1/55. rehabilitation of a case of pure alexia: exploiting residual abilities.We present a case study of a 43-year-old woman with chronic and stable pure alexia. Using a multiple baseline design we report the results of two different interventions to improve reading. First, a restitutive treatment approach using an implicit semantic access strategy was attempted. This approach was designed to exploit privileged access to lexical-semantic representations and met with little success. Treatment was then switched to a substitutive treatment strategy, which involved using the patient's finger to pretend to copy the letters in words and sentences. reading using this motor cross-cuing strategy was 100% accurate and doubled in speed after 4 weeks of intervention. We propose that this patient's inability to benefit from the implicit semantic access treatment approach may be in part related to her inability to suppress the segmental letter identification process of word recognition.- - - - - - - - - - ranking = 1keywords = recognition (Clic here for more details about this article) |
2/55. 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 = 1keywords = recognition (Clic here for more details about this article) |
3/55. brain activation during reading in deep dyslexia: an MEG study.Magnetoencephalographic (MEG) changes in cortical activity were studied in a chronic Finnish-speaking deep dyslexic patient during single-word and sentence reading. It has been hypothesized that in deep dyslexia, written word recognition and its lexical-semantic analysis are subserved by the intact right hemisphere. However, in our patient, as well as in most nonimpaired readers, lexical-semantic processing as measured by sentence-final semantic-incongruency detection was related to the left superior-temporal cortex activation. Activations around this same cortical area could be identified in single-word reading as well. Another factor relevant to deep dyslexic reading, the morphological complexity of the presented words, was also studied. The effect of morphology was observed only during the preparation for oral output. By performing repeated recordings 1 year apart, we were able to document significant variability in both the spontaneous activity and the evoked responses in the lesioned left hemisphere even though at the behavioural level, the patient's performance was stable. The observed variability emphasizes the importance of estimating consistency of brain activity both within and between measurements in brain-damaged individuals.- - - - - - - - - - ranking = 1keywords = recognition (Clic here for more details about this article) |
4/55. 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 = recognition (Clic here for more details about this article) |
5/55. Tactile agnosia and tactile aphasia: symptomatological and anatomical differences.Two patients with tactile naming disorders are reported. Case 1 (right hand tactile agnosia due to bilateral cerebral infarction) differentiated tactile qualities of objects normally, but could neither name nor categorize the objects. Case 2 (bilateral tactile aphasia after operation of an epidural left parietal haematoma) had as severe a tactile naming disturbance as Case 1, but could categorize objects normally, demonstrating that tactile recognition was preserved. Case 1 may be the first case of tactile agnosia clearly differentiated from tactile aphasia. CT scans of Case 1 revealed lesions in the left angular gyrus, and in the right parietal, temporal, and occipital lobes. Case 2 had lesions in the left angular gyrus and of posterior callosal radiations. Our findings suggest that tactile agnosia appears when the somatosensory association cortex is disconnected by a subcortical lesion of the angular gyrus from the semantic memory store located in the inferior temporal lobe, while tactile aphasia represents a tactual-verbal disconnection.- - - - - - - - - - ranking = 8150.0371008979keywords = agnosia, recognition (Clic here for more details about this article) |
6/55. 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 = recognition (Clic here for more details about this article) |
7/55. 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 = 4keywords = recognition (Clic here for more details about this article) |
8/55. Visual object agnosia and pure word alexia: correlation of functional magnetic resonance imaging and lesion localization.We present a case of a 64-year-old, right-handed female with a metastatic breast cancer lesion involving the left posterior inferior temporal lobe causing complete loss of the ability to recognize visually common objects and words. After her symptoms resolved on corticosteroid therapy, functional magnetic resonance imaging (fMRI) mapping demonstrated strong left-hemispheric dominance for word recognition and right-hemispheric dominance for object recognition. The case illustrates the relationships among ventral occipito-temporal cortical activation, lesion localization, and lesion-induced deficits of higher visual function. The relationship between hemispheric dominance determined by fMRI and risk of postoperative deficit depends on the specific visual function of interest.- - - - - - - - - - ranking = 4658.5926290845keywords = agnosia, recognition (Clic here for more details about this article) |
9/55. How to make the word-length effect disappear in letter-by-letter dyslexia: implications for an account of the disorder.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.- - - - - - - - - - ranking = 2keywords = recognition (Clic here for more details about this article) |
10/55. Pure alexia and right hemiachromatopsia in posterior dementia.A 66 year old, right handed woman presented with pure alexia and right hemiachromatopsia (PARH) in the context of a posterior dementia. PARH was accompanied by prosopagnosia, 2-D object agnosia, and environmental agnosia. visual fields were normal to confrontation testing. The pathological anatomy of PARH involves circumscribed damage to the lingual and fusiform gyri and paraventricular white matter of the left occipital cortex, two contiguous cortical regions functionally specialised for processing colour and word form information, respectively.- - - - - - - - - - ranking = 3885.472992777keywords = agnosia, prosopagnosia (Clic here for more details about this article) |
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