The anatomical foundations of acquired reading disorders: a neuropsychological verification of the dual-route model of reading.

In this study we investigated the neural correlates of acquired reading disorders through an anatomo-correlative procedure of the lesions of 59 focal brain damaged patients suffering from acquired surface, phonological, deep, undifferentiated dyslexia and pure alexia. Two reading tasks, one of words and nonwords and one of words with unpredictable stress position, were used for this study. We found that surface dyslexia was predominantly associated with left temporal lesions, while in phonological dyslexia the lesions overlapped in the left insula and the left inferior frontal gyrus (pars opercularis) and that pure alexia was associated with lesions in the left fusiform gyrus. A number of areas and white matter tracts, which seemed to involve processing along both the lexical and the sublexical routes, were identified for undifferentiated dyslexia. Two cases of deep dyslexia with relatively dissimilar anatomical correlates were studied, one compatible with Coltheart's right-hemisphere hypothesis (1980) whereas the other could be interpreted in the context of Morton and Patterson's (1980), multiply-damaged left-hemisphere hypothesis. In brief, the results of this study are only partially consistent with the current state of the art, and propose new and stimulating challenges; indeed, based on these results we suggest that different types of acquired dyslexia may ensue after different cortical damage, but white matter disconnection may play a crucial role in some cases.

Connectionist neuropsychology: uncovering ultimate causes of acquired dyslexia.

Acquired dyslexia offers a unique window on to the nature of the cognitive and neural architecture supporting skilled reading. This paper provides an integrative overview of recent empirical and computational work on acquired dyslexia within the context of the primary systems framework as implemented in connectionist neuropsychological models. This view proposes that damage to general visual, phonological or semantic processing abilities are the root causes of different forms of acquired dyslexia. Recent case-series behavioural evidence concerning pure alexia, phonological dyslexia and surface dyslexia that supports this perspective is presented. Lesion simulations of these findings within connectionist models of reading demonstrate the viability of this approach. The commitment of such models to learnt representations allows them to capture key aspects of performance in each type of acquired dyslexia, particularly the associated non-reading deficits, the role of relearning and the influence of individual differences in the premorbid state of the reading system. Identification of these factors not only advances our understanding of acquired dyslexia and the mechanisms of normal reading but they are also relevant to the complex interactions underpinning developmental reading disorders.

Optokinetic stimulation affects word omissions but not stimulus-centered reading errors in paragraph reading in neglect dyslexia.

Patients with right hemisphere lesions often omit or misread words on the left side of a text or the initial letters of single words, a phenomenon termed neglect dyslexia (ND). Omissions of words on the contralesional side of the page are considered as egocentric or space-based errors, whereas misread words can be viewed as a type of stimulus-centered error where the left part of a single perceptual entity (the word) is neglected. Previous patient studies have shown that optokinetic stimulation (OKS) significantly modulates many facets of the neglect syndrome, including the subjective body midline, line bisection and size distortions. An open question is whether OKS can also influence omissions and stimulus-centered errors in paragraph reading in ND. The current study compared the influence of OKS on both types of reading errors using controlled indented paragraph reading tests in a group of 9 right-hemisphere lesioned patients with ND, 7 patients without ND and 9 matched healthy controls. Leftward OKS significantly reduced omissions on the left side of the text in ND. In contrast, the pattern of stimulus-centered reading errors remained unchanged. In conclusion egocentric manipulations like OKS only appear to influence space-based attentional processes evident as omissions in paragraph reading but have no impact on stimulus-centered attentional processes evident as word-based errors during paragraph reading in ND.

Treatment of reading impairment after stroke.

PURPOSE OF REVIEW: Reading impairments after left or right hemisphere stroke are common yet receive little attention from clinicians and therapists. In this review, we focus on the classification of acquired alexia and the current theory and practice underlying the rehabilitation of this diverse set of disorders. RECENT FINDINGS: The underlying behavioural impairments that dictate reading ability in the acquired alexias are becoming better understood; this, in turn, has led to targeted therapies being undertaken, mainly on a single subject basis. In hemianopic alexia, the most 'peripheral' of the acquired alexias, where text reading speed is determined largely by damage to the visual field, therapies have been directed at improving reading eye movements. In 'pure' alexia, techniques are usually aimed at improving whole-word recognition. In central alexic syndromes, where other language functions are also involved, the emphasis has been on strengthening connections between lexical and semantic representations, strengthening phonological representations, or both, and their association with lexical/semantic knowledge. SUMMARY: Despite targeted approaches to the rehabilitation of patients with alexia caused by stroke, there is still a preponderance of largely descriptive, single-case studies in the literature. In some syndromes, small trials have been attempted and the hope is that, in the future, more systematic investigations will be carried out so rehabilitation efforts can be built on a strong theoretical and empirical foundation. Well designed, single-case studies continue to play an important role in informing therapy, as these disorders are, by nature, heterogeneous.

[Peripheral alexias]. / Alexiile periferice.

The brain lesions could lead to impairments of the comprehension and production of written language. This acquired inability is named alexia. It is a significant problem for neurologists and ophthalmologists. Our study presents a classification of the alexias, whose pathology was describe first by Dejerine (1891; 1892). There are two varieties of alexias: central alexias and peripheral alexias (especially agnozic alexia and attentional alexia). In agnozic alexia, the patient cannot read, but can write, understand and speak. It results from a type of cerebral disconnection in which the angular gyrus of the dominant hemisphere is disconnected from its bilateral visual input. The most commonly reported pathology is occlusion of the dominant (left) posterior cerebral artery, which leads to infarction of both the left occipital lobe (causing partial or complete right homonymous hemianpsia) and the splenium of the corpus callosum.

Varieties of alexia from fusiform, posterior inferior temporal and posterior occipital gyrus lesions.

Reading impairments of three alexia patients, two pure alexia and one alexia with agraphia, due to different lesions were examined quantitatively, using Kanji (Japanese morphogram) words, Kana (Japanese phonetic writing) words and Kana nonwords. Kana nonword reading was impaired in all three patients, suggesting that widespread areas in the affected occipital and occipitotemporal cortices were recruited in reading Kana characters (corresponding to European syllables). In addition, the findings in patient 1 (pure alexia for Kanji and Kana from a fusiform and lateral occipital gyri lesion) and patient 2 (pure alexia for Kana from a posterior occipital gyri lesion) suggested that pure alexia could be divided into two types, i.e. ventromedial type in which whole-word reading, together with letter identification, is primarily impaired because of a disconnection of word-form images from early visual analysis, and posterior type in which letter identification is cardinally impaired. Another type of alexia, alexia with agraphia for Kanji from a posterior inferior temporal cortex lesion (patient 3), results from deficient whole-word images of words per se, and thus should be designated "orthographic alexia with agraphia". To account for these impairments, a weighted dual-route hypothesis for reading is suggested.

Aphasia, alexia, and oral reading.

Alexia is an acquired disturbance in reading. Alexias that occur after left hemisphere damage typically result from linguistic deficits and may occur as isolated symptoms or as part of an aphasia syndrome. This article presents an overview of the classification of the alexias, including both the traditional neuroanatomical perspective and the more recent psycholinguistic approach. Then, assessment procedures are reviewed, followed by a summary of treatment approaches for alexia. Finally, two case studies illustrate how oral reading of connected language (sentences and paragraphs rather than single words) has been used as a technique for treating alexia in patients with aphasia.

Alexia and related reading disorders.

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.

Multiple patterns of writing disorders in dementia of the Alzheimer type and their evolution.

This paper reports the results obtained from a writing task given to 23 Italian patients suffering from mild to moderate dementia of the Alzheimer's type (DAT). Spelling performance was tested with a task that taps the sub-word-level (spelling of regular words and nonwords), and the lexical route (spelling of regular and irregular words), in line with contemporary models of writing. Each patient's performance was classified according to the emergence of dissociated patterns of damage between regular words and nonwords and between regular and irregular words. The 23 DAT patients span the whole spectrum of dysgraphic taxonomy; five showed the characteristic pattern of impairment of surface dysgraphia, two showed the characteristics of phonological dysgraphia, while a mixed pattern (i.e. better performance on regular words compared to irregular words and regular nonwords) emerged in seven cases. Three patients presented undifferentiated writing disorders, two were completely agraphic, while four patients showed only minimal or no writing defects. The rate of dissociated impairments in the lexical and the sub-word-level routine is very similar to that observed after acute focal brain damage, which contradicts the hypothesis that degenerative brain damage selectively impairs writing performance along the lexical-semantic route. To test the hypothesis that surface sub-word-level processing abilities are affected only during the evolution of the disease, nine patients were tested longitudinally after an interval of 6-12 months. Once again, the data showed high variability across subjects, and do not seem to support involvement of the sub-word-level spelling routine only at a late stage in the development of the disease.

Stimulus-specific neglect in a deep dyslexic patient.

We report a patient (B.V.) who appears to suffer from two dyslexic disorders. First, B.V. showed a severe impairment in reading aloud nonwords (e.g., reading TREST as TREE), in addition to making several semantic errors when reading aloud words (e.g., reading ILL as SICK) and in picture naming (e.g., responding KNIFE to a picture of a FORK). These results suggest that B.V. suffers from deep dyslexia. Second, B.V. showed an impairment in reading the final letters of both words and nonwords (e.g., reading SHOWN as SHORT and reading PROGE as PROOF). Thus, it appears that B.V. also suffers from neglect dyslexia. We discuss how these two forms of dyslexia could be interacting to account for B.V.'s pattern of errors in reading aloud words and nonwords and in picture naming.

Articulatory processes and phonologic dyslexia.

BACKGROUND/OBJECTIVE: Grapheme-to-phoneme conversion (GPC) allows the pronunciation of nonword letter strings and of real words with which the literate reader has no previous experience. Although cross-modal association between visual (orthographic) and auditory (phonemic-input) representations may contribute to GPC, many cases of deep or phonologic alexia result from injury to anterior perisylvian regions. Thus, GPC may rely upon associations between orthographic and articulatory (phonemic-output) representations. METHOD/RESULTS/CONCLUSION: Detailed analysis of a patient with phonologic alexia suggests that defective knowledge of the position and motion of the articulatory apparatus might contribute to impaired transcoding from letters to sounds.

Kanji-predominant alexia in advanced Alzheimer's disease.

OBJECTIVES: Oral reading is preserved until the late stage of Alzheimer's disease (AD). However, it is unknown whether reading of kanji and kana is differentially impaired in Japanese AD patients. The purpose of this study was to examine alexic pattern in AD as related to two script systems. MATERIAL AND METHODS: In 18 severe AD patients, reading performance was compared among kana characters, monographic kanji words, and kana-transcribed words. Auditory comprehension was also examined. RESULTS: With increased severity of dementia, kanji reading was clearly more impaired than kana reading, which was relatively unaffected. Graphic complexity and frequency of the kanji influenced the performance variously among the patients. Dissociation between kanji reading and comprehension was also noted. CONCLUSION: As a result of multiple cognitive deficits, kanji reading is more impaired than kana reading in AD, but the difference is apparent only in the very late stage. Our findings suggest that kanji can be read correctly without meaning.

Further evidence that reading ability is not preserved in Alzheimer's disease.

BACKGROUND: Pre-morbid intelligence level is routinely assessed in Alzheimer's disease using the National Adult Reading Test (NART). This practice is based on the assumption that pronunciation of irregular words remains unaffected by the disease process. Recent reports have suggested that reading ability may become compromised in moderately demented subjects. METHOD: Sixty-eight probably Alzheimer patients were classified into stages of severity (minimal, mild and moderate) using the Mini-Mental State Examination (MMSE). NART and demographic equations were used to estimate pre-morbid ability. RESULTS: A significant correlation emerged between dementia severity and reading ability, NART v. MMSE scores, r = 0.46, P < 0.01. When the total sample was subdivided into moderate, mild and minimal subgroups, significant between-group differences emerged, despite the groups being well matched for age, sex, and years of full-time education. Pre-morbid IQ, as estimated by demographic regression equations, did not correlate with dementia severity. CONCLUSION: NART performance is compromised in moderate Alzheimer disease, and the measure provides a serious underestimate of pre-morbid IQ in patients with an MMSE of 13 or less.

Two types of phonological alexia.

It is hypothesized, on the basis of a lexical model of reading, that there are two different underlying causes of phonological alexia. It is predicted that these two types of phonological alexia will be accompanied by different sets of symptoms. Published cases of phonological alexia are examined for evidence in support of these predictions. Two distinct groups of phonological alexic patients are observed. These results support the notion of two types of phonological alexia. The failure to find any phonological alexic patients who do not fall into one of these two categories provides evidence against non-lexical reading models.

Perceptual and associative knowledge in category specific impairment of semantic memory: a study of two cases.

We report two head-injured patients whose knowledge of living things was selectively disrupted. Their semantic knowledge was tested with naming and verbal comprehension tasks and a verbal questionnaire. In all of them there was consistent evidence that knowledge of living things was impaired and that of non-living things was relatively preserved. The living things deficit emerged irrespective of whether the question tapped associative or perceptual knowledge or required visual or non visual information. In all tasks the category effect was still significant after the influence on the performance of the following variables was partialled out: word frequency, concept familiarity, prototypicality, name agreement, image agreement and visual complexity. In the verbal questionnaire dissociations were still significant even after adjustment for the difficulty of questions for normals, that had proven greater for living things. Besides diffuse brain damage, both patients presented with a left posterior temporo-parietal lesion.

[A study of alexia in Chinese language].

Twenty-five cases of alexia were examined with Chinese Alexia Test which was devised according to the features of Chinese ideogram. The result of our study showed that alexia in Chinese ideographic language differs from alexia in western phonographic languages. It has its own characteristics and is manifested as following patterns: difficulty in reading aloud, dissociation of appearance and meaning of character, alexia of combinative character, alexia of associative compounds, alexia of abstract word, visual paralexia, surface alexia, deep alexis, phenomenon of word completion (formation of words by addition of another character), substitution with neologisms, perseveration in alexia, character and word alexia, syntactic alexia, and total alexia. Twenty-five cases of alexia were classified according to Benson's classification of alexia as anterior, central, subcortical aphasic and total alexis. One case with proterior alexia was briefly reviewed. The main differential points of various alexia in Chinese language were suggested.

[Neuropsychological differentiation of specific dyslexia in children]. / Neiropsikhologicheskaia differentsiatsiia spetsificheskoi disleksii u detei.

An approach to dyslexia is substantiated in terms of a multilevel organization of written speech (gnostico-praxical and symbolical levels). Two dyslexia forms were differentiated in a neuropsychological investigation of 32 children. First had a selective written speech disorder based upon a visual perception deficit. Second type of dyslexia was caused by a distortion of acoustic symbols of the language which was evident not only in writing and reading disorders but also in impaired notional thinking (language acoustic coding disorder). This approach provides a basis for an adequate pedagogical correction of dyslexia.

Transcortical sensory aphasia: evidence for subtypes.

Impaired auditory comprehension and fluent but semantically empty speech in conjunction with preserved repetition characterize the syndrome of transcortical sensory aphasia (TSA). Repetition, however, may be mediated by at least two distinct processes--a lexical process that may involve the recognition and subsequent activation of discrete stored word representations and a nonlexical process that involves phonologic decoding and immediate phonologic encoding from immediate memory. We investigated the spontaneous speech, reading, and tendency to recognize and spontaneously correct syntactic errors in four patients with TSA: this analysis suggests there are two subtypes of TSA. We contend that in one subtype both the lexical and direct repetition (or speech production) mechanisms are preserved, but in the second subtype the lexical mechanism is disrupted and repetition is mediated by the nonlexical mechanism.