 36329601 DOI: 10.1002/dys.1726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 06/30/2022] [Accepted: 07/21/2022] [Indexed: 06/16/2023]
Abstract
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.
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Affiliation(s)
- Yu-Fei Liu
- CAS Key Laboratory of Behavioral Science, Center for Brain Science and Learning Difficulties, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
- China Textile and Apparel Press, Beijing, China
| | - Yi Qian
- CAS Key Laboratory of Behavioral Science, Center for Brain Science and Learning Difficulties, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
- Wuxi Institute of Technology, Wuxi, China
| | - Hong-Yan Bi
- CAS Key Laboratory of Behavioral Science, Center for Brain Science and Learning Difficulties, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
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6
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Zhang J, Yang H, Li W, Li Y, Qin J, He L. Automatic Schizophrenia Detection Using Multimodality Media via a Text Reading Task. Front Neurosci 2022; 16:933049. [PMID: 35911987 PMCID: PMC9331283 DOI: 10.3389/fnins.2022.933049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 06/13/2022] [Indexed: 11/13/2022] Open
Abstract
Schizophrenia is a crippling chronic mental disease that affects people worldwide. In this work, an automatic schizophrenia detection algorithm is proposed based on the reading deficit of schizophrenic patients. From speech and video modalities, the automatic schizophrenia detection algorithm illustrates abnormal speech, head movement, and reading fluency during the reading task. In the speech modality, an acoustic model of speech emotional flatness in schizophrenia is established to reflect the emotional expression flatness of schizophrenic speech from the perspective of speech production and perception. In the video modality, the head-movement-related features are proposed to illustrate the spontaneous head movement caused by repeated reading and unconscious movement, and the reading-fluency-related features are proposed to convey the damaged degree of schizophrenic patients' reading fluency. The experimental data of this work are 160 segments of speech and video data recorded by 40 participants (20 schizophrenic patients and 20 normal controls). Combined with support vector machines and random forest, the accuracy of the proposed acoustic model, the head-movement-related features, and the reading-fluency-related features range from 94.38 to 96.50%, 73.38 to 83.38%, and 79.50 to 83.63%, respectively. The average accuracy of the proposed automatic schizophrenia detection algorithm reaches 97.50%. The experimental results indicate the effectiveness of the proposed automatic detection algorithm as an auxiliary diagnostic method for schizophrenia.
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Affiliation(s)
- Jing Zhang
- College of Biomedical Engineering, Sichuan University, Chengdu, China
| | - Hui Yang
- College of Biomedical Engineering, Sichuan University, Chengdu, China
| | - Wen Li
- College of Biomedical Engineering, Sichuan University, Chengdu, China
| | - Yuanyuan Li
- Mental Health Center, West China Hospital of Sichuan University, Chengdu, China
| | - Jing Qin
- Centre for Smart Health, School of Nursing, The Hong Kong Polytechnic University, Hong Kong, Hong Kong SAR, China
| | - Ling He
- College of Biomedical Engineering, Sichuan University, Chengdu, China
- *Correspondence: Ling He
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7
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Manning C, Hulks V, Tibber MS, Dakin SC. Integration of visual motion and orientation signals in dyslexic children: an equivalent noise approach. ROYAL SOCIETY OPEN SCIENCE 2022; 9:200414. [PMID: 35592763 PMCID: PMC9066306 DOI: 10.1098/rsos.200414] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 04/01/2022] [Indexed: 06/15/2023]
Abstract
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.
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Affiliation(s)
- Catherine Manning
- Department of Experimental Psychology, University of Oxford, UK
- School of Psychology and Clinical Language Sciences, University of Reading, UK
| | - Victoria Hulks
- Department of Experimental Psychology, University of Oxford, UK
| | - Marc S. Tibber
- Department of Clinical, Educational and Health Psychology, UCL, UK
| | - Steven C. Dakin
- School of Optometry and Vision Science, University of Auckland, New Zealand
- UCL Institute of Ophthalmology, University College London, UK
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8
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Is there magnocellular facilitation of early neural processes underlying visual word recognition? Evidence from masked repetition priming with ERPs. Neuropsychologia 2022; 170:108230. [PMID: 35395249 DOI: 10.1016/j.neuropsychologia.2022.108230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 03/14/2022] [Accepted: 03/29/2022] [Indexed: 11/22/2022]
Abstract
An influential theory in the field of visual object recognition proposes that it is the fast magnocellular (M) system that facilitates neural processing of spatially more fine-grained information rather the slower parvocellular (P) system. While written words can be considered as a special type of visual objects, it is unknown whether magnocellular facilitation also plays a role in reading. We used a masked priming paradigm that has been shown to result in neural facilitation in visual word processing and tested whether these facilitating effects are mediated by the magnocellular system. In two experiments, we manipulated the influence of magnocellular and parvocellular systems on visual processing of a contextually predictable target character by contrasting high versus low spatial frequency and luminance versus color contrast, respectively. In addition, unchanged (normal) primes were included in both experiments as a manipulation check. As expected, unchanged primes elicited typical repetition effects in the N1, N250 and P3 components of the ERP in both experiments. In the experiment manipulating spatial contrast, we obtained repetition effects only for the N1 component for both M- and P-biased primes. In the luminance versus color contrast experiment, repetition effects were found in N1 and N250 for both M- and P- biased primes. Furthermore, no interactions were found between M-vs. P-biased prime types and repetition. Together these results indicate that M- and P- information contributes jointly to early neural processes underlying visual word recognition.
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9
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Perani D, Scifo P, Cicchini GM, Rosa PD, Banfi C, Mascheretti S, Falini A, Marino C, Morrone MC. White matter deficits correlate with visual motion perception impairments in dyslexic carriers of the DCDC2 genetic risk variant. Exp Brain Res 2021; 239:2725-2740. [PMID: 34228165 PMCID: PMC8448712 DOI: 10.1007/s00221-021-06137-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 05/12/2021] [Indexed: 02/07/2023]
Abstract
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.
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Affiliation(s)
- Daniela Perani
- Vita-Salute San Raffaele University, Milan, Italy.,C.E.R.M.A.C. (Centro di Risonanza Magnetica ad Alto Campo), Milan, Italy.,Nuclear Medicine Department, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Paola Scifo
- C.E.R.M.A.C. (Centro di Risonanza Magnetica ad Alto Campo), Milan, Italy.,Nuclear Medicine Department, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Guido M Cicchini
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy.
| | - Pasquale Della Rosa
- C.E.R.M.A.C. (Centro di Risonanza Magnetica ad Alto Campo), Milan, Italy.,Unit of Neuroradiology, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Chiara Banfi
- Institute of Psychology, University of Graz, Graz, Austria
| | - Sara Mascheretti
- Child Psychopathology Unit, Scientific Institute Eugenio Medea, Bosisio Parini, Italy
| | - Andrea Falini
- Vita-Salute San Raffaele University, Milan, Italy.,C.E.R.M.A.C. (Centro di Risonanza Magnetica ad Alto Campo), Milan, Italy.,Unit of Neuroradiology, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Cecilia Marino
- Department of Psychiatry, Unviersity of Toronto, Toronto, Canada.,Division of Child and Youth Psychiatry, Centre for Addiction and Mental Health (CAMH), Toronto, Canada
| | - Maria Concetta Morrone
- Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.,Scientific Institute Stella Maris (IRCSS), Pisa, Italy
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10
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Abstract
The scientific study of reading has a rich history that spans disciplines from vision science to linguistics, psychology, cognitive neuroscience, neurology, and education. The study of reading can elucidate important general mechanisms in spatial vision, attentional control, object recognition, and perceptual learning, as well as the principles of plasticity and cortical topography. However, literacy also prompts the development of specific neural circuits to process a unique and artificial stimulus. In this review, we describe the sequence of operations that transforms visual features into language, how the key neural circuits are sculpted by experience during development, and what goes awry in children for whom learning to read is a struggle. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Jason D Yeatman
- Graduate School of Education, Stanford University, Stanford, California 93405, USA; .,Division of Developmental-Behavioral Pediatrics, Stanford University School of Medicine, Stanford, California 94305, USA.,Department of Psychology, Stanford University, Stanford, California 94305, USA
| | - Alex L White
- Graduate School of Education, Stanford University, Stanford, California 93405, USA; .,Division of Developmental-Behavioral Pediatrics, Stanford University School of Medicine, Stanford, California 94305, USA.,Department of Neuroscience and Behavior, Barnard College, New York, New York 10027, USA
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Mascheretti S, Peruzzo D, Andreola C, Villa M, Ciceri T, Trezzi V, Marino C, Arrigoni F. Selecting the Most Relevant Brain Regions to Classify Children with Developmental Dyslexia and Typical Readers by Using Complex Magnocellular Stimuli and Multiple Kernel Learning. Brain Sci 2021; 11:brainsci11060722. [PMID: 34071649 PMCID: PMC8228080 DOI: 10.3390/brainsci11060722] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 05/20/2021] [Accepted: 05/25/2021] [Indexed: 11/16/2022] Open
Abstract
Increasing evidence supports the presence of deficits in the visual magnocellular (M) system in developmental dyslexia (DD). The M system is related to the fronto-parietal attentional network. Previous neuroimaging studies have revealed reduced/absent activation within the visual M pathway in DD, but they have failed to characterize the extensive brain network activated by M stimuli. We performed a multivariate pattern analysis on a Region of Interest (ROI) level to differentiate between children with DD and age-matched typical readers (TRs) by combining full-field sinusoidal gratings, controlled for spatial and temporal frequencies and luminance contrast, and a coherent motion (CM) sensitivity task at 6%-CML6, 15%-CML15 and 40%-CML40. ROIs spanning the entire visual dorsal stream and ventral attention network (VAN) had higher discriminative weights and showed higher act1ivation in TRs than in children with DD. Of the two tasks, CM had the greatest weight when classifying TRs and children with DD in most of the ROIs spanning these streams. For the CML6, activation within the right superior parietal cortex positively correlated with reading skills. Our approach highlighted the dorsal stream and the VAN as highly discriminative areas between children with DD and TRs and allowed for a better characterization of the "dorsal stream vulnerability" underlying DD.
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Affiliation(s)
- Sara Mascheretti
- Child Psychopathology Unit, Scientific Institute, IRCCS Eugenio Medea, 23842 Bosisio Parini, Italy; (C.A.); (M.V.); (V.T.)
- Correspondence: (S.M.); (F.A.)
| | - Denis Peruzzo
- Neuroimaging Lab, Scientific Institute, IRCCS Eugenio Medea, 23842 Bosisio Parini, Italy; (D.P.); (T.C.)
| | - Chiara Andreola
- Child Psychopathology Unit, Scientific Institute, IRCCS Eugenio Medea, 23842 Bosisio Parini, Italy; (C.A.); (M.V.); (V.T.)
- Laboratoire de Psychologie de Développement et de l’Éducation de l’Enfant (LaPsyDÉ), Université de Paris, 75005 Paris, France
| | - Martina Villa
- Child Psychopathology Unit, Scientific Institute, IRCCS Eugenio Medea, 23842 Bosisio Parini, Italy; (C.A.); (M.V.); (V.T.)
| | - Tommaso Ciceri
- Neuroimaging Lab, Scientific Institute, IRCCS Eugenio Medea, 23842 Bosisio Parini, Italy; (D.P.); (T.C.)
| | - Vittoria Trezzi
- Child Psychopathology Unit, Scientific Institute, IRCCS Eugenio Medea, 23842 Bosisio Parini, Italy; (C.A.); (M.V.); (V.T.)
| | - Cecilia Marino
- The Division of Child and Youth Psychiatry at the Centre for Addiction and Mental Health (CAMH), Toronto, ON M6J 1H4, Canada;
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
| | - Filippo Arrigoni
- Neuroimaging Lab, Scientific Institute, IRCCS Eugenio Medea, 23842 Bosisio Parini, Italy; (D.P.); (T.C.)
- Correspondence: (S.M.); (F.A.)
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12
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Abstract
A universal signature of developmental dyslexia is literacy acquisition impairments. Besides, dyslexia may be related to deficits in selective spatial attention, in the sensitivity to global visual motion, speed processing, oculomotor coordination, and integration of auditory and visual information. Whether motion-sensitive brain areas of children with dyslexia can recognize different speeds of expanded optic flow and segregate the slow-speed from high-speed contrast of motion was a main question of the study. A combined event-related EEG experiment with optic flow visual stimulation and functional frequency-based graph approach (small-world propensity ϕ) were applied to research the responsiveness of areas, which are sensitive to motion, and also distinguish slow/fast -motion conditions on three groups of children: controls, untrained (pre-D) and trained dyslexics (post-D) with visual intervention programs. Lower ϕ at θ, α, γ1-frequencies (low-speed contrast) for controls than other groups represent that the networks rewire, expressed at β frequencies (both speed contrasts) in the post-D, whose network was most segregated. Functional connectivity nodes have not existed in pre-D at dorsal medial temporal area MT+/V5 (middle, superior temporal gyri), left-hemispheric middle occipital gyrus/visual V2, ventral occipitotemporal (fusiform gyrus/visual V4), ventral intraparietal (supramarginal, angular gyri), derived from θ-frequency network for both conditions. After visual training, compensatory mechanisms appeared to implicate/regain these brain areas in the left hemisphere through plasticity across extended brain networks. Specifically, for high-speed contrast, the nodes were observed in pre-D (θ-frequency) and post-D (β2-frequency) relative to controls in hyperactivity of the right dorsolateral prefrontal cortex, which might account for the attentional network and oculomotor control impairments in developmental dyslexia.
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Beyond Reading Modulation: Temporo-Parietal tDCS Alters Visuo-Spatial Attention and Motion Perception in Dyslexia. Brain Sci 2021; 11:brainsci11020263. [PMID: 33669651 PMCID: PMC7922381 DOI: 10.3390/brainsci11020263] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 02/13/2021] [Accepted: 02/16/2021] [Indexed: 01/17/2023] Open
Abstract
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.
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14
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Abstract
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.
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15
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Benson PJ, Wallace L, Beedie SA. Sensory auditory interval perception errors in developmental dyslexia. Neuropsychologia 2020; 147:107587. [DOI: 10.1016/j.neuropsychologia.2020.107587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 08/15/2020] [Accepted: 08/17/2020] [Indexed: 11/16/2022]
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16
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Schiavi C, Finzi A, Cellini M. Steady-State Pattern Electroretinogram and Frequency Doubling Technology in Adult Dyslexic Readers. Clin Ophthalmol 2019; 13:2451-2459. [PMID: 31849443 PMCID: PMC6912011 DOI: 10.2147/opth.s229898] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Accepted: 11/27/2019] [Indexed: 11/23/2022] Open
Abstract
Purpose Dyslexia is a reading disorder with neurological deficit of the magnocellular pathway. The aim of our study was to evaluate the functionality of the magnocellular-Y (M-Y) retinal ganglion cells in adult dyslexic subjects using steady-state pattern electroretinogram and frequency doubling perimetry. Methods Ten patients with dyslexia (7 females and 3 males), mean age 28.7 ± 5.9 years, and 10 subjects without dyslexia (6 females and 4 males), mean age 27.8 ± 4.1 years, were enrolled in the study and underwent both steady-state pattern-electroretinogram examination and frequency doubling perimetry. Results There was a significant difference in the amplitude of the steady-state pattern electroretinogram of the dyslexic group and the healthy controls (0.610±0.110 μV vs 1.250±0.296 μV; p=0.0001). Furthermore, in the dyslexic group we found a significant difference between the right eye and the left eye (0.671±0.11 μV vs 0.559±0.15 μV; p=0.001). With frequency doubling perimetry, the pattern standard deviation index increased in dyslexic eyes compared to healthy controls (4.40±0.81 dB vs 2.99±0.35 dB; p=0.0001) and in the left eye versus the right eye of the dyslexic group (4.43±1.10 dB vs 3.66±0.96 dB; p=0.031). There was a correlation between the reduction in the wave amplitude of the pattern electroretinogram and the simultaneous increase in the pattern standard deviation values (r=0.80; p=0.001). This correlation was also found to be present in the left eye (r=0.93; p<0.001) and the right eye (r=0.81; p=0.005) of dyslexic subjects. Conclusion Our study shows that there was an alteration of the activity of M-Y retinal ganglion cells, especially in the left eye. It confirms that in dyslexia there is a deficit of visual attention with damage not only of the magnocellular-dorsal pathway but also of the M-Y retinal ganglion cells.
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Affiliation(s)
- Costantino Schiavi
- Department of Experimental, Diagnostic, and Specialty Medicine, Ophthalmology Service, University of Bologna, Bologna 40138, Italy
| | - Alessandro Finzi
- Department of Experimental, Diagnostic, and Specialty Medicine, Ophthalmology Service, University of Bologna, Bologna 40138, Italy
| | - Mauro Cellini
- Department of Experimental, Diagnostic, and Specialty Medicine, Ophthalmology Service, University of Bologna, Bologna 40138, Italy
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17
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White AL, Boynton GM, Yeatman JD. The link between reading ability and visual spatial attention across development. Cortex 2019; 121:44-59. [PMID: 31542467 DOI: 10.1016/j.cortex.2019.08.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 07/11/2019] [Accepted: 08/16/2019] [Indexed: 10/26/2022]
Abstract
Interacting with a cluttered and dynamic environment requires making decisions about visual information at relevant locations while ignoring irrelevant locations. Typical adults can do this with covert spatial attention: prioritizing particular visual field locations even without moving the eyes. Deficits of covert spatial attention have been implicated in developmental dyslexia, a specific reading disability. Previous studies of children with dyslexia, however, have been complicated by group differences in overall task ability that are difficult to distinguish from selective spatial attention. Here, we used a single-fixation visual search task to estimate orientation discrimination thresholds with and without an informative spatial cue in a large sample (N = 123) of people ranging in age from 5 to 70 years and with a wide range of reading abilities. We assessed the efficiency of attentional selection via the cueing effect: the difference in log thresholds with and without the spatial cue. Across our whole sample, both absolute thresholds and the cueing effect gradually improved throughout childhood and adolescence. Compared to typical readers, individuals with dyslexia had higher thresholds (worse orientation discrimination) as well as smaller cueing effects (weaker attentional selection). Those differences in dyslexia were especially pronounced prior to age 20, when basic visual function is still maturing. Thus, in line with previous theories, literacy skills are associated with the development of selective spatial attention.
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Affiliation(s)
- Alex L White
- Institute for Learning & Brain Sciences, University of Washington, Seattle, United States; Department of Speech & Hearing Sciences, University of Washington, Seattle, United States.
| | - Geoffrey M Boynton
- Department of Psychology, University of Washington, Seattle, United States
| | - Jason D Yeatman
- Institute for Learning & Brain Sciences, University of Washington, Seattle, United States; Department of Speech & Hearing Sciences, University of Washington, Seattle, United States
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18
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Manning C, Kaneshiro B, Kohler PJ, Duta M, Scerif G, Norcia AM. Neural dynamics underlying coherent motion perception in children and adults. Dev Cogn Neurosci 2019; 38:100670. [PMID: 31228678 PMCID: PMC6688051 DOI: 10.1016/j.dcn.2019.100670] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 05/20/2019] [Accepted: 06/10/2019] [Indexed: 01/30/2023] Open
Abstract
Motion sensitivity increases during childhood, but little is known about the neural correlates. Most studies investigating children's evoked responses have not dissociated direction-specific and non-direction-specific responses. To isolate direction-specific responses, we presented coherently moving dot stimuli preceded by incoherent motion, to 6- to 7-year-olds (n = 34), 8- to 10-year-olds (n = 34), 10- to 12-year-olds (n = 34) and adults (n = 20). Participants reported the coherent motion direction while high-density EEG was recorded. Using a data-driven approach, we identified two stimulus-locked EEG components with distinct topographies: an early component with an occipital topography likely reflecting sensory encoding and a later, sustained positive component over centro-parietal electrodes that we attribute to decision-related processes. The component waveforms showed clear age-related differences. In the early, occipital component, all groups showed a negativity peaking at ˜300 ms, like the previously reported coherent-motion N2. However, the children, unlike adults, showed an additional positive peak at ˜200 ms, suggesting differential stimulus encoding. The later positivity in the centro-parietal component rose more steeply for adults than for the youngest children, likely reflecting age-related speeding of decision-making. We conclude that children's protracted development of coherent motion sensitivity is associated with maturation of both early sensory and later decision-related processes.
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Affiliation(s)
- Catherine Manning
- Department of Experimental Psychology, University of Oxford, Anna Watts Building, Radcliffe Observatory Quarter, Woodstock Road, Oxford, OX2 6GG, UK.
| | - Blair Kaneshiro
- Department of Otolaryngology Head and Neck Surgery, Stanford University School of Medicine, Stanford University, 2452 Watson Court, Palo Alto, CA, 94303, USA
| | - Peter J Kohler
- Department of Psychology, Stanford University, Jordan Hall, 450 Serra Mall, Stanford, CA, 94305, USA
| | - Mihaela Duta
- Department of Experimental Psychology, University of Oxford, Anna Watts Building, Radcliffe Observatory Quarter, Woodstock Road, Oxford, OX2 6GG, UK
| | - Gaia Scerif
- Department of Experimental Psychology, University of Oxford, Anna Watts Building, Radcliffe Observatory Quarter, Woodstock Road, Oxford, OX2 6GG, UK
| | - Anthony M Norcia
- Department of Psychology, Stanford University, Jordan Hall, 450 Serra Mall, Stanford, CA, 94305, USA
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19
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The current status of the magnocellular theory of developmental dyslexia. Neuropsychologia 2019; 130:66-77. [DOI: 10.1016/j.neuropsychologia.2018.03.022] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 12/15/2017] [Accepted: 03/19/2018] [Indexed: 01/28/2023]
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20
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Contemori G, Battaglini L, Barollo M, Ciavarelli A, Casco C. Developmental dyslexia: A deficit in magnocellular-parvocellular co-activation, not simply in pure magnocellular activation. Vision Res 2019; 159:61-67. [DOI: 10.1016/j.visres.2019.03.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 03/08/2019] [Accepted: 03/20/2019] [Indexed: 01/25/2023]
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21
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D'Mello AM, Gabrieli JDE. Cognitive Neuroscience of Dyslexia. Lang Speech Hear Serv Sch 2019; 49:798-809. [PMID: 30458541 DOI: 10.1044/2018_lshss-dyslc-18-0020] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 05/08/2018] [Indexed: 01/16/2023] Open
Abstract
Purpose This review summarizes what is known about the structural and functional brain bases of dyslexia. Method We review the current literature on structural and functional brain differences in dyslexia. This includes evidence about differences in gray matter anatomy, white matter connectivity, and functional activations in response to print and language. We also summarize findings concerning brain plasticity in response to interventions. Results We highlight evidence relating brain function and structure to instructional issues such as diagnosis and prognosis. We also highlight evidence about brain differences in early childhood, before formal reading instruction in school, which supports the importance of early identification and intervention. Conclusion Neuroimaging studies of dyslexia reveal how the disorder is related to differences in structure and function in multiple neural circuits.
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Affiliation(s)
- Anila M D'Mello
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge.,McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge
| | - John D E Gabrieli
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge.,McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge
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22
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Flint S, Pammer K. It is the egg, not the chicken; dorsal visual deficits present in dyslexia are not present in illiterate adults. DYSLEXIA (CHICHESTER, ENGLAND) 2019; 25:69-83. [PMID: 30592104 DOI: 10.1002/dys.1607] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 09/03/2018] [Accepted: 12/05/2018] [Indexed: 06/09/2023]
Abstract
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.
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Affiliation(s)
- Sarah Flint
- The Research School of Psychology, The Australian National University, Canberra, Australia
| | - Kristen Pammer
- The School of Psychology, The University of Newcastle, Newcastle, Australia
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23
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Whitford V, O'Driscoll GA, Titone D. Reading deficits in schizophrenia and their relationship to developmental dyslexia: A review. Schizophr Res 2018; 193:11-22. [PMID: 28688740 DOI: 10.1016/j.schres.2017.06.049] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 06/23/2017] [Accepted: 06/23/2017] [Indexed: 12/12/2022]
Abstract
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.
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Affiliation(s)
- Veronica Whitford
- Department of Brain and Cognitive Sciences, McGovern Institute for Brain Research, Massachusetts Institute of Technology, 43 Vassar Street, Cambridge, MA 02139, United States; Graduate School of Education, Harvard University, 13 Appian Way, Cambridge, MA 02138, United States.
| | - Gillian A O'Driscoll
- Department of Psychology, McGill University, 1205 Doctor Penfield Avenue, Montreal, QC H3A 1B1, Canada; Department of Psychiatry, McGill University, 1033 Pine Avenue West, Montreal, QC H3A 1A1, Canada; Douglas Mental Health University Institute, McGill University, 6875 LaSalle Boulevard, Verdun, QC H4H 1R3, Canada; Montreal Neurological Institute and Hospital, McGill University, 3801 University Street, Montreal, QC H3A 2B4, Canada.
| | - Debra Titone
- Department of Psychology, McGill University, 1205 Doctor Penfield Avenue, Montreal, QC H3A 1B1, Canada; Centre for Research on Brain, Language and Music, McGill University, 3640 de la Montagne Street, Montreal, QC H3G 2A8, Canada.
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24
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Rendall AR, Perrino PA, LoTurco JJ, Fitch RH. Evaluation of visual motion perception ability in mice with knockout of the dyslexia candidate susceptibility gene Dcdc2. GENES BRAIN AND BEHAVIOR 2018; 18:e12450. [PMID: 29232042 DOI: 10.1111/gbb.12450] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 12/08/2017] [Accepted: 12/08/2017] [Indexed: 12/17/2022]
Abstract
Developmental dyslexia is a heritable disability characterized by difficulties in learning to read and write. The neurobiological and genetic mechanisms underlying dyslexia remain poorly understood; however, several dyslexia candidate risk genes have been identified. One of these candidate risk genes-doublecortin domain containing 2 (DCDC2)-has been shown to play a role in neuronal migration and cilia function. At a behavioral level, variants of DCDC2 have been associated with impairments in phonological processing, working memory and reading speed. Additionally, a specific mutation in DCDC2 has been strongly linked to deficits in motion perception-a skill subserving reading abilities. To further explore the relationship between DCDC2 and dyslexia, a genetic knockout (KO) of the rodent homolog of DCDC2 (Dcdc2) was created. Initial studies showed that Dcdc2 KOs display deficits in auditory processing and working memory. The current study was designed to evaluate the association between DCDC2 and motion perception, as these skills have not yet been assessed in the Dcdc2 KO mouse model. We developed a novel motion perception task, utilizing touchscreen technology and operant conditioning. Dcdc2 KOs displayed deficits on the Pairwise Discrimination task specifically as motion was added to visual stimuli. Following behavioral assessment, brains were histologically prepared for neuroanatomical analysis of the lateral geniculate nucleus (LGN). The cumulative distribution showed that Dcdc2 KOs exhibited more small neurons and fewer larger neurons in the LGN. Results compliment findings that DCDC2 genetic alteration results in anomalies in visual motion pathways in a subpopulation of dyslexic patients.
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Affiliation(s)
- A R Rendall
- Department of Psychology/Behavioral Neuroscience and Institute for Systems Genomics, University of Connecticut, Storrs, Connecticut
| | - P A Perrino
- Department of Psychology/Behavioral Neuroscience and Institute for Systems Genomics, University of Connecticut, Storrs, Connecticut
| | - J J LoTurco
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - R H Fitch
- Department of Psychology/Behavioral Neuroscience and Institute for Systems Genomics, University of Connecticut, Storrs, Connecticut
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25
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Shandiz JH, Heyrani M, Sobhani-Rad D, Salehinejad Z, Shojaei S, Khoshsima MJ, Azimi A, Yekta AA, Yazdi SHH. Pattern Visual Evoked Potentials in Dyslexic Children. J Ophthalmic Vis Res 2017; 12:402-406. [PMID: 29090050 PMCID: PMC5644407 DOI: 10.4103/jovr.jovr_106_16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
PURPOSE This study aimed to compare pattern visual evoked potential (PVEP) components in dyslexic and normal children. METHODS This cross-sectional analytic study recruited 72 children, including 36 dyslexic and 36 normal participants aged 8-12 years. Visual examinations included measurement of distance visual acuity, refraction, and PVEP components of amplitudes and latencies with two different check sizes of 15 and 60 minutes (min) of arc at two contrast levels of 25% and 100%. RESULTS Our results demonstrated significant differences between dyslexic and normal children in terms of P100 latency and amplitude of PVEP at 25% contrast, with check sizes of 15 and 60 min of arc. However, there were no significant differences between the two groups regarding P100 latency and amplitude at 100% contrast with check sizes of both 15 and 60 min of arc. CONCLUSION Dyslexic participants showed reduced amplitude and prolonged latency in most PVEP components at low-contrast levels. These findings may support the magnocellular deficit hypothesis in dyslexic participants, even though the parvocellular pathway remains intact.
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Affiliation(s)
- Javad Heravian Shandiz
- Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.,Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mohsen Heyrani
- Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.,Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Davood Sobhani-Rad
- Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.,Department of Speech Therapy, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Zeinab Salehinejad
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Shirin Shojaei
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mohamad Javad Khoshsima
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Abbas Azimi
- Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.,Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Abbas Ali Yekta
- Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.,Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Seyed Hosein Hoseini Yazdi
- Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, Australia
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26
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Bowns L, Beaudot WHA. Measuring Early Cortical Visual Processing in the Clinic. Iperception 2017; 8:2041669517702915. [PMID: 28567268 PMCID: PMC5438040 DOI: 10.1177/2041669517702915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We describe a mobile app that measures early cortical visual processing suitable for use in clinics. The app is called Component Extraction and Motion Integration Test (CEMIT). Observers are asked to respond to the direction of translating plaids that move in one of two very different directions. The plaids have been selected so that the plaid components move in one of the directions and the plaid pattern moves in the other direction. In addition to correctly responding to the pattern motion, observers demonstrate their ability to correctly extract the movement (and therefore the orientation) of the underlying components at specific spatial frequencies. We wanted to test CEMIT by seeing if we could replicate the broader tuning observed at low spatial frequencies for this type of plaid. Results from CEMIT were robust and successfully replicated this result for 50 typical observers. We envisage that it will be of use to researchers and clinicians by allowing them to investigate specific deficits at this fundamental level of cortical visual processing. CEMIT may also be used for screening purposes where visual information plays an important role, for example, air traffic controllers.
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27
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van de Ven V, Rotarska Jagiela A, Oertel-Knöchel V, Linden DEJ. Reduced intrinsic visual cortical connectivity is associated with impaired perceptual closure in schizophrenia. NEUROIMAGE-CLINICAL 2017; 15:45-52. [PMID: 28480163 PMCID: PMC5407639 DOI: 10.1016/j.nicl.2017.04.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Revised: 04/14/2017] [Accepted: 04/15/2017] [Indexed: 11/24/2022]
Abstract
Sensory perceptual processing deficits, such as impaired visual object identification and perceptual closure, have been reported in schizophrenia. These perceptual impairments may be associated with neural deficits in visual association areas, including lateral occipital cortex and inferior temporal areas. However, it remains unknown if such deficits can be found in the intrinsic architecture of the visual system. In the current study, we measured perceptual closure performance and resting-state functional connectivity using functional magnetic resonance imaging (FMRI) in 16 schizophrenia patients and 16 matched healthy controls. We estimated intrinsic functional connectivity using self-organized grouping spatial ICA, which clusters component maps in the subject space according to spatial similarity. Patients performed worse than controls in the perceptual closure task. This impaired closure performance of patients was correlated with increased severity of psychotic symptoms. We also found that intrinsic connectivity of the visual processing system was diminished in patients compared to controls. Lower perceptual closure performance was correlated to lower visual cortical intrinsic connectivity overall. We suggest that schizophrenia is associated with impaired intrinsic connectivity of the visual system, and that it is a potential mechanism leading to impaired visual object perception. These findings contribute to increasing evidence for impairments of higher visual functions in schizophrenia. We found reduced visual resting-state network connectivity in schizophrenia. Reduced connectivity correlated with impaired perceptual closure performance Schizophrenia is associated with impaired intrinsic connectivity of the visual system.
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Affiliation(s)
- Vincent van de Ven
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, The Netherlands.
| | - Anna Rotarska Jagiela
- Laboratory of Neuroimaging, Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe University, Frankfurt/Main 60528, Germany
| | - Viola Oertel-Knöchel
- Laboratory of Neuroimaging, Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe University, Frankfurt/Main 60528, Germany
| | - David E J Linden
- MRC Centre for Neuropsychiatric Genetics & Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, United Kingdom
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28
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Chen L, Zhang M, Ai F, Xie W, Meng X. Crossmodal synesthetic congruency improves visual timing in dyslexic children. RESEARCH IN DEVELOPMENTAL DISABILITIES 2016; 55:14-26. [PMID: 27022720 DOI: 10.1016/j.ridd.2016.03.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2015] [Revised: 03/11/2016] [Accepted: 03/17/2016] [Indexed: 06/05/2023]
Abstract
Consistent with the temporal ventriloquism effect, synesthetic correspondence between the features of visual size and auditory pitch has been shown to modulate the performance of visual temporal order judgment (TOJ) in typical adults. Here in the two main experiments we recruited seventeen dyslexic children and twenty typically developing children to perform a visual TOJ task and measured their ability of synesthetic correspondence between visual size and auditory pitch. In Experiment 1, participants were shown two consecutively presented visual discs that were temporally flanked by two synesthetic congruent or incongruent auditory beeps. In Experiment 2, participants received a crossmodal matching test (visual-size vs. auditory pitch). The results showed that compared to the typically developing group, dyslexic children benefited more from cross-modal synesthetic correspondence to partially compensate for their deficiency in visual TOJ task. The multisensory facilitation for timing performance was correlated with reading ability (Exp.1). Moreover, dyslexic children formed intact "congruent" matching of visually larger shapes to lower auditory pitch, and visually smaller shapes to higher auditory pitch, as did their typically developing peers (Exp 2). The results of our present study suggested general deficits of temporal processing in dyslexic children, However, with relatively intact ability of auditory pitch-visual size matching, dyslexic children could separate visual events using auditory cues. The current study also indicates a feasible way to improve the reading ability by exploiting temporal ventriloquism effect, modulated by appropriate crossmodal synesthetic associations.
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Affiliation(s)
- Lihan Chen
- Department of Psychology and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100871, China; Key Laboratory of Machine Perception (Ministry of Education), Peking University, Beijing 100871, China.
| | - Manli Zhang
- Department of Psychology and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100871, China
| | - Feng Ai
- Department of Psychology and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100871, China
| | - Weiyi Xie
- Department of Psychology and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100871, China
| | - Xiangzhi Meng
- Department of Psychology and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100871, China
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The Interpretation of Emotion from Facial Expression for Children with Visual Processing Problems. ACTA ACUST UNITED AC 2016. [DOI: 10.1017/s1030011200025045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A significant proportion of people with learning difficulties have social problems, which are often considered to be the product of school failure. However, a number of studies have suggested that these social skill problems may relate to the inability to decode subtle visual cues of body language and facial expression. The majority of studies of facial expression, however, have viewed learning disability as a unitary condition, without taking account of specific sub‐types which may have more difficulty in processing visual cues, especially for facial emotion. This study investigated children aged 8 to 12 years who were divided into three learning disability sub‐groups: 1) a visual‐perceptual sub‐type called Irlen Syndrome (n=41); 2) a group with learning disabilities, but no indications of Irlen Syndrome (n=30); and 3) a normally achieving control group (n=31). The Irlen Syndrome sub‐group had significantly lower scores for interpreting emotion from facial expression than the two other groups. The learning disabled non‐lrlen sub‐group also had significantly lower scores than the control group, but with much smaller levels of significance than those between the Irlen and control groups.
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Abstract
Dyslexia is a specific impairment in reading that affects 1 in 10 people. Previous studies have failed to isolate a single cause of the disorder, but several candidate genes have been reported. We measured motion perception in two groups of dyslexics, with and without a deletion within the DCDC2 gene, a risk gene for dyslexia. We found impairment for motion particularly strong at high spatial frequencies in the population carrying the deletion. The data suggest that deficits in motion processing occur in a specific genotype, rather than the entire dyslexia population, contributing to the large variability in impairment of motion thresholds in dyslexia reported in the literature.
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Kassaliete E, Lacis I, Fomins S, Krumina G. Reading and coherent motion perception in school age children. ANNALS OF DYSLEXIA 2015; 65:69-83. [PMID: 25911276 DOI: 10.1007/s11881-015-0099-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 03/04/2015] [Indexed: 06/04/2023]
Abstract
This study includes an evaluation, according to age, of the reading and global motion perception developmental trajectories of 2027 school age children in typical stages of development. Reading is assessed using the reading rate score test, for which all of the student participants, regardless of age, received the same passage of text of a medium difficulty reading level. The coherent motion perception threshold is determined according to the adaptive psychophysical protocol based on a four-alternative, forced-choice procedure. Three different dot velocities: 2, 5, and 8 deg/s were used for both assemblies of coherent or randomly moving dots. Reading rate score test results exhibit a wide dispersion across all age groups, so much so that the outlier data overlap, for both the 8 and 18-year-old student-participant age groups. Latvian children's reading fluency developmental trajectories reach maturation at 12-13 years of age. After the age of 13, reading rate scores increase slowly; however, the linear regression slope is different from zero and positive: F(1, 827) = 45.3; p < 0.0001. One hundred eighty-one student-participants having results below the 10th percentile were classified as weak readers in our study group. The reading fluency developmental trajectory of this particular group of student-participants does not exhibit any statistically significant saturation until the age of 18 years old. Coherent motion detection thresholds decrease with age and do not reach saturation. Tests with slower moving dots (2 deg/s) yield results that exhibit significant differences between strong and weak readers.
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Affiliation(s)
- Evita Kassaliete
- Department of Optometry and Vision Science, University of Latvia, 8Kengaraga Str., Riga, LV - 1063, Latvia,
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Qian Y, Deng Y, Zhao J, Bi HY. Magnocellular-dorsal pathway function is associated with orthographic but not phonological skill: fMRI evidence from skilled Chinese readers. Neuropsychologia 2015; 71:84-90. [PMID: 25813780 DOI: 10.1016/j.neuropsychologia.2015.03.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 03/18/2015] [Accepted: 03/22/2015] [Indexed: 10/23/2022]
Abstract
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.
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Affiliation(s)
- Yi Qian
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, 16 Lincui Road, Chaoyang District, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuan Deng
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, 16 Lincui Road, Chaoyang District, Beijing 100101, China.
| | - Jing Zhao
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, 16 Lincui Road, Chaoyang District, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hong-Yan Bi
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, 16 Lincui Road, Chaoyang District, Beijing 100101, China.
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Giraldo-Chica M, Hegarty JP, Schneider KA. Morphological differences in the lateral geniculate nucleus associated with dyslexia. NEUROIMAGE-CLINICAL 2015; 7:830-6. [PMID: 26082892 PMCID: PMC4459050 DOI: 10.1016/j.nicl.2015.03.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 03/06/2015] [Accepted: 03/13/2015] [Indexed: 11/16/2022]
Abstract
Developmental dyslexia is a common learning disability characterized by normal intelligence but difficulty in skills associated with reading, writing and spelling. One of the most prominent, albeit controversial, theories of dyslexia is the magnocellular theory, which suggests that malfunction of the magnocellular system in the brain is responsible for the behavioral deficits. We sought to test the basis of this theory by directly measuring the lateral geniculate nucleus (LGN), the only location in the brain where the magnocellular and parvocellular streams are spatially disjoint. Using high-resolution proton-density weighted MRI scans, we precisely measured the anatomical boundaries of the LGN in 13 subjects with dyslexia (five female) and 13 controls (three female), all 22–26 years old. The left LGN was significantly smaller in volume in subjects with dyslexia and also differed in shape; no differences were observed in the right LGN. The functional significance of this asymmetry is unknown, but these results are consistent with the magnocellular theory and support theories of dyslexia that involve differences in the early visual system. The first direct test of the magnocellular hypothesis of dyslexia in vivo The first measurements of the LGN in living subjects with dyslexia The LGN are smaller in subjects with dyslexia and differ morphologically
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Affiliation(s)
- Mónica Giraldo-Chica
- Centre for Vision Research, York University, Toronto, Ontario M3J 1P3, Canada ; Department of Medicine, University of Barcelona, Barcelona, Catalonia, Spain
| | - John P Hegarty
- Department of Psychological Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Keith A Schneider
- Centre for Vision Research, York University, Toronto, Ontario M3J 1P3, Canada ; Department of Psychological Sciences, University of Missouri, Columbia, MO 65211, USA ; Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada
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Skottun BC. The need to differentiate the magnocellular system from the dorsal stream in connection with dyslexia. Brain Cogn 2015; 95:62-6. [PMID: 25699484 DOI: 10.1016/j.bandc.2015.01.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 01/06/2015] [Accepted: 01/07/2015] [Indexed: 01/09/2023]
Abstract
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.
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35
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Main KL, Pestilli F, Mezer A, Yeatman J, Martin R, Phipps S, Wandell B. Speed discrimination predicts word but not pseudo-word reading rate in adults and children. BRAIN AND LANGUAGE 2014; 138:27-37. [PMID: 25278418 PMCID: PMC4300234 DOI: 10.1016/j.bandl.2014.09.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 04/30/2014] [Accepted: 09/02/2014] [Indexed: 06/03/2023]
Abstract
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.
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Affiliation(s)
- Keith L Main
- Department of Psychology, Stanford University, Stanford, CA, United States; War Related Illness and Injury Study Center, Veterans Affairs, Palo Alto Health Care System (VAPAHCS), Palo Alto, CA, United States; Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, United States
| | - Franco Pestilli
- Department of Psychology, Stanford University, Stanford, CA, United States.
| | - Aviv Mezer
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Jason Yeatman
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Ryan Martin
- Department of Psychology, Loyola Marymount University, Los Angeles, CA, United States
| | - Stephanie Phipps
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Brian Wandell
- Department of Psychology, Stanford University, Stanford, CA, United States
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Abstract
Dyslexia is more than just difficulty with translating letters into sounds. Many dyslexics have problems with clearly seeing letters and their order. These difficulties may be caused by abnormal development of their visual “magnocellular” (M) nerve cells; these mediate the ability to rapidly identify letters and their order because they control visual guidance of attention and of eye fixations. Evidence for M cell impairment has been demonstrated at all levels of the visual system: in the retina, in the lateral geniculate nucleus, in the primary visual cortex and throughout the dorsal visuomotor “where” pathway forward from the visual cortex to the posterior parietal and prefrontal cortices. This abnormality destabilises visual perception; hence, its severity in individuals correlates with their reading deficit. Treatments that facilitate M function, such as viewing text through yellow or blue filters, can greatly increase reading progress in children with visual reading problems. M weakness may be caused by genetic vulnerability, which can disturb orderly migration of cortical neurones during development or possibly reduce uptake of omega-3 fatty acids, which are usually obtained from fish oils in the diet. For example, M cell membranes require replenishment of the omega-3 docosahexaenoic acid to maintain their rapid responses. Hence, supplementing some dyslexics’ diets with DHA can greatly improve their M function and their reading.
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37
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Neural correlates of language and non-language visuospatial processing in adolescents with reading disability. Neuroimage 2014; 101:653-66. [PMID: 25067812 DOI: 10.1016/j.neuroimage.2014.07.029] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 06/17/2014] [Accepted: 07/18/2014] [Indexed: 01/08/2023] Open
Abstract
Despite anecdotal evidence of relative visuospatial processing strengths in individuals with reading disability (RD), only a few studies have assessed the presence or the extent of these putative strengths. The current study examined the cognitive and neural bases of visuospatial processing abilities in adolescents with RD relative to typically developing (TD) peers. Using both cognitive tasks and functional magnetic resonance imaging (fMRI) we contrasted printed word recognition with non-language visuospatial processing tasks. Behaviorally, lower reading skill was related to a visuospatial processing advantage (shorter latencies and equivalent accuracy) on a geometric figure processing task, similar to findings shown in two published studies. FMRI analyses revealed key group by task interactions in patterns of cortical and subcortical activation, particularly in frontostriatal networks, and in the distributions of right and left hemisphere activation on the two tasks. The results are discussed in terms of a possible neural tradeoff in visuospatial processing in RD.
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38
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Denison RN, Vu AT, Yacoub E, Feinberg DA, Silver MA. Functional mapping of the magnocellular and parvocellular subdivisions of human LGN. Neuroimage 2014; 102 Pt 2:358-69. [PMID: 25038435 DOI: 10.1016/j.neuroimage.2014.07.019] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Revised: 06/27/2014] [Accepted: 07/11/2014] [Indexed: 10/25/2022] Open
Abstract
The magnocellular (M) and parvocellular (P) subdivisions of primate LGN are known to process complementary types of visual stimulus information, but a method for noninvasively defining these subdivisions in humans has proven elusive. As a result, the functional roles of these subdivisions in humans have not been investigated physiologically. To functionally map the M and P subdivisions of human LGN, we used high-resolution fMRI at high field (7 T and 3 T) together with a combination of spatial, temporal, luminance, and chromatic stimulus manipulations. We found that stimulus factors that differentially drive magnocellular and parvocellular neurons in primate LGN also elicit differential BOLD fMRI responses in human LGN and that these responses exhibit a spatial organization consistent with the known anatomical organization of the M and P subdivisions. In test-retest studies, the relative responses of individual voxels to M-type and P-type stimuli were reliable across scanning sessions on separate days and across sessions at different field strengths. The ability to functionally identify magnocellular and parvocellular regions of human LGN with fMRI opens possibilities for investigating the functions of these subdivisions in human visual perception, in patient populations with suspected abnormalities in one of these subdivisions, and in visual cortical processing streams arising from parallel thalamocortical pathways.
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Affiliation(s)
- Rachel N Denison
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
| | - An T Vu
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Essa Yacoub
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - David A Feinberg
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA; Advanced MRI Technologies, Sebastopol, CA 95472, USA
| | - Michael A Silver
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA; School of Optometry, University of California, Berkeley, Berkeley, CA 94720, USA; Vision Science Graduate Group, University of California, Berkeley, Berkeley, CA 94720, USA
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Falkenberg HK, Simpson WA, Dutton GN. Development of sampling efficiency and internal noise in motion detection and discrimination in school-aged children. Vision Res 2014; 100:8-17. [PMID: 24732568 DOI: 10.1016/j.visres.2014.04.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 03/14/2014] [Accepted: 04/03/2014] [Indexed: 12/14/2022]
Abstract
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.
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Affiliation(s)
- Helle K Falkenberg
- Department of Optometry and Visual Science, Buskerud and Vestfold University College, Frogsvei 41, 3611 Kongsberg, Norway.
| | - William A Simpson
- School of Psychology, University of Plymouth, Drake Circus, Plymouth, Devon PL4 8AA, UK.
| | - Gordon N Dutton
- Department of Vision Sciences, Glasgow Caledonian University, 70 Cowcaddens Road, Glasgow G4 OAB, UK.
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Conlon EG, Lilleskaret G, Wright CM, Stuksrud A. Why do adults with dyslexia have poor global motion sensitivity? Front Hum Neurosci 2013; 7:859. [PMID: 24376414 PMCID: PMC3860316 DOI: 10.3389/fnhum.2013.00859] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 11/25/2013] [Indexed: 12/01/2022] Open
Abstract
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.
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Affiliation(s)
- Elizabeth G Conlon
- Griffith Health Institute, School of Applied Psychology, Griffith University Gold Coast, QLD, Australia
| | - Gry Lilleskaret
- Griffith Health Institute, School of Applied Psychology, Griffith University Gold Coast, QLD, Australia
| | - Craig M Wright
- Griffith Health Institute, School of Applied Psychology, Griffith University Gold Coast, QLD, Australia
| | - Anne Stuksrud
- Griffith Health Institute, School of Applied Psychology, Griffith University Gold Coast, QLD, Australia
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Abstract
Developmental dyslexia affects almost 10% of school-aged children and represents a significant public health problem. Its etiology is unknown. The consistent presence of phonological difficulties combined with an inability to manipulate language sounds and the grapheme-phoneme conversion is widely acknowledged. Numerous scientific studies have also documented the presence of eye movement anomalies and deficits of perception of low contrast, low spatial frequency, and high frequency temporal visual information in dyslexics. Anomalies of visual attention with short visual attention spans have also been demonstrated in a large number of cases. Spatial orientation is also affected in dyslexics who manifest a preference for spatial attention to the right. This asymmetry may be so pronounced that it leads to a veritable neglect of space on the left side. The evaluation of treatments proposed to dyslexics whether speech or oriented towards the visual anomalies remains fragmentary. The advent of new explanatory theories, notably cerebellar, magnocellular, or proprioceptive, is an incentive for ophthalmologists to enter the world of multimodal cognition given the importance of the eye's visual input.
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Affiliation(s)
- Patrick Quercia
- Department of Ophthalmology, University Hospital, Dijon, France
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PUGH KR, LANDI N, PRESTON JL, MENCL WE, AUSTIN AC, SIBLEY D, FULBRIGHT RK, SEIDENBERG MS, GRIGORENKO EL, CONSTABLE RT, MOLFESE P, FROST SJ. The relationship between phonological and auditory processing and brain organization in beginning readers. BRAIN AND LANGUAGE 2013; 125:173-83. [PMID: 22572517 PMCID: PMC3417084 DOI: 10.1016/j.bandl.2012.04.004] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 03/25/2012] [Accepted: 04/07/2012] [Indexed: 05/07/2023]
Abstract
We employed brain-behavior analyses to explore the relationship between performance on tasks measuring phonological awareness, pseudoword decoding, and rapid auditory processing (all predictors of reading (dis)ability) and brain organization for print and speech in beginning readers. For print-related activation, we observed a shared set of skill-correlated regions, including left hemisphere temporoparietal and occipitotemporal sites, as well as inferior frontal, visual, visual attention, and subcortical components. For speech-related activation, shared variance among reading skill measures was most prominently correlated with activation in left hemisphere inferior frontal gyrus and precuneus. Implications for brain-based models of literacy acquisition are discussed.
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Affiliation(s)
- Kenneth R. PUGH
- Haskins Laboratories, New Haven, CT
- Yale University School of Medicine, Department of Diagnostic Radiology
- University of Connecticut, Department of Psychology
| | - Nicole LANDI
- Haskins Laboratories, New Haven, CT
- Yale University Child Study Center
| | | | | | | | | | - Robert K. FULBRIGHT
- Haskins Laboratories, New Haven, CT
- Yale University School of Medicine, Department of Diagnostic Radiology
| | - Mark S. SEIDENBERG
- Haskins Laboratories, New Haven, CT
- University of Wisconsin, Madison, Department of Psychology
| | | | - R. Todd CONSTABLE
- Haskins Laboratories, New Haven, CT
- Yale University School of Medicine, Department of Diagnostic Radiology
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Martínez A, Revheim N, Butler PD, Guilfoyle DN, Dias EC, Javitt DC. Impaired magnocellular/dorsal stream activation predicts impaired reading ability in schizophrenia. Neuroimage Clin 2012; 2:8-16. [PMID: 24179753 PMCID: PMC3777659 DOI: 10.1016/j.nicl.2012.09.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 09/01/2012] [Accepted: 09/05/2012] [Indexed: 11/21/2022]
Abstract
In healthy humans, passage reading depends upon a critical organizing role played by the magnocellular/dorsal visual pathway. In a recent study, we found a significant correlation between orthographic reading deficits in schizophrenia and deficits in contrast sensitivity to low spatial frequency stimuli, suggesting an underlying magnocellular processing abnormality. The interrelationship between magnocellular dysfunction and passage reading impairments in schizophrenia was investigated in 21 patients with schizophrenia and 17 healthy control volunteers using behavioral and functional MRI (fMRI) based measures. fMRI activation patterns during passage- and single-word reading were evaluated in relation to cortical areas with differential sensitivity to low versus high spatial frequency cortical regions indentified using a phase-encoded fMRI paradigm. On average, patients with schizophrenia read at the 6th grade level, despite completion of more than 12 years of education and estimated normal pre-morbid IQ. Schizophrenia patients also showed significantly impaired contrast sensitivity to low spatial frequencies and abnormal neural activity in response to stimulation with low spatial frequencies, consistent with dysfunction of magnocellular processing. Further, these magnocellular deficits were predictive of poor performance on a standardized psychoeducational test of passage reading. These findings suggest that reading is an important index of cognitive dysfunction in schizophrenia and highlight the contribution of magnocellular dysfunction to overall cognitive impairments in schizophrenia.
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Affiliation(s)
- Antígona Martínez
- Nathan Kline Institute for Psychiatric Research, USA
- University of California, San Diego, USA
| | | | - Pamela D. Butler
- Nathan Kline Institute for Psychiatric Research, USA
- New York University Langone School of Medicine, USA
| | | | - Elisa C. Dias
- Nathan Kline Institute for Psychiatric Research, USA
| | - Daniel C. Javitt
- Nathan Kline Institute for Psychiatric Research, USA
- New York University Langone School of Medicine, USA
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Abrupt and ramped flicker-defined form shows evidence for a large magnocellular impairment in dyslexia. Neuropsychologia 2012; 50:2107-13. [PMID: 22609580 DOI: 10.1016/j.neuropsychologia.2012.05.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 04/18/2012] [Accepted: 05/11/2012] [Indexed: 11/21/2022]
Abstract
Controversy still exists over whether there is a magnocellular deficit associated with developmental dyslexia. Here we utilised a magnocellular system-biased phantom contour form discrimination task defined by high temporal frequency contrast reversals to compare contrast sensitivity in a group of children with dyslexia and an age- and nonverbal intelligence-matched control group (9-14 years). Stimuli were either abruptly presented for 4 refresh frames (34 ms), or in two reduced transience conditions had contrast progressively ramped on and off over either 4 frames or 10 frames (86 ms). Children in the dyslexia group showed increased contrast thresholds compared with the control group in all three conditions, and thus strong evidence for a magnocellular deficit. Although the absolute size of the differences in threshold scores between control and dyslexic groups increased dramatically between the abrupt and the 4 and 10 frame ramped onset stimuli, the similar effect size across all tasks, and also the similar range of contrast change at the first frame of stimulus presentation across all tasks between groups suggests that a similar neural mechanism could provide the locus of the apparent magnocellular deficit in children with dyslexia for all tasks tested. These results suggest that threshold discrimination of stimuli with low contrast and high temporal frequencies designed to target the magnocellular system, and has great potential for early screening for children at risk of visually derived reading difficulties.
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Wright CM, Conlon EG, Dyck M. Visual search deficits are independent of magnocellular deficits in dyslexia. ANNALS OF DYSLEXIA 2012; 62:53-69. [PMID: 22090158 DOI: 10.1007/s11881-011-0061-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 10/06/2011] [Indexed: 05/31/2023]
Abstract
The aim of this study was to investigate the theory that visual magnocellular deficits seen in groups with dyslexia are linked to reading via the mechanisms of visual attention. Visual attention was measured with a serial search task and magnocellular function with a coherent motion task. A large group of children with dyslexia (n = 70) had slower serial search times than a control group of typical readers. However, the effect size was small (η(p)(2) = 0.05) indicating considerable overlap between the groups. When the dyslexia sample was split into those with or without a magnocellular deficit, there was no difference in visual search reaction time between either group and controls. The data suggest that magnocellular sensitivity and visual spatial attention weaknesses are independent of one another. They also provide more evidence of heterogeneity in response to psychophysical tasks in groups with dyslexia. Alternative explanations for poor performance on visual attention tasks are proposed along with avenues for future research.
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Affiliation(s)
- Craig M Wright
- Behavioural Basis of Health Research Group, Griffith Health Institute, Griffith University, Gold Coast, QLD, Australia.
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Park SH, Kim SH, Cho YA, Joo CK. The Effect of Colored Filters in Patients with Meares-Irlen Syndrome. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2012. [DOI: 10.3341/jkos.2012.53.3.452] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Shin Hae Park
- Department of Ophthalmology and Visual Science, The Catholic University of Korea College of Medicine, Seoul, Korea
| | - Seung-Hyun Kim
- Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea
| | - Yoonae A Cho
- Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea
| | - Choun-Ki Joo
- Department of Ophthalmology and Visual Science, The Catholic University of Korea College of Medicine, Seoul, Korea
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Meng X, Cheng-Lai A, Zeng B, Stein JF, Zhou X. Dynamic visual perception and reading development in Chinese school children. ANNALS OF DYSLEXIA 2011; 61:161-176. [PMID: 21240572 DOI: 10.1007/s11881-010-0049-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2007] [Accepted: 11/19/2010] [Indexed: 05/30/2023]
Abstract
The development of reading skills may depend to a certain extent on the development of basic visual perception. The magnocellular theory of developmental dyslexia assumes that deficits in the magnocellular pathway, indicated by less sensitivity in perceiving dynamic sensory stimuli, are responsible for a proportion of reading difficulties experienced by dyslexics. Using a task that measures coherent motion detection threshold, this study examined the relationship between dynamic visual perception and reading development in Chinese children. Experiment 1 compared the performance of 27 dyslexics and their age- and IQ-matched controls in the coherent motion detection task and in a static pattern perception task. Results showed that only in the former task did the dyslexics have a significantly higher threshold than the controls, suggesting that Chinese dyslexics, like some of their Western counterparts, may have deficits in magnocellular pathway. Experiment 2 examined whether dynamic visual processing affects specific cognitive processes in reading. One hundred fifth-grade children were tested on visual perception and reading-related tasks. Regression analyses found that the motion detection threshold accounted for 11% and 12%, respectively, variance in the speed of orthographic similarity judgment and in the accuracy of picture naming after IQ and vocabulary size were controlled. The static pattern detection threshold could not account for any variance. It is concluded that reading development in Chinese depends to a certain extent on the development of dynamic visual perception and its underlying neural pathway and that the impact of visual development can be specifically related to orthographic processing in reading Chinese.
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Affiliation(s)
- Xiangzhi Meng
- Department of Psychology, Peking University, Beijing 100871, China
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48
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Denison RN, Silver MA. Distinct contributions of the magnocellular and parvocellular visual streams to perceptual selection. J Cogn Neurosci 2011; 24:246-59. [PMID: 21861685 DOI: 10.1162/jocn_a_00121] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
During binocular rivalry, conflicting images presented to the two eyes compete for perceptual dominance, but the neural basis of this competition is disputed. In interocular switch rivalry, rival images periodically exchanged between the two eyes generate one of two types of perceptual alternation: (1) a fast, regular alternation between the images that is time-locked to the stimulus switches and has been proposed to arise from competition at lower levels of the visual processing hierarchy or (2) a slow, irregular alternation spanning multiple stimulus switches that has been associated with higher levels of the visual system. The existence of these two types of perceptual alternation has been influential in establishing the view that rivalry may be resolved at multiple hierarchical levels of the visual system. We varied the spatial, temporal, and luminance properties of interocular switch rivalry gratings and found, instead, an association between fast, regular perceptual alternations and processing by the magnocellular stream and between slow, irregular alternations and processing by the parvocellular stream. The magnocellular and parvocellular streams are two early visual pathways that are specialized for the processing of motion and form, respectively. These results provide a new framework for understanding the neural substrates of binocular rivalry that emphasizes the importance of parallel visual processing streams, and not only hierarchical organization, in the perceptual resolution of ambiguities in the visual environment.
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Affiliation(s)
- Rachel N Denison
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720-3192, USA.
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Laycock R, Cross AJ, Lourenco T, Crewther SG. Dorsal stream involvement in recognition of objects with transient onset but not with ramped onset. Behav Brain Funct 2011; 7:34. [PMID: 21843368 PMCID: PMC3163526 DOI: 10.1186/1744-9081-7-34] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 08/16/2011] [Indexed: 12/03/2022] Open
Abstract
Background Although the ventral visual stream is understood to be responsible for object recognition, it has been proposed that the dorsal stream may contribute to object recognition by rapidly activating parietal attention mechanisms, prior to ventral stream object processing. Methods To investigate the relative contribution of the dorsal visual stream to object recognition a group of tertiary students were divided into good and poor motion coherence groups and assessed on tasks classically assumed to rely on ventral stream processing. Participants were required to identify simple line drawings in two tasks, one where objects were presented abruptly for 50 ms followed by a white-noise mask, the other where contrast was linearly ramped on and off over 325 ms and replaced with a mask. Results Although both groups only differed in motion coherence performance (a dorsal stream measure), the good motion coherence group showed superior contrast sensitivity for object recognition on the abrupt, but not the ramped presentation tasks. Conclusions We propose that abrupt presentation of objects activated attention mechanisms fed by the dorsal stream, whereas the ramped presentation had reduced transience and thus did not activate dorsal attention mechanisms as well. The results suggest that rapid dorsal stream activation may be required to assist with ventral stream object processing.
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Affiliation(s)
- Robin Laycock
- School of Psychological Science, La Trobe University, Melbourne, Australia.
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Tholen N, Weidner R, Grande M, Amunts K, Heim S. Eliciting dyslexic symptoms in proficient readers by simulating deficits in grapheme-to-phoneme conversion and visuo-magnocellular processing. DYSLEXIA (CHICHESTER, ENGLAND) 2011; 17:268-281. [PMID: 21793123 DOI: 10.1002/dys.434] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Among the cognitive causes of dyslexia, phonological and magnocellular deficits have attracted a substantial amount of research. Their role and their exact impact on reading ability are still a matter of debate, partly also because large samples of dyslexics are hard to recruit. Here, we report a new technique to simulate dyslexic symptoms in normal readers in two ways. Although difficulties in grapheme-to-phoneme conversion were elicited by manipulating the identifiability of written letters, visual-magnocellular processing deficits were generated by presenting letters moving dynamically on the screen. Both factors were embedded into a lexical word-pseudoword decision task with proficient German readers. Although both experimental variations systematically increased lexical decision times, they did not interact. Subjects successfully performed word-pseudoword distinctions at all levels of simulation, with consistently longer reaction times for pseudowords than for words. Interestingly, detecting a pseudoword was more difficult in the grapheme-to-phoneme conversion simulation as indicated by a significant interaction of word type and letter shape. These behavioural effects are consistent with those observed in 'real' dyslexics in the literature. The paradigm is thus a potential means of generating novel hypotheses about dyslexia, which can easily be tested with normal readers before screening and recruiting real dyslexics.
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Affiliation(s)
- Nicole Tholen
- Research Centre Jülich, Institute of Neurosciences and Medicine (INM-1 and INM-3), Germany
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