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At least 19 recordsLinked to original sources
PubMed2005

Acquired dyslexia in a Turkish-English speaker.

The Turkish script is characterised by completely transparent bidirectional mappings between orthography and phonology. To date, there has been no reported evidence of acquired dyslexia in Turkish speakers leading to the naïve view that reading and writing problems in Turkish are probably rare. We examined the extent to which phonological impairment and orthographic transparency influence reading disorders in a native Turkish speaker. BRB is a bilingual Turkish-English speaker with deep dysphasia accompanied by acquired dyslexia in both languages. The main findings are an effect of imageability on reading in Turkish coincident with surface dyslexia in English and preserved nonword reading. BRB's acquired dyslexia suggests that damage to phonological representations might have a consequence for learning to read in Turkish. We argue that BRB's acquired dyslexia has a common locus in chronic underactivation of phonological representations in Turkish and English. Despite a common locus, reading problems manifest themselves differently according to properties of the script and the type of task.

Aged↗
PubMed1983

Phonological processes in reading: new evidence from acquired dyslexia.

This paper investigates the reading performance of two patients with acquired dyslexia. The first patient read aloud all classes of word (85-95 per cent correct), including affixed words, but failed to read aloud non-words. In addition, semantic judgments about written words were shown to be significantly impaired, relative to the ability to read the words aloud. These dissociations support the view that two independent lexical routes are available for reading aloud familiar words, a semantic route and a lexical phonological route. While unable to read aloud non-words, this patient retained the ability to segment orthographic and phonological stimuli. The reading of non-lexical material, therefore, does not appear to be mediated by lexical analogy procedures. Instead, it is suggested that a non-lexical phonological route exists that is clearly independent of lexical phonological procedures. This patient could process isolated written suffixes orthographically, but could only access complete phonological word forms. Suffixed words (but not isolated suffixes) appear to be represented in the phonological word store. The second patient read aloud non-words, but could not give phonetic sounds appropriate to single letters. This dissociation suggests that the reading aloud of non-words is not reliant upon grapheme-phoneme rules.

Aged↗
PubMed1987

The analysis of morphological errors in a case of acquired dyslexia.

An issue that is persistently raised in studies of subjects who produce morphological errors in reading and other tasks is whether these errors are the consequence of a morphological processing deficit, or whether they in any way reflect morphological principles of organization in the lexicon. We discuss the performance of one such subject on a number of tasks and evaluate standard arguments for attributing aspects of his performance to a morphological processing deficit. Although there are several features of his performance that are suggestive in this regard; we argue that, when these issues are addressed in the context of a sufficiently elaborated theory of lexical processing, a morphological processing deficit cannot be demonstrated. We also survey a number of recent reports that purport to provide evidence for a morphological processing deficit and argue that, in most cases, they fail to support such claims for similar reasons. An important moral to be drawn from a critique of these studies is that in order to make valid inferences concerning the role of morphology in organizing the lexicon, we must consider these errors in the context of theories of the lexicon that take seriously the effects of converging lexical factors in processing.

Adult↗
PubMed1999

Visual paralexias in a Spanish-speaking patient with acquired dyslexia: a consequence of visual and semantic impairments?

We report the case of a Spanish patient SC who misread 55 per cent of the single words shown to her. SC's reading accuracy was affected by word imageability and frequency. Nonword reading was very poor. The majority of SC's errors to real-word targets bore a close visual similarity to the items that elicited them, but there was no indication of an effect of serial position on the probability that a letter from a target word would be incorporated into the error made to that word. SC made some visual errors in object naming and also showed evidence of a general semantic impairment. We consider the similarity between SC and patient AB reported by Lambon Ralph and Ellis (1997), and suggest that the very high levels of visual errors shown by these two patients may reflect a combination of visual and semantic impairments.

Aged↗
PubMed1991

Lesioning an attractor network: investigations of acquired dyslexia.

A recurrent connectionist network was trained to output semantic feature vectors when presented with letter strings. When damaged, the network exhibited characteristics that resembled several of the phenomena found in deep dyslexia and semantic-access dyslexia. Damaged networks sometimes settled to the semantic vectors for semantically similar but visually dissimilar words. With severe damage, a forced-choice decision between categories was possible even when the choice of the particular semantic vector within the category was not possible. The damaged networks typically exhibited many mixed visual and semantic errors in which the output corresponded to a word that was both visually and semantically similar. Surprisingly, damage near the output sometimes caused pure visual errors. Indeed, the characteristic error pattern of deep dyslexia occurred with damage to virtually any part of the network.

Brain↗
PubMed2005

Whole-word phonological representations of disyllabic words in the Chinese lexicon: data from acquired dyslexia.

This study addresses the issue of the existence of whole-word phonological representations of disyllabic and multisyllabic words in the Chinese mental lexicon. A Cantonese brain-injured dyslexic individual with semantic deficits, YKM, was assessed on his abilities to read aloud and to comprehend disyllabic words containing homographic heterophonous characters, the pronunciation of which can only be disambiguated in word context. Superior performance on reading to comprehension was found. YKM could produce the target phonological forms without understanding the words. The dissociation is taken as evidence for whole-word representations for these words at the phonological level. The claim is consistent with previous account for discrepancy of the frequencies of tonal errors between reading aloud and object naming in Cantonese reported of another case study of similar deficits. Theoretical arguments for whole-word form representations for all multisyllabic Chinese words are also discussed.

Adult↗
PubMed2005

Letter-by-letter acquired dyslexia is due to the serial encoding of letters.

Letter-by-letter acquired dyslexia (pure alexia) is assumed to be related to the serial encoding of letters, but the evidence for this assumption is somewhat indirect. Here, we demonstrate that the deficit is indeed due to serial encoding by comparing the performance of a letter-by-letter dyslexic reader with the performance of normal readers who were forced to read letter by letter; the data patterns are remarkably similar.

Dyslexia, Acquired↗
PubMed1991

Modelling acquired dyslexia: a software tool for developing grapheme-phoneme correspondences.

In extending a computer model of acquired dyslexia, it has become necessary to develop a way to group printed characters in a word so that the character groups essentially have a one-to-one correspondence with the word's phonemes (speech sounds). This requires deriving a set of correspondences (legal character groupings, legal associations of character groups with phonemes, etc.) that yield a single grouping or "segmentation" of characters when applied to any English word. To facilitate and partially automate this task, a segmentation program has been developed that uses an interchangeable set of correspondences. The program segments words according to these correspondences and tabulates their success over large sets of words. The program has been used successfully to segment a 20,000 word corpus, demonstrating that this approach can be used effectively and efficiently.

Algorithms↗
PubMed2000

[Acquired dyslexias and dysgraphias under the prism of cognitive neuropsychology: a model for the Spanish language].

The present paper discusses the different clinical manifestations of acquired disorders of reading and writing from a neurocognitive viewpoint. Based on a specific functional architecture of reading and writing--a cognitive model; presented as well--the different syndromes of acquired dyslexias and dysgraphias, that have been described in the specialized literature during the last 25 years, will be reviewed. The different pathologies are distributed along three different functional axes: a plurimodal component, including the semantic system, for the description of peripheric disorders of reading and writing; a lexical block which is justified by the findings in patients with surface dyslexia/dysgraphia; and a third, sublexical component, in order to illustrate the different functional impairments in phonological dyslexia/dysgraphia. Following the description of syndromes due to selective "functional lesions", we discuss deep dyslexia/dysgraphia, a syndrome due to multiple functional lesions. All of the syndromes will be justified and discussed with respect to the different components of the functional architecture presented and are based on cases of the literature and personal observations. Concluding remarks will evaluate the new insights gained by the presented functional arquitecture in relation to other cognitive models for the analysis of reading aloud and writing to dictation of single words.

Agraphia↗
PubMed1994

Syndromes of acquired dyslexia and patterns of recovery: a 6- to 10-year follow-up study of seven brain-injured people.

Seven subjects who were neurologically impaired following encephalitis (n = 2), head injury (n = 3), and stroke (n = 2) were referred several years previously because of acquired dyslexia. Two were almost totally alexic, 2 were surface dyslexic, 2 were deep dyslexic and 1 was a letter-by-letter reader. Following a period of rehabilitation, the 2 with alexia became surface dyslexic and letter-by-letter readers; 1 of the deep dyslexics showed some improvements but remained a deep dyslexic; and the letter-by-letter reader learned to read more quickly. At follow-up, 6 to 10 years later, there had been little significant change. The 2 subjects whose alexia resolved into surface dyslexia with letter-by-letter reading had increased their reading ages but remained surface dyslexic and letter-by-letter readers. The subject who had been a letter-by-letter reader was faster at easier and more frequently used words but slower at harder, less frequently used words. Changes in the other 4 subjects were negligible. Implications for rehabilitation are discussed.

Adolescent↗
PubMed2000

Visuographemic alexia: a new form of a peripheral acquired dyslexia.

We report a single-case study of peripherally acquired dyslexia that meets the clinical criteria of "alexia without agraphia." The patient, AA, has a large infarct involving the left posterior cerebral artery. The most striking feature is a severe impairment in recognizing single visually presented letters that precludes explicit or implicit access to reading, even in a letter-by-letter fashion. AA can, however, differentiate letters from similar nonsense characters and digits, and he is also able to identify alphanumeric signs when the visual channel is bypassed (through somesthesic or kinesthesic presentation). Spelling tasks are also well performed. Since there is a breakdown in mapping a visually presented letter to its abstract graphemic representation, we propose the term "visuographemic alexia" for this kind of reading disorder. The pattern of deficits is interpreted following theoretical models previously developed in cognitive neuropsychology. An alexia for arabic numerals with preserved comprehension lends additional support for the crucial processing of different notational systems (e.g., phonographic vs logographic). More general perceptive disorders do not seem to account for these patterns; they are material-specific. Finally, we attempt to specify functional correlations with the implied neural networks.

Dominance, Cerebral↗
PubMed1986

Modelling reading aloud and its relevance to acquired dyslexia.

The cognitive processes underlying reading aloud are generally believed to involve a dual-route print-to-sound mapping. To test this idea, a parallel activation model of reading aloud is being implemented and subjected to experiments. Spread of activation in the model is based on a theory that competition between cognitive processes for limited neurophysiological resources is a fundamental organizing principle of memory retrieval. This paper briefly describes the dual-route print-to-sound mapping, introduces the competition-based theory being tested, and explains our work's relationship to modelling acquired dyslexia.

Artificial Intelligence↗
PubMed2000

Acquired dyslexia.

Disorders of reading are frequently encountered in patients with acquired cerebral lesions. Investigations in the past few decades have improved our understanding of these disorders. In this article we review the peripheral dyslexias, including neglect dyslexia, attentional dyslexia, and pure alexia (or alexia without agraphia), as well as the "central" dyslexias, including deep, surface, and phonological dyslexia. Current accounts of acquired dyslexia are also discussed. Finally, we briefly describe the reading tasks that serve to differentiate the different reading disorders.

Agraphia↗