Prominent effects and neural correlates of visual crowding in a neurodegenerative disease population

Yong, Keir X. X.; Shakespeare, Timothy J.; Cash, David M.; Henley, Susie M.D.; Nicholas, Jennifer M.; Ridgway, Gerard R.; Golden, Hannah L.; Warrington, Elizabeth K.; Carton, Amelia M.; Kaski, Diego; Schott, Jonathan M.; Warren, Jason D.; Crutch, Sebastian J.

doi:10.1093/brain/awu293

Cited by 35 publications

(50 citation statements)

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“…ReadClear was the treatment condition and consists on a software-based tool (app) designed following evidence-based principles of reading impairment and improvement in PCA [7,8,9,10] The app contains the following perceptual customizable options (settings), expected to mitigate PCA-related visual and oculomotor deficits: 1) a fixation box (Figure 2, A) aiming to limit visual disorientation and inspired by scrolling text paradigms and opposite contrast polarity, to minimize crowding risk [9,13]. This box could be fixed, minimizing the need to direct fixations vertically along the frontal plane.…”

Section: Treatmentmentioning

confidence: 99%

“…A Wilcoxon signed rank test assessed within-group differences. Nine exclusive categories of reading errors were identified: 1) words misread, 2) words misread and corrected, 3) omissions, 4) repetitions, 5) repetition of words misread, 6) additions, 7) approximations, 8) regressions in the text, 9) anticipations in the text. Regressions/anticipations were defined as words successfully read but in the wrong order in the text, resulting from returning/skipping forward to sections of the texts respectively.…”

Section: Outcome 2: Reading Accuracymentioning

confidence: 99%

“…The degree of reading impairment in PCA is influenced and modulated by perceptual variables. Previous investigations have provided evidence of people with PCA experiencing better recognition of single words when these are presented in smaller print and better recognition also of letters presented in isolation or flanked by stimuli of reverse contrast polarity [7,8,10]. In addition, recent studies of text reading have suggested that spatial factors are the primary determinant of reading accuracy in PCA and that reducing spatial demands may result in an increment of reading performance in this population [7,9].…”

Section: Introductionmentioning

confidence: 97%

“…The reading tool presented in this study, ReadClear, is an assistive reading app coproduced between our team and a group of people living with PCA. The app's design has been informed by previous evidence in the field [7][8][9][10][11] and allows customization of crucial perceptual properties of the text, intending to compensate for the following: visual disorientation (e.g. getting lost on the page), difficulties with oculomotor control (e.g.…”

Section: Introductionmentioning

confidence: 99%

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ReadClear: An Assistive Reading Tool for People Living with Posterior Cortical Atrophy

Suárez‐González

Ocal

Pavisic

et al. 2019

JAD

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word count: 215 Manuscript word count: 3908 Abstract Introduction: Progressive reading impairment is an early and debilitating symptom of posterior cortical atrophy (PCA) arising from the progressive deterioration of visual processing skills . The goal of this study was to test the effectiveness of a purposebuilt reading app (ReadClear) co-produced with people living with PCA and designed to reduce the reading difficulties experienced by this population (e.g. getting lost in the page and missing words when reading). . Method:Twenty subjects with PCA were included in a cross-over design home-based study aimed at determining whether ReadClear could 1) enhance the subjective reading experience (reading pleasantness) and 2) improve reading accuracy (reducing the number of reading errors) compared with a sham condition (a standard e-reader).Results: Reading using ReadClear provided a better subjective reading experience than sham (p= 0.018, d= 0.5) and significantly reduced the percentage of reading errors (p < 0.0001, r = 0.82), particularly errors due to omissions (p = 0.01, r = 0.50), repeated words (p = 0.002, r = 0.69) and regressions in the text (p = 0.003, r = 0.69). We found that different kinds of reading errors were related to specific neuropsychological profiles. Conclusions:ReadClear can assist reading in people living with PCA by reducing the number of reading errors and improving the subjective reading experience of users.

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Section: Treatmentmentioning

confidence: 99%

Section: Outcome 2: Reading Accuracymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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ReadClear: An Assistive Reading Tool for People Living with Posterior Cortical Atrophy

Suárez‐González

Ocal

Pavisic

et al. 2019

JAD

Self Cite

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“…Patients with PCA (whether or not named as such) are frequently used in neuroscientific investigations of a host of visual processes such as visual crowding (Yong et al, 2014), visual salience (Mannan et al, 2009;Foulsham et al, 2011), global/local processing and simultanagnosia (Graff-Radford et al, 1993;Coslett et al, 1995;Stark et al, 1997;Huberle et al, 2010;Thomas et al, 2012;Shakespeare et al, 2013) and letter-by-letter reading (Freedman et al, 1991;Price and Humphreys, 1995). Therefore a sound understanding of lower-order oculomotor function in these patients is critical for the accurate interpretation of such visuoperceptual and other impairments in patients with PCA.…”

Section: Introductionmentioning

confidence: 99%

Abnormalities of Fixation, Saccade and Pursuit in Posterior Cortical Atrophy

Shakespeare¹,

Kaski²,

Yong³

et al. 2015

J Neurol Neurosurg Psychiatry

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See Antoniades and Kennard (doi:10.1093/brain/awv124) for a scientific commentary on this article.The clinico-neuroradiological syndrome posterior cortical atrophy is the cardinal 'visual dementia' and most common atypical Alzheimer's disease phenotype, offering insights into mechanisms underlying clinical heterogeneity, pathological propagation and basic visual phenomena (e.g. visual crowding). Given the extensive attention paid to patients' (higher order) perceptual function, it is surprising that there have been no systematic analyses of basic oculomotor function in this population. Here 20 patients with posterior cortical atrophy, 17 patients with typical Alzheimer's disease and 22 healthy controls completed tests of fixation, saccade (including fixation/target gap and overlap conditions) and smooth pursuit eye movements using an infrared pupil-tracking system. Participants underwent detailed neuropsychological and neurological examinations, with a proportion also undertaking brain imaging and analysis of molecular pathology. In contrast to informal clinical evaluations of oculomotor dysfunction frequency (previous studies: 38%, current clinical examination: 33%), detailed eyetracking investigations revealed eye movement abnormalities in 80% of patients with posterior cortical atrophy (compared to 17% typical Alzheimer's disease, 5% controls). The greatest differences between posterior cortical atrophy and typical Alzheimer's disease were seen in saccadic performance. Patients with posterior cortical atrophy made significantly shorter saccades especially for distant targets. They also exhibited a significant exacerbation of the normal gap/overlap effect, consistent with 'sticky fixation'. Time to reach saccadic targets was significantly associated with parietal and occipital cortical thickness measures. On fixation stability tasks, patients with typical Alzheimer's disease showed more square wave jerks whose frequency was associated with lower cerebellar grey matter volume, while patients with posterior cortical atrophy showed large saccadic intrusions whose frequency correlated significantly with generalized reductions in cortical thickness. Patients with both posterior cortical atrophy and typical Alzheimer's disease showed lower gain in smooth pursuit compared to controls. The current study establishes that eye movement abnormalities are near-ubiquitous in posterior cortical atrophy, and highlights multiple aspects of saccadic performance which distinguish posterior cortical atrophy from typical Alzheimer's disease. We suggest the posterior cortical atrophy oculomotor profile (e.g. exacerbation of the saccadic gap/overlap effect, preserved saccadic velocity) reflects weak input from degraded occipito-parietal spatial representations of stimulus location into a superior collicular spatial map for eye movement regulation. This may indicate greater impairment of identification of oculomotor targets rather than generation of oculomotor movements. The results highlight the critical role of spatial attention an...

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Role of Population Receptive Field Size in Complex Visual Dysfunctions

et al. 2019

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The neuronal mechanism of visual agnosia and foveal crowding that underlies the behavioral symptoms of several classic neurodegenerative diseases, including impaired holistic perception, navigation, and reading, is still unclear. A better understanding of this mechanism is expected to lead to better treatment and rehabilitation.OBJECTIVE To use state-of-the-art neuroimaging protocols to assess a hypothesis that abnormal population receptive fields (pRF) in the visual cortex underlie high-order visual impairments.DESIGN, SETTING, AND PARTICIPANTS Between April 26 and November 21, 2016, patients and controls were recruited from the Hadassah-Hebrew University medical center in a cross-sectional manner. Six patients with posterior cortical atrophy (PCA) were approached and 1 was excluded because of an inability to perform the task. Participants underwent functional magnetic resonance imaging-based cortical visual field mapping and pRF evaluation and performed a masked repetition priming task to evaluate visuospatial perception along the eccentricity axis. The association between pRF sizes and behavioral impairments was assessed to evaluate the role of abnormal pRF sizes in impaired visual perception. Posterior cortical atrophy is a visual variant of Alzheimer disease that is characterized by progressive visual agnosia despite almost 20/20 visual acuity. Patients with PCA are rare but invaluable for studying visual processing abnormalities following neurodegeneration, as atrophy begins in visual cortices but initially spares other brain regions involved in memory and verbal communication.EXPOSURES Participants underwent a magnetic resonance imaging scan. MAIN OUTCOMES AND MEASURESPopulation receptive field sizes and their association with visual processing along the fovea-to-periphery gradient.RESULTS Five patients with PCA (4 men [80%]; mean [SEM] age, 62.9 [3.5] years) were compared with 8 age-matched controls (1 man [25%]; mean [SEM] age, 63.7 [3.7] years) and demonstrated an atypical pRF mapping that varied along the eccentricity axis, which presented as abnormally small peripheral and large foveal pRFs sizes. Abnormality was seen in V1 (peripheral, 4.4°and 5.5°; foveal, 5.5°and 4.5°in patients and controls, respectively; P < .05) as well as in higher visual regions, but not in intermediate ones. Behaviorally, an atypical fovea-to-periphery gradient in visual processing was found that correlated with their pRF properties (r = 0.8; P < .01 for the correlation between pRF and behavioral fovea-to-periphery slopes).CONCLUSIONS AND RELEVANCE High-order visuocognitive functions may depend on abnormalities in basic cortical characteristics. These results may fundamentally change approaches to rehabilitation in such conditions, emphasizing the potential of low-level visual interventions.

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Prominent effects and neural correlates of visual crowding in a neurodegenerative disease population

Cited by 35 publications

References 102 publications

ReadClear: An Assistive Reading Tool for People Living with Posterior Cortical Atrophy

ReadClear: An Assistive Reading Tool for People Living with Posterior Cortical Atrophy

Abnormalities of Fixation, Saccade and Pursuit in Posterior Cortical Atrophy

Role of Population Receptive Field Size in Complex Visual Dysfunctions

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