Prelexical representations and processes in reading: Evidence from acquired dyslexia

Abstract

We report a detailed and extensive single-case study of an acquired dyslexic patient, L.H.D., who suffered a left-hemisphere lesion as a result of a ruptured aneurysm. We present evidence that L.H.D.'s reading errors stem from a deficit in visual letter identification, and we use her deficit as a basis for exploring a variety of issues concerning prelexical representations and processes in reading. First, building on the work of other researchers, we present evidence that the prelexical reading system includes an allograph level of representation that represents each distinct visual shape of a letter (e.g., a, A, etc., for the letter A). We extend a theory proposed by Caramazza and Hillis [Caramazza, A., & Hillis, A. (1990a). Spatial representation of words in the brain implied by studies of a unilateral neglect patient. Nature, 346, 267-269] to include an allograph level, and we probe the nature of the allograph representations in some detail. Next, we explore the implications of visual similarity effects and letter perseverations in L.H.D.'s reading performance, arguing that these effects shed light on activation dynamics in the prelexical reading system and on the genesis of L.H.D.'s errors. We also probe the processing of letter case in the visual letter identification process, proposing that separate abstract letter identity and case representations are computed. Finally, we present evidence that the allograph level as well as the abstract letter identity level implement a word-based frame of reference.

Beyond the visual word form area: The orthography–semantics interface in spelling and reading

“…As would be expected given this deficit locus, DSN exhibited the signs of the lexical orthographic impairment in the task of recognition of oral spelling in which she showed abnormal performance with low frequency and irregular words and produced regularization errors, just as she did in oral reading of the same words when presented visually. LHD, in contrast, other than the pre-lexical difficulties that have been documented by McCloskey & Schubert (McCloskey & Schubert, 2013, this issue; Schubert & McCloskey, 2013), showed no evidence of additional disruption to the reading system. Her pre-lexical difficulties quite naturally disrupted reading of words and nonwords presented visually but her recognition of oral spelling was strikingly intact and provided clear evidence of the integrity of the lexical orthographic processes and representations used for reading.…”

“…McCloskey and Schubert (McCloskey & Schubert, 2013, this issue; Schubert & McCloskey,2013) proposed that LHD suffered from a deficit in pre-lexical processing that left intact her ability to process the visual forms of letters but specifically disrupted her ability to map between visual representations of letter shapes and their abstract identities. 3 Note that the evidence presented indicates that abstract letter representations are intact, and what is disrupted is access to them from visual input.…”

“…The tasks of recognition of oral spelling and reading were administered to DSN and LHD and a group of 8 age-matched controls (see McCloskey & Schubert, 2013, this issue; Schubert & McCloskey, 2013). DPT was not tested on recognition of oral spelling but DSN was administered a list of 90 words that varied in frequency and regularity and LHD was administered a list of 92 words varying in frequency (the list was administered 5 times for reading and once for recognition of oral spelling).…”

Recognition of oral spelling is diagnostic of the central reading processes

“…Images of L.H.D. 's lesion and additional case history information can be found inSchubert and McCloskey (2013; also McCloskey, Fischer- Baum, & Schubert, 2013;McCloskey & Schubert, 2014).…”

The independence of letter identity and letter doubling in reading

“…The lack of a distractor-word lexicality effect in Experiment 1 implicates prelexical representations but visual word recognition has been argued to rely on several levels of prelexical letter representation. Schubert and McCloskey (2013) propose a distinction between an allographic level that represents distinct visual shapes of letter and an abstract identity letter level that abstracts away from visual properties like case and font. Based on the current work, either level could be the locus of the effect.…”