1/38. Subcortical mechanisms in language: lexical-semantic mechanisms and the thalamus.Four previously published cases of dominant thalamic lesion in which the author has participated are reviewed to gain a better understanding of thalamic participation in lexical-semantic functions. Naming deficits in two cases support Nadeau and Crosson's (1997) hypothesis of a selective engagement mechanism involving the frontal lobes, inferior thalamic peduncle, nucleus reticularis, and other thalamic nuclei, possibly the centromedian nucleus. This mechanism selectively engages those cortical areas required to perform a cognitive task, while maintaining other areas in a state of relative disengagement. Deficits in selective engagement disproportionately affect lexical retrieval based on semantic input, as opposed to lexical and sublexical processes, because the former is more dependent upon this attentional system. The concept of selective engagement is also useful in understanding thalamic participation in working memory, as supported by data from one recent functional neuroimaging study. Other processes also may be compromised in more posterior thalamic lesions which damage the pulvinar but not other components of this selective engagement system. A third case with aphasia after a more superior and posterior thalamic lesion also had oral reading errors similar to those in neglect dyslexia. The pattern of deficits suggested a visual processing problem in the early stages of reading. The fourth case had a category-specific naming deficit after posterior thalamic lesion. Taken together, the latter two cases indicate that the nature of language functions in more posterior regions of the dominant thalamus depends upon the cortical connectivity of the thalamic region. Together, findings from the four cases suggest that thalamic nuclei and systems are involved in multiple processes which directly or indirectly support cortical language functions.- - - - - - - - - - ranking = 1keywords = dyslexia, reading (Clic here for more details about this article) |
2/38. Visual implicit memory deficit and developmental surface dyslexia: a case of early occipital damage.This study reports the case of EBON, a fifteen-year-old right-handed female Swedish student, who suffered an early medial/dorsal occipital brain lesion and showed a clearly defined pattern of developmental surface dyslexia. EBON and 17 controls were examined with within and cross-modality (visual and auditory) word stem completion tasks together with tasks requiring free-recall and recognition for visually and auditory presented words. Compared to age-matched controls, EBON was found to show a significant deficit of visual priming following visual presentation, and a deficit approaching significance following auditory presentation. Explicit memory and visual and spatial abilities were not significantly different from controls. Therefore, EBON represents the first childhood case establishing the role of occipital regions in visual priming, as well as illustrating a profile of surface reading difficulty as a developmental consequence of this locus of lesion.- - - - - - - - - - ranking = 3.3897155658853keywords = dyslexia, reading (Clic here for more details about this article) |
3/38. 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.- - - - - - - - - - ranking = 3.6359203270667keywords = dyslexia, reading, alexia (Clic here for more details about this article) |
4/38. Interhemispheric transfer time in a patient with a partial lesion of the corpus callosum.The interhemispheric transfer time (ITT) of basic visuo-motor integration was investigated in a patient who had a lesion of the corpus callosum that spared the splenium and rostrum. overall, 4291 simple reaction times were collected during unimanual responses to tachistoscopically presented lateralized simple visual stimuli at 4 degrees, 6 degrees and 10 degrees. Despite retaining some abilities that typically require the integration of information between hemispheres (e.g. haptic naming, tachistoscopic lateralized consonant reading) the patient performed similarly to completely callosotomized patients in a basic visuo-motor ITT task (overall 25.5 ms) at any eccentricity. These findings suggest that specific callosal channels mediate the basic visuo-motor ITT and these do not include the rostrum and/or the splenium of the corpus callosum.- - - - - - - - - - ranking = 0.17892049267941keywords = reading (Clic here for more details about this article) |
5/38. Naming of musical notes: a selective deficit in one musical clef.We investigated the ability to perform solfeggio, i.e. oral reading of musical notes in MP, a 65 year-old female professional musician, who, following a left temporoparietal ischemia, showed a complex pattern of amusia. The deficit on which we focused was her inability to read orally the bass (F) clef, often substituting it with the violin (G) clef. This problem could not be attributed to a lack of comprehension. The patient could in fact correctly perform on the piano the same sequences she erroneously read aloud; she was also able to correctly judge whether two strings, one in bass clef and the other in violin clef, represented the same sequence of notes. The problem seems to lie in the inability to retrieve note names keeping into account the clef-rule. It is hypothesized that, in the production of note names, this function requires the identification and application of syntactic-like information, in analogy with what is thought to happen in the retrieval of other words.- - - - - - - - - - ranking = 0.17892049267941keywords = reading (Clic here for more details about this article) |
6/38. Impaired short temporal interval discrimination in a dyslexic adult.The ability to discriminate short temporal intervals was examined in a dyslexic adult (E.C.) and six matched controls. Listeners had to decide whether the second interval was shorter or longer than a standard (target) interval. Each interval was defined as the silent duration between two successive brief tones. Eight target intervals were used, ranging from 100 to 1,200 ms in duration. At each target interval, the differential threshold (DL) for duration was assessed, with the use of an adaptive psychophysical procedure. The results show that E.C.'s differential threshold values were much larger than those of controls. Moreover, the slope estimates covering the duration range from 100 to 800 ms indicated that in comparison to controls, E.C.'s differential threshold increased dramatically as the target duration increased. Thus her timing impairment becomes more pronounced with increasing duration. This timing deficit is consistent with other studies that have found temporal processing deficits associated with dyslexia.- - - - - - - - - - ranking = 0.64215901464118keywords = dyslexia (Clic here for more details about this article) |
7/38. 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.- - - - - - - - - - ranking = 3.3578409853588keywords = dyslexia, reading (Clic here for more details about this article) |
8/38. Lexical processes and eye movements in neglect dyslexia.Neglect dyslexia is a disturbance in the allocation of spatial attention over a letter string following unilateral brain damage. patients with this condition may fail to read letters on the contralesional side of an orthographic string. In some of these cases, reading is better with words than with non-words. This word superiority effect has received a variety of explanations that differ, among other things, with regard to the spatial distribution of attention across the letter string during reading. The primary goal of the present study was to explore the interaction between attention and lexical processes by recording eye movements in a patient (F.C.) with severe left neglect dyslexia who was required to read isolated word and non-word stimuli of various length. F.C.'s ocular exploration of orthographic stimuli was highly sensitive to the lexical status of the letter string. We found that: (1) the location to which F.C. directed his initial saccade (obtained approximately 230 ms post-stimulus onset) differed between word and non-word stimuli; (2) the patient spent a greater amount of time fixating the contralesional side of word than non-word strings. Moreover, we also found that F.C. failed to identify the left letters of a string despite having fixated them, thus showing a clear dissociation between eye movement responses and conscious access to orthographic stimuli. Our data suggest the existence of multiple interactions between lexical, attentional and eye movement systems that occur from very initial stages of visual word recognition.- - - - - - - - - - ranking = 4.2107950732059keywords = dyslexia, reading (Clic here for more details about this article) |
9/38. Visuospatial hemi-inattention following cerebellar/brain stem bleeding.Neglect is a unilateral lack of responsiveness to stimuli caused by visuospatial hemi-inattention, a unilateral representation deficit and/or a unilateral hypokinesia. It results most frequently from right-hemisphere brain damage, particularly of the parietal lobe but also of the frontal cortex, the basal ganglia, the thalamus, and recently it has also been described after a cerebellar lesion. We report a patient with right-sided bleeding of the posterior inferior cerebellar artery, who developed a left-sided visual hemi-inattention. She had no visual field defects, yet she had problems detecting left-sided targets in visual extinction. Furthermore, she was impaired in detecting complex motion on the left side and targets in a fixation offset paradigm. Reactions to left-sided targets in covert shifts of attention were slowed in the invalid condition. Her text reading was impaired as she could not always find the initial word of the next line. However, she was aware of her deficit. Her visuoconstructive ability was normal and she gave no indication of tactile or acoustic extinction. As the cerebellar lesion was located in the right hemisphere and the inattention involved the left side of space, we suggest that the damage to the right brain stem led to a transient imbalance of the noradrenergic ascending activation system which may explain her hemi-inattention.- - - - - - - - - - ranking = 0.17892049267941keywords = reading (Clic here for more details about this article) |
10/38. Spatial and motor neglect in children.OBJECTIVE: To determine if unilateral spatial neglect can be found in very young children with acquired brain lesions. methods: A retrospective study was carried out over a 10-year period in a pediatric rehabilitation department specializing in acquired brain lesions. Twelve cases were selected involving children aged 7 months to 14 years. Neglect was assessed by behavior observation for all children and, depending on age, by drawing, copying, reading, writing, and arithmetic tasks. Seven patients underwent the experimental "Teddy Bear" cancellation task, specially adapted to children. RESULTS: All children exhibited spatial and motor neglect in daily activities. In addition, children who were over 2 years of age made lateralized omissions in paper and pencil tasks as well as in the "Teddy Bear" cancellation task. Nine of the 12 children exhibited left spatial and motor neglect, whereas the other three, all of whom were very young (under 4 years), exhibited right spatial neglect. In three cases, cortical lesions were restricted to one lobe, either the parietal, frontal, or temporal. In eight children, lesions extended over more than one lobe, and one child sustained only subcortical lesions. CONCLUSION: Unilateral spatial and motor neglect occurs even in very young children. Right spatial neglect described in very young children may be related to the development of hemispheric specialization.- - - - - - - - - - ranking = 0.17892049267941keywords = reading (Clic here for more details about this article) |
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