1/128. Lexical access via letter naming in a profoundly alexic and anomic patient: a treatment study.We report the results of a letter naming treatment designed to facilitate letter-by-letter reading in an aphasic patient with no reading ability. Patient M.R.'s anomia for written letters reflected two loci of impairment within visual naming: impaired letter activation from print (a deficit commonly seen in pure alexic patients who read letter by letter) and impaired access to phonology via semantics (documented in a severe multimodality anomia). Remarkably, M.R. retained an excellent ability to pronounce orally spelled words, demonstrating that abstract letter identities could be activated normally via spoken letter names, and also that lexical phonological representations were intact when accessed via spoken letter names. M.R.'s training in oral naming of written letters resulted in significant improvement in her oral naming of trained letters. Importantly, as M.R.'s letter naming improved, she became able to employ letter-by-letter reading as a compensatory strategy for oral word reading. M.R.'s success in letter naming and letter-by-letter reading suggests that other patients with a similar pattern of spared and impaired cognitive abilities may benefit from a similar treatment. Moreover, this study highlights the value of testing the pronunciation of orally spelled words in localizing the source of prelexical reading impairment and in predicting the functional outcome of treatment for impaired letter activation in reading.- - - - - - - - - - ranking = 1keywords = visual (Clic here for more details about this article) |
2/128. 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.- - - - - - - - - - ranking = 1keywords = visual (Clic here for more details about this article) |
3/128. 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.- - - - - - - - - - ranking = 8keywords = visual (Clic here for more details about this article) |
4/128. Intact verbal description of letters with diminished awareness of their forms.Visual processing and its conscious awareness can be dissociated. To examine the extent of dissociation between ability to read characters or words and to be consciously aware of their forms, reading ability and conscious awareness for characters were examined using a tachistoscope in an alexic patient. A right handed woman with 14 years of education presented with incomplete right hemianopia, alexia with kanji (ideogram) agraphia, anomia, and amnesia. brain MRI disclosed cerebral infarction limited to the left lower bank of the calcarine fissure, lingual and parahippocampal gyri, and an old infarction in the right medial frontal lobe. Tachistoscopic examination disclosed that she could read characters aloud in the right lower hemifield when she was not clearly aware of their forms and only noted their presence vaguely. Although her performance in reading kanji was better in the left than the right field, she could read kana (phonogram) characters and Arabic numerals equally well in both fields. By contrast, she claimed that she saw only a flash of light in 61% of trials and noticed vague forms of stimuli in 36% of trials. She never recognised a form of a letter in the right lower field precisely. She performed judgment tasks better in the left than right lower hemifield where she had to judge whether two kana characters were the same or different. Although dissociation between performance of visual recognition tasks and conscious awareness of the visual experience was found in patients with blindsight or residual vision, reading (verbal identification) of characters without clear awareness of their forms has not been reported in clinical cases. Diminished awareness of forms in our patient may reflect incomplete input to the extrastriate cortex.- - - - - - - - - - ranking = 2.069128095507keywords = visual, contrast (Clic here for more details about this article) |
5/128. language and calculation within the parietal lobe: a combined cognitive, anatomical and fMRI study.We report the case of a patient (ATH) who suffered from aphasia, deep dyslexia, and acalculia, following a lesion in her left perisylvian area. She showed a severe impairment in all tasks involving numbers in a verbal format, such as reading aloud, writing to dictation, or responding verbally to questions of numerical knowledge. In contrast, her ability to manipulate non-verbal representations of numbers, i.e., Arabic numerals and quantities, was comparatively well preserved, as evidenced for instance in number comparison or number bisection tasks. This dissociated impairment of verbal and non-verbal numerical abilities entailed a differential impairment of the four arithmetic operations. ATH performed much better with subtraction and addition, that can be solved on the basis of quantity manipulation, than with multiplication and division problems, that are commonly solved by retrieving stored verbal sequences. The brain lesion affected the classical language areas, but spared a subset of the left inferior parietal lobule that was active during calculation tasks, as demonstrated with functional MRI. Finally, the relative preservation of subtraction versus multiplication may be related to the fact that subtraction activated the intact right parietal lobe, while multiplication activated predominantly left-sided areas.- - - - - - - - - - ranking = 0.069128095507016keywords = contrast (Clic here for more details about this article) |
6/128. Neuropsychological evidence for case-specific reading: multi-letter units in visual word recognition.We describe a patient (GK) who shows symptoms associated with Balint's syndrome and attentional dyslexia. GK was able to read words, but not nonwords. He also made many misidentification and mislocation errors when reporting letters in words, suggesting that his word-naming ability did not depend upon preserved position-coded, letter identification. We show that GK was able to read lower-case words better than upper-case words, but upper-case abbreviations better than lower-case abbreviations. Spacing the letters in abbreviations disrupted identification, as did mixing the case of letters within words. These data cannot be explained in terms of letter-based reading or preserved holistic word recognition. We propose that GK was sensitive to the visual familiarity of adjacent letter forms.- - - - - - - - - - ranking = 5keywords = visual (Clic here for more details about this article) |
7/128. Alexia with left homonymous hemianopia without agraphia. A case report with autopsy findings.Unusual findings at autopsy prompted this case report of a patient with the syndrome of alexia without agraphia. The expected disconnection of the left angular gyrus from both visual cortices was not found at postmortem examination. Multiple cerebral metastases were identified, but none were present in the presumed pathways connecting the left occipital lobe and the left angular gyrus.- - - - - - - - - - ranking = 1keywords = visual (Clic here for more details about this article) |
8/128. Left hemiparalexia.Three patients with left splenial lesions made paralexic errors restricted to the left end of words. Errors appeared more frequently when a correct response was highly dependent on the initial letter of the stimulus. One patient had full visual fields with hemialexia affecting the left visual field. The other two patients had complete right hemianopia. We attribute left-sided reading errors in the hemianopic patients to a retinotopically restricted disconnection pattern that selectively disrupts transfer of information originating from the peripheral left visual field. Functional resistance of the more numerous transcallosal projections representing visual field adjacent to the vertical meridian may account for such a pattern. The emergence of positional reading errors from retinotopically restricted left hemifield disconnection suggests that callosal information transfer during normal reading may primarily involve elemental sensory rather than lexical/semantic information.- - - - - - - - - - ranking = 4keywords = visual (Clic here for more details about this article) |
9/128. Remediation of alexia without agraphia: a case study.Following a left temporoparietal-occipital haemorrhage and surgery, a 43-year-old, right-handed male exhibited alexia without agraphia. A remediation programme consisted of training in head turning to compensate for a right visual field defect, letter-by-letter reading aloud and covertly, drill with flash-cards to improve word recognition and practice in naming objects to improve dysnomia. The patient's reading improved markedly over a 6-week period and he was able to resume work as a respiratory therapy supervisor. A post-morbid depression resolved concomitantly with the patient's return to work. The training programme and the patient's post-training approach to reading are discussed in terms of hemispheric functioning as well as 'direct path' and 'indirect path' reading. The effectiveness of training is considered in the context of spontaneous recovery.- - - - - - - - - - ranking = 1keywords = visual (Clic here for more details about this article) |
10/128. Visual word recognition in the left and right hemispheres: anatomical and functional correlates of peripheral alexias.According to a simple anatomical and functional model of word reading, letters displayed in one hemifield are first analysed through a cascade of contralateral retinotopic areas, which compute increasingly abstract representations. Eventually, an invariant representation of letter identities is created in the visual word form area (VWFA), reproducibly located within the left occipito-temporal sulcus. The VWFA then projects to structures involved in phonological or lexico-semantic processing. This model yields detailed predictions on the reading impairments that may follow left occipitotemporal lesions. Those predictions were confronted to behavioural, anatomical and functional MRI data gathered in normals and in patients suffering from left posterior cerebral artery infarcts. In normal subjects, alphabetic stimuli activated both the VWFA and the right-hemispheric symmetrical region (R-VWFA) relative to fixation, but only the VWFA showed a preference for alphabetic strings over simple chequerboards. The comparison of normalized brain lesions with reading-induced activations showed that the critical lesion site for the classical syndrome of pure alexia can be tightly localized to the VWFA. reading impairments resulting from deafferentation of an intact VWFA from right- or left-hemispheric input were dissected using the same methods, shedding light on the connectivity of the VWFA. Finally, the putative role of right-hemispheric processing in the letter-by-letter reading strategy was clarified. In a letter-by-letter reader, the R-VWFA assumed some of the functional properties normally specific to the VWFA. These data corroborate our initial model of normal word perception and underline that an alternative right-hemispheric pathway can underlie functional recovery from alexia.- - - - - - - - - - ranking = 1keywords = visual (Clic here for more details about this article) |
| | Next -> |