Too Little, Too Late: Reduced Visual Span and Speed Characterize Pure Alexia

Starrfelt, Randi; Habekost, Thomas; Leff, Alexander

doi:10.1093/cercor/bhp059

Cited by 95 publications

(90 citation statements)

References 62 publications

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“…This region, called the visual word form area (VWFA) (Cohen et al, 2000(Cohen et al, , 2002McCandliss et al, 2003), is shaped by reading experiences (Hashimoto and Sakai, 2004;Baker et al, 2007;Brem et al, 2010;Dehaene et al, 2010) and is not sensitive to low-level features of written words, such as size, position, font, or letter case (Dehaene et al, 2004;Binder et al, 2006;Vinckier et al, 2007;Glezer et al, 2009;Qiao et al, 2010;Braet et al, 2012). Neuropsychological studies have further revealed that the VWFA is necessary for reading, as the lesion of the VWFA is related to pure alexia with the hallmark feature of word-length effect (Mani et al, 2008;Pflugshaupt et al, 2009;Starrfelt et al, 2009). While extensive studies have focused on how the VWFA is tuned to visual properties of words, little is known about whether top-down influences modulate the VWFA.…”

Section: Introductionmentioning

confidence: 99%

Top-Down Processing of Symbolic Meanings Modulates the Visual Word Form Area

2012

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Functional magnetic resonance imaging (fMRI) studies on humans have identified a region in the left middle fusiform gyrus consistently activated by written words. This region is called the visual word form area (VWFA). Recently, a hypothesis, called the interactive account, is proposed that to effectively analyze the bottom-up visual properties of words, the VWFA receives predictive feedback from higherorder regions engaged in processing sounds, meanings, or actions associated with words. Further, this top-down influence on the VWFA is independent of stimulus formats. To test this hypothesis, we used fMRI to examine whether a symbolic nonword object (e.g., the Eiffel Tower) intended to represent something other than itself (i.e., Paris) could activate the VWFA. We found that scenes associated with symbolic meanings elicited a higher VWFA response than those not associated with symbolic meanings, and such top-down modulation on the VWFA can be established through short-term associative learning, even across modalities. In addition, the magnitude of the symbolic effect observed in the VWFA was positively correlated with the subjective experience on the strength of symbol-referent association across individuals. Therefore, the VWFA is likely a neural substrate for the interaction of the top-down processing of symbolic meanings with the analysis of bottom-up visual properties of sensory inputs, making the VWFA the location where the symbolic meaning of both words and nonword objects is represented.

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Section: Introductionmentioning

confidence: 99%

Top-Down Processing of Symbolic Meanings Modulates the Visual Word Form Area

2012

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“…In the pioneering study, Duncan et al (1999) showed how analysis of partial-and whole-report performance in terms of the parameters defined by TVA enables a very specific measurement of attention deficits in visual neglect patients (see also Bublak et al, 2005;. TVA-based assessment has now been used in studies of simultanagnosia (Duncan et al, 2003), integrative agnosia (Gerlach, Marstrand, Habekost & Gade, 2005), developmental dyslexia (Dubois et al, 2010), alexia (Habekost & Starrfelt, 2006;Starrfelt, Habekost & Gerlach, 2010;Starrfelt, Habekost & Leff, 2009), Huntington's disease (Finke et al, 2007), Alzheimer's disease (Bublak, Redel & Finke, 2006;Bublak et al, 2009;Redel et al, 2012), and the effects of stroke in particular parts of the brain (Habekost & Bundesen, 2003;Habekost & Rostrup, 2006, 2007Peers et al, 2005;see Habekost & Starrfelt, 2009, for a review). TVAbased assessment enables the estimation of parameters related to the span of VSTM (storage capacity of K objects), the rate of encoding into VSTM (processing capacity of C objects/s), the perceptual threshold (minimum effective exposure duration of t 0 ms), and the efficiency of selecting targets rather than distractors (selectivity α, defined as the attentional weight of a distractor divided by the attentional weight of a target).…”

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confidence: 99%

Sustained attention, attentional selectivity, and attentional capacity across the lifespan

McAvinue

Habekost

Johnson

et al. 2012

Atten Percept Psychophys

164

146

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Changes in sustained attention, attentional selectivity, and attentional capacity were examined in a sample of 113 participants between the ages of 12 and 75. To measure sustained attention, we employed the sustained-attention-to-response task (Robertson, Manly, Andrade, Baddeley, & Yiend, Neuropsychologia 35:747-58, 1997), a short continuousperformance test designed to capture fluctuations in sustained attention. To measure attentional selectivity and capacity, we employed a paradigm based on the theory of visual attention (Bundesen, Psychological Review 97:523-547, 1990), which enabled the estimation of parameters related to attentional selection, perceptual threshold, visual short-term memory capacity, and processing capacity. We found evidence of agerelated decline in each of the measured variables, but the declines varied markedly in terms of magnitude and lifespan trajectory. Variables relating to attentional capacity showed declines of very large effect sizes, while variables relating to attentional selectivity and sustained attention showed declines of medium to large effect sizes, suggesting that attentional control is relatively preserved in older adults. The variables relating to sustained attention followed a U-shaped, curvilinear trend, and the variables relating to attentional selectivity and capacity showed linear decline from early adulthood, providing further support for the differentiation of attentional functions.

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“…The role of the vWFA, which is consistently activated in reading studies, is still a matter of debate. While damage to this region can result in acquired alexia [51,52], there is evidence that such lesions do not produce alexia exclusively and may instead cause a more general deficit in simultaneous visual processing [53]. Moreover, vWFA has been shown to have resting-state functional correlations with regions in the dorsal attention network (left and right aIPS, MT?, and FEF regions) with minimal or absent correlations with reading-related regions.…”

Section: Discussionmentioning

confidence: 99%

Functional neural substrates of posterior cortical atrophy patients

2015

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Posterior cortical atrophy (PCA) is a neurodegenerative syndrome in which the most pronounced pathologic involvement is in the occipito-parietal visual regions. Herein, we aimed to better define the cortical reflection of this unique syndrome using a thorough battery of behavioral and functional MRI (fMRI) tests. Eight PCA patients underwent extensive testing to map their visual deficits. Assessments included visual functions associated with lower and higher components of the cortical hierarchy, as well as dorsal- and ventral-related cortical functions. fMRI was performed on five patients to examine the neuronal substrate of their visual functions. The PCA patient cohort exhibited stereopsis, saccadic eye movements and higher dorsal stream-related functional impairments, including simultant perception, image orientation, figure-from-ground segregation, closure and spatial orientation. In accordance with the behavioral findings, fMRI revealed intact activation in the ventral visual regions of face and object perception while more dorsal aspects of perception, including motion and gestalt perception, revealed impaired patterns of activity. In most of the patients, there was a lack of activity in the word form area, which is known to be linked to reading disorders. Finally, there was evidence of reduced cortical representation of the peripheral visual field, corresponding to the behaviorally assessed peripheral visual deficit. The findings are discussed in the context of networks extending from parietal regions, which mediate navigationally related processing, visually guided actions, eye movement control and working memory, suggesting that damage to these networks might explain the wide range of deficits in PCA patients.

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Too Little, Too Late: Reduced Visual Span and Speed Characterize Pure Alexia

Cited by 95 publications

References 62 publications

Top-Down Processing of Symbolic Meanings Modulates the Visual Word Form Area

Top-Down Processing of Symbolic Meanings Modulates the Visual Word Form Area

Sustained attention, attentional selectivity, and attentional capacity across the lifespan

Functional neural substrates of posterior cortical atrophy patients

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