Covert reading of letters in a case of global alexia

Abstract

We would like to dedicate this work to the memory of Lamberto Piron Keywords:Global alexia Abstract letter identification Right hemisphere contribution to word reading a b s t r a c t This study describes the case of a global alexic patient with a severe reading deficit affecting words, letters and Arabic numbers, following a left posterior lesion. The patient (VA) could not match spoken letters to their graphic form. A preserved ability to recognize shape and canonical orientation of letters indicates intact access to the representation of letters and numbers as visual objects. A relatively preserved ability to match lowercase to uppercase letters suggests partially spared access to abstract letter identities independently of their visual forms. The patient was also unable to match spoken letters and numbers to their visual form, indicating that she could not access the graphemic representations of letters from their phonological representations. This pattern of performance suggests that the link between graphemic and phonological representations is disrupted in this patient. We hypothesize that VA' residual reading abilities are supported by the right hemisphere.

Exploring the neural correlates of the reversed letter effect: Evidence from left and right parietal patients

“…Indeed, our LPpt showed spared reading ability; they could explicitly recognize letters and correctly discriminate among their mirror-reversal. This is in line with some cases of global alexia documenting that patients can still recognize the letter shape and canonical orientation of letters in paper and pencil tasks measuring accuracy indicating intact access to the representation of letters [30][31]. Measuring RTs, we found a lack of interference exerted by the letter in a canonical view.…”

Prelexical representations and processes in reading: Evidence from acquired dyslexia

“…As we have noted, a number of previous studies have also reported dissociations between letter identification and letter decision tasks (e.g., Brunsdon et al, 2006;Caplan & Hedley-Whyte, 1974;Chanoine et al, 1998;Dalmás & Dansilio, 2000;Miozzo & Caramazza, 1998;Volpato et al, 2012). These studies have interpreted the dissociation as evidence for a distinction between an allograph level of representation and a level of abstract letter identity representations (see also Rapp & Caramazza, 1989).…”

“…Several recent reports have described patients who are impaired at letter identification, yet nevertheless are able to distinguish real letters from other characters such as pseudoletters or misoriented letters (e.g., Brunsdon et al, 2006;Caplan & Hedley-Whyte, 1974;Chanoine et al, 1998;Dalmás & Dansilio, 2000;Miozzo & Caramazza, 1998;Volpato et al, 2012). We demonstrate that L.H.D.…”

“…is intact in generating visual feature map and character shape representations from visual stimuli, these levels do not distinguish the learned shapes of real letters from the novel shapes of pseudoletters. Prior studies reporting dissociations between intact letter decision and impaired letter identification (e.g., Brunsdon et al, 2006;Caplan & HedleyWhyte, 1974;Chanoine et al, 1998;Dalmás & Dansilio, 2000;Miozzo & Caramazza, 1998;Volpato et al, 2012) have interpreted the phenomena as evidence for an allograph level that represents the various distinct shapes (e.g., A vs. a) for each letter (see also Rapp & Caramazza, 1989).…”

“…On the basis of the results, as well as findings from previous studies, we propose several significant elaborations and extensions of the Hillis (1990a, 1990b) theory. First, we build upon a growing body of work (e.g., Brunsdon, Coltheart, & Nickels, 2006;Caplan & Hedley-Whyte, 1974;Chanoine, Teixeira Ferreira, Demonet, Nespoulous, & Poncet, 1998;Dalmás & Dansilio, 2000;Miozzo & Caramazza, 1998;Rapp & Caramazza, 1989;Volpato, Bencini, Meneghello, Piron, & Semenza, 2012) that demonstrates the need to posit a level of representation not included in the original Caramazza and Hillis theory: an allograph level that represents each distinct visual form of a letter (e.g., g and G for the letter G). As well as showing that L.H.D.…”