Bub, D. N., Arguin, M., & Lecours, A. R. (1993). Jules Dejerine and his interpretation of pure alexia. Brain and Language, 45, 531-559.
Dejerine's interpretation of pure alexia is routinely mentioned in all neuropsychological textbooks, yet the details of his account and the evidence on which it is based have never been subjected to a critical analysis. We provide such an evaluation in this paper, summarizing the behavioral data that Dejerine presented in his now famous case report and the theoretical framework he adopted to explain the phenomenon of alexia without agraphia. We also provide a link between Dejerine's work and current hypotheses on the nature of the syndrome

AD: Montreal Neurological Institute, Quebec, Canada AB




Dan Bub


Dan Bub has contributed to the study of the alexias for a long time  -  Selected alexia references:

Bub, D., Cancelliere, A., & Kertesz, A. (1985). Whole-word and analytic translation of spelling to sound in a non-semantic reader. In K.E.Patterson, J. C. Marshall, & M. Coltheart (Eds.), Surface dyslexia: Neuropsychological and cognitive studies of phonological reading (pp. 15-34). London: Erlbaum.

Bub, D. N., Black, S., & Howell, J. (1989). Word recognition and orthographic context effects in a letter-by- letter reader. Brain and Language, 36, 357-376.
Notes: Montreal Neurological Institute, Quebec, Canada The performance of letter-by-letter readers when attempting to decipher written material gives the impression that words fail to directly evoke any higher-level representation. As a consequence, spelling patterns appear to be treated perceptually as if they were a collection of random letters. We tested the hypothesis that words are no longer mapped onto orthographic descriptions by examining the ability of a letter-by-letter reader to identify letters in familiar words, pseudowords, and random strings. A clear effect of orthographic context was obtained on the accuracy of letter recognition, indicating that spelling patterns do gain access to more central components of the reading mechanism. The implications of this result for our understanding of the syndrome are discussed

Behrmann, M., Black, S. E., & Bub, D. (1990). The evolution of pure alexia: a longitudinal study of recovery. Brain and Language, 39, 405-427.
Notes: Department of Psychology, University of Toronto, Ontario, Canada This case report documents the partial recovery, over a 12-month period, of pure alexia in an adult female following a left occipital infarction. Measures of speed and accuracy were obtained on an oral reading and a lexical decision task immediately postonset and then on 10 subsequent occasions. Explicit letter-by-letter reading was observed only during the first week poststroke but a significant effect of word length was seen in all testing sessions. Reading accuracy was relatively good at all stages and reading latency showed a remarkable decrease over time but did not reach normal reading rates. The inability to use higher-order orthographic knowledge, as manifest in the absence of a word superiority effect, was still noted at one year postonset. We therefore concluded that the change in behavior was attributable to increased proficiency in the use of the adaptive letter-by-letter procedure rather than to the resolution of the underlying deficit. It is suggested that longitudinal neurobehavioral studies add to our understanding of the alexic deficit and provide insight into the recovery process

Behrmann, M. & Bub, D. (1992). Surface dyslexia and dysgraphia: Dual routes, single lexicon. Cognitive Neuropsychology, 9, 209-251.
Notes: The dual route interpretation of surface dyslexia as a deficit in word-specific activation has been challenged recently by computational models that incorporate a unitary print-to-sound mechanism. The most current of these makes no allowance for word-specific nodes, but obtains the pronounciation of regular and exception words by weighted connections between graphemic and phonemic units. Damaging the model in a variety of ways produces a pattern that appears consistent with the performance of many surface dyslexic patients. Exception words are mispronounced more often than regular words, though accuracy deteriorates on both categories. In addition, frequency has no clear-cut effect on the probability of reading an exception word correctly. We describe the existence of a variant of the syndrome that is not fully captured by the above simulations. MP, a surface dyslexic, demonstrates a dissociation between lexical and nonlexical pronounciation of written words. We also show that performance on irregular words varies as a function of their frequency. We provide evidence that the locus of the subject's deficit arises at the level of the representations in a single orthographic lexicon that subserves both reading and writing

Arguin, M. & Bub, D. N. (1993). Single-character processing in a case of pure alexia. Neuropsychologia, 31, 435-458.
Notes: Montreal Neurological Institute, Quebec, Canada The processing of single characters in a pure alexic patient was studied in an attempt to identify the impairment responsible for his reading disorder. Observations from Experiments 1 to 4 suggested a deficit of identification of alphanumeric stimuli without any impairment affecting the elaboration of a structural description of visual stimulation. Experiment 5 indicated that the identification disorder results from a defect in the selective processes--activation and/or inhibition--that must come into play for achieving an appropriate match between a structural description of the stimulation and representations of the identities of known stimuli. The possible implications of this deficit in single-character identification for word reading are discussed

Arguin, M. & Bub, D. N. (1994). Functional mechanisms in pure alexia: Evidence from letter processing. In M.J.Farah & G. Ratcliff (Eds.), The neuropsychology of high-level vision. Collected tutorial essays (pp. 149-171). Hillsdale,NJ: Erlbaum.

Arguin, M. & Bub, D. N. (1994). Pure alexia: attempted rehabilitation and its implications for interpretation of the deficit. Brain and Language, 47, 233-268.
Notes: AD: Departement de psychologie, Universite de Montreal, Quebec, Canada AB: On the basis of data indicating the failure to encode letters as abstract orthographic identities in a pure alexic patient (D.M.) coupled with hypotheses about the effect of such a failure on word reading, an attempt at changing the nature of letter processing in D.M. was conducted. The training procedures failed to produce any fundamental change in the operations used by D.M. to encode isolated letters or words. However, rapid and massive benefits occurred in the overall speed of reading as a result of the training program. These appear to result from an increased rate of letter identification and the faster integration of individual letters into letter combinations. The observations gathered throughout this rehabilitation attempt provided evidence which constrains the range of possible explanations for the characteristic features of pure alexia. It is proposed that the letter-by-letter reading procedure which is the hallmark of the disorder may follow from an incapacity to directly encode visual letters as abstract orthographic types

Bub, D. N. & Arguin, M. (1995). Visual word activation in pure alexia. Brain and Language, 49, 77-103.
Notes: Montreal Neurological Institute, Canada A patient with pure alexia (DM) is shown to perform rapid and accurate lexical decisions for common words without the ability to recover their complete identity. We provide evidence using a speeded decision task that DM is not forced to rely on a laborious analysis of individual letter forms when judging the lexical status of orthographic patterns varying in length, though he clearly must use this approach to fully identify a word for explicit report. By contrast, the ability to rapidly classify a word apparently does not extend to judgements of its superordinate category. DM makes semantic decisions for visual words by adopting the same inefficient procedure he uses for verbal report of their identity. The results provide further constraints on the functional deficit responsible for pure alexia. We argue that DM is able to monitor the overall activation of word units without achieving full identification and that such a process may be a characteristic of the normal reading mechanism

Bowers, J. S., Arguin, M., & Bub, D. N. (1996). Fast and specific access to orthographic knowledge in a case of letter-by-letter surface alexia. Cognitive Neuropsychology, 13, 525-567.
Notes: A series of experiments assessed priming for single letters and words in a letter-by-letter reader (IH) when primes were displayed briefly (between 100-500 msec) and masked. Consistent with previous claims that letter-by-letter readers have difficulties accessing orthographic letter codes, IH failed to show normal cross-case priming for single letters in a naming task (e.g., a/A ). Nevertheless, IH showed robust cross-case priming for four-letter words that have few if any perceptual features in common between upper and lower case (e.g. read/READ ; the letters r/R, e/E, a/A , and d/D are visually dissimilar in lower/upper case), even at prime durations that failed to support priming for single letters. Furthermore, priming extended to pseudowords (e.g. DEAT ), and was highly specific given that no priming was obtained between orthographic neighbors (e.g. face did not prime FACT). Based on this pattern of results, we argue that IH gains relatively normal access to orthographic representations, and that his letter-by-letter reading reflects a partial disconnection between orthographic and phonological representations. Within the context of a disconnection account, we provide an explanation of the paradoxical finding of robust word priming in the absence of single letter priming

Bowers, J. S., Bub, D. N., & Arguin, M. (1996). A characterisation of the word superiority effect in a case of letter-by-letter surface alexia. Cognitive Neuropsychology, 13, 415-441.

Bub, D. N. (1996). Dyslexia. In J.G.Beaumont, P. M. Kenealy, & M. J. C. Rogers (Eds.), The Blackwell dictionary of neuropsychology (pp. 291-300). Oxford: Blackwell.
Notes: (Paperback 1999)

Arguin, M., Fiset, S., & Bub, D. (2002). Sequential and parallel letter processing in letter-by-letter dyslexia. Cognitive Neuropsychology, 19, 535-555.
Notes: Dr. M. Arguin, Departement de Psychologie, Universite de Montreal, Succ. Centre-ville, Montreal, Que. H3C 3J7, Canada
Four experiments are reported that focus on the issue of sequential vs. parallel letter processing in letter-by-letter (LBL) dyslexia; these were conducted on patient III. Expt. 1 showed a large linear reduction of word naming times with an increase in the number of orthographic neighbours of the target (i.e., words of the same length differing by just one letter; N size). Given the large negative linear correlation existing between word length and N size, this result raises the possibility that the large word length effect diagnostic of LBL dyslexia may be, in fact, an artefact of uncontrolled N size. Expt. 2 falsified this possibility by showing that the word length effect is unaffected by whether N size is controlled for or not. This result also suggested that the facilitatory effect of increased N size in LBL dyslexia is based on the parallel processing of the constituent letters of the target. Further supporting a contribution of parallel letter processing to overt word recognition performance in the disorder, Expt. 3 showed significant but independent effects of word length and letter confusability (i.e., similarity of the constituent letters of the target word with other letters of the alphabet). The letter confusability effect therefore appears to rest on the parallel analysis of the letters in the target word. Finally, Expt. 4 showed that the facilitatory effect of N size is prevented with high letter-confusability targets. These observations suggest that LBL dyslexia rests on an impairment of letter encoding that results in an excessive level of background noise in the activation of lexical-orthographic representations when letters are processed in parallel. This prevents overt identification of the target and forces sequential letter processing in order to achieve this goal

Bub, D. (2003). Alexia and related reading disorders. Neurologic Clinics, 21, 549-568.
Notes: Department of Psychology, Faculty of Social Sciences, University of Victoria, Victoria, BC V8W 3P5, Canada. dbub@uvic.ca
Peripheral dyslexias are the result of impairment to processes that convert letters on the page into an abstract orthographic representation. Many aspects of these disorders are difficult to understand in depth. Invariably, there is evidence that some type of word-level perception occurs rapidly in many patients with LBL reading or neglect dyslexia, yet apparently contradictory evidence indicates that part of the word has been misperceived or that the letters must be analyzed laboriously for conscious identification to occur. Current theories attempt to synthesize these different aspects of the patients' performance, but their development is at an early stage. Questions remain also about the domain specificity of the perceptual impairment in LBL reading and about the nature of spatial attention and spatial frames in neglect dyslexia and other forms of attentional disorder. Current understanding of central dyslexias has perhaps advanced further. Well-developed computational models exist of these dyslexias, as do plausible experimental techniques for revealing the activity of semantic and non-semantic routes in normal readers. Nevertheless, the difficult issue of domain specificity arises again with respect to some of the mechanisms invoked, and in this regard, central and peripheral dyslexias continue to pose the same challenge

Arguin, M. & Bub, D. (2005). Parallel processing blocked by letter similarity in letter-by-letter dyslexia: A replication. Cognitive Neuropsychology, 22, 589-602.
Notes: Dr. M. Arguin, Departement de Psychologie, Universite de Montreal, Succ. Centre-ville, Montreal, Que. H3C 3J7
An investigation of the joint effects of orthographic neighbourhood size (N size) and of letter confusability in three letter-by-letter (LBL) dyslexics is reported. All three patients showed a facilitatory effect of increased N size with low letter-confusability words, but no N size effect with high confusability words. This exactly replicates previous observations by Arguin, Fiset, and Bub (2002) in another LBL dyslexic. A facilitatory N size effect requires parallel letter processing and the word recognition performance of normal readers is unaffected by letter confusability. The present findings therefore signal that the residual capacity for parallel letter processing in LBL dyslexic is blocked by letter similarity. This implies a deficit of letter encoding or identification, which appears to be a general feature of LBL dyslexia since it is exhibited by all of the four patients so tested.

Fiset, D., Arguin, M., Bub, D., Humphreys, G. W., & Riddoch, M. J. (2005). How to make the word-length effect disappear in letter-by-letter dyslexia: implications for an account of the disorder. Psychological Science, 16, 535-541.
Notes: Centre de Recherche en Neuropsychologie et Cognition, Departement de Psychologie, Universite de Montreal, CP 6128, Succ. Centre-ville, Montreal, Quebec H3C 3J7, Canada
The diagnosis of letter-by-letter (LBL) dyslexia is based on the observation of a substantial and monotonic increase of word naming latencies as the number of letters in the stimulus increases. This pattern of performance is typically interpreted as indicating that word recognition in LBL dyslexia depends on the sequential identification of individual letters. We show, in 7 LBL patients, that the word-length effect can be eliminated if words of different lengths are matched on the sum of the confusability (visual similarity between a letter and the remainder of the alphabet) of their constituent letters. Additional experiments demonstrate that this result is mediated by parallel letter processing and not by any compensatory serial processing strategy. These findings indicate that parallel processing contributes significantly to explicit word recognition in LBL dyslexia and that a letter-processing impairment is fundamental in causing the disorder

Fiset, D., Blais, C., Arguin, M., Tadros, K., Ethier-Majcher, C., Bub, D. et al. (2009). The spatio-temporal dynamics of visual letter recognition. Cognitive Neuropsychology, 26, 23-35.
Notes: We applied the Bubbles technique to reveal directly the spatio-temporal features of uppercase Arial letter identification. We asked four normal readers to each identify 26,000 letters that were randomly sampled in space and time; afterwards, we performed multiple linear regressions on the participant's response accuracy and the space-time samples. We contend that each cluster of connected significant regression coefficients is a letter feature. To bridge the gap between the letter identification literature and this experiment, we also determined the relative importance of the features proposed in the letter identification literature. Results show clear modulations of the relative importance of the letter features of some letters across time, demonstrating that letter features are not always extracted simultaneously at constant speeds. Furthermore, of all the feature classes proposed in the literature, line terminations and horizontals appear to be the two most important for letter identification
University of Victoria, Victoria, British Columbia, Canada

Anders Gade