The word-length effect in acquired alexia, and real and virtual hemianopia
Highlights
► We examined the contribution of homonymous visual field loss to reading speed. ► We simulated hemianopia in healthy subjects with a gaze-contingent paradigm during an eye-tracking experiment. ► In healthy subjects, the 95% upper prediction limits were 51 ms/letter with full fields and 161 ms/letter with simulated right hemianopia. ► With these criteria, we examined six paradigmatic patients with acquired peripheral alexias. ► In these subjects, our findings clarified the magnitude of the word-length effect that originates from hemianopia alone.
Section snippets
Subjects
Thirteen healthy subjects participated (6 males, 7 females), with mean age of 37.9 years (standard deviation 9.2, range 25–54), All were right-handed except for one ambidextrous participant, and fluent in spoken and written English. The Institutional Review Boards of the University of British Columbia and Vancouver Hospital approved the protocol and all subjects gave informed consent in accordance with the principles of the Declaration of Helsinki.
We also tested six subjects with left or
Healthy subjects
The ANOVA showed a main effect of viewing condition on mean response time (F(2,24) = 21.1, p < 0.0001, Table 2). Tukey's HSD test showed a difference between full-field viewing and right or left hemianopia, with subjects requiring nearly twice as much time to read during virtual hemianopia, but no difference between right and left hemianopia. Mean response time with full-field viewing was correlated with mean response time under right hemianopic (r = 0.77, F(1,12) = 17.5, p < 0.0013) and left hemianopic
Discussion
Our data from healthy subjects show a modest word-length effect for both response times and number of fixations used for full-field viewing. Right or left virtual hemianopia approximately doubled mean response time and the word-length effect for both reading time and number of fixations. These data indicate that mean response times of up to 2100 ms (for a set of words of 3–9 letters) and word-length effects of up to 160 ms/letter can be attributed to the effects of complete right hemianopia
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Cited by (40)
The effects of simulated hemianopia on eye movements during text reading
2023, Vision ResearchRight hemi-alexia
2022, CortexCitation Excerpt :The impact of a small scotoma in the right central hemifield on reading has been recognized - for example, see case 90 in Barton et al., (2003). This has been called amblyopic dyslexia (Habekost et al., 2006), and can be considered a variant of right hemianopic dyslexia (Sheldon et al., 2012). One tachistoscopic study of amblyopic dyslexia showed that, as expected, the recognition difficulties in the right hemifield are non-specific.
Reading and alexia
2021, Handbook of Clinical NeurologyCitation Excerpt :It is unclear whether the word length effect in hemianopic alexia indicates a deficit in word processing, or whether it is purely due to the visual field defect. Sheldon et al. (2012) reported a study in healthy controls, which addressed this question by simulating a visual field defect in a gaze-contingent eye-tracking paradigm. They found that the simulated hemianopia caused a small word length effect, irrespective of whether the hemianopia was to the left (31 ms/letter) or right (38 ms/letter) of fixation.
Visual search for complex objects: Set-size effects for faces, words and cars
2019, Vision ResearchDo all visual deficits cause pure alexia? Dissociations between visual processing and reading suggest “no”
2018, Brain and CognitionCitation Excerpt :The anatomical basis of pure alexia has become clearer in the last fifteen years or so whereas the underlying cognitive deficit has remained a matter of debate (Behrmann, Nelson, & Sekuler, 1998; Habekost, Petersen, Behrmann & Starrfelt, 2014; Howard, 1991; Patterson & Kay, 1992; Patterson & Lambon Ralph, 1999; Yong, Warren, Warrington & Crutch, 2013). Speech production deficits cannot be held responsible, nor has the visual field defect, reported for the majority of pure alexic patients (Leff et al., 2001), been shown to cause the reading impairment (e.g., Bormann, Wolfer, Hachmann, Lagrèze, & Konieczny, 2014; Sheldon, Abegg, Sekunova & Barton, 2012). Since standard, paper-pencil based tests of visual processing were unaffected, Warrington and Shallice (1980) suggested that their participant suffered from ‘word-form dyslexia’, that is, impaired access to a visual lexicon (cf. Pflugshaupt et al., 2011).
Face perception in pure alexia: Complementary contributions of the left fusiform gyrus to facial identity and facial speech processing
2017, CortexCitation Excerpt :He had visual acuity of 20/25, normal color vision, and no visual field deficit. His mean reading time for single words was 847 msec, and his word-length effect 62 msec/letter, which is increased compared to 95% prediction limits of 40–50 msec/letter in subjects with full visual fields (Bao et al., 2015; Sheldon et al., 2012). He had a surface dysgraphia (e.g. CELLO = ‘chello’).