Archive for July, 2006
The effect of word length on lexical decision in dyslexic and normal reading children.
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The effect of word length on lexical decision in dyslexic and normal reading children.
Brain Lang. 2006 Aug;98(2):140-9
Authors: Martens VE, de Jong PF
In the present study, the effect of word length on lexical decision in dyslexic and normal reading children was investigated. Dyslexics of 10-years old, chronological age controls, and reading age controls read words and pseudowords consisting of 3 to 6 letters in a lexical decision task. Length effects were much stronger in dyslexics and reading age controls than in chronological age controls. These results support the contention that dyslexics continue to rely on a predominantly sub-lexical reading procedure, whereas for normal readers the contribution of a lexical reading procedure increases. The relevance of the findings for current computational models of reading is discussed.
PMID: 16690111 [PubMed - indexed for MEDLINE]
(Source: Brain and Language)
Original post by Brain and Language
No commentsNeuroanatomical and behavioral asymmetry in an adult compensated dyslexic.
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Neuroanatomical and behavioral asymmetry in an adult compensated dyslexic.
Brain Lang. 2006 Aug;98(2):169-81
Authors: Chiarello C, Lombardino LJ, Kacinik NA, Otto R, Leonard CM
Individual differences in cortical anatomy are readily observable, but their functional significance for behaviors such as reading is not well understood. Here, we report a case of an apparent compensated dyslexic who had attained high achievement in visuospatial mathematics. Data from a detailed background interview, psychometric testing, divided visual field tasks measuring basic word recognition (word naming, nonword naming, and lexical decision), and more controlled word retrieval (verb, category, and rhyme generation), and measurements of his atypical brain structure are described. The findings suggested that enhanced “top-down” processing could provide the means to compensate for deficient “bottom-up” word decoding skills in this case. Relative to controls, this individual also evidenced unusually large asymmetries on several divided visual field lexical tasks, an extreme leftward asymmetry of the planum temporale, and a rare form of Sylvian fissure morphology (Steinmetz type 4, [Steinmetz, H., Ebeling, U., Huang, Y., & Kahn, T. (1990). Sulcus topography of the parietal opercular region: An anatomic and MR study. Brain and Language, 38, 515-533.]). We suggest that certain forms of brain organization may be associated with successful behavioral compensation for dyslexia, and that anatomical variations in the right hemisphere may be important contributors to individual differences in reading acquisition and achievement.
PMID: 16737735 [PubMed - indexed for MEDLINE]
(Source: Brain and Language)
Original post by Brain and Language
No commentsSpeech perception in preschoolers at family risk for dyslexia: relations with low-level auditory processing and phonological ability.
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Speech perception in preschoolers at family risk for dyslexia: Relations with low-level auditory processing and phonological ability.
Brain Lang. 2006 Aug 1;
Authors: Boets B, Ghesquière P, van Wieringen A, Wouters J
We tested categorical perception and speech-in-noise perception in a group of five-year-old preschool children genetically at risk for dyslexia, compared to a group of well-matched control children and a group of adults. Both groups of children differed significantly from the adults on all speech measures. Comparing both child groups, the risk group presented a slight but significant deficit in speech-in-noise perception, particularly in the most difficult listening condition. For categorical perception a marginally significant deficit was observed on the discrimination task but not on the identification task. Speech parameters were significantly related to phonological awareness and low-level auditory measures. Results are discussed within the framework of a causal model where low-level auditory problems are hypothesized to result in subtle speech perception problems that might interfere with the development of phonology and reading and spelling ability.
PMID: 16887179 [PubMed - as supplied by publisher]
(Source: Brain and Language)
Original post by Brain and Language
No commentsDelayed detection of tonal targets in background noise in dyslexia.
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Delayed detection of tonal targets in background noise in dyslexia.
Brain Lang. 2006 Aug 1;
Authors: Chait M, Eden G, Poeppel D, Simon JZ, Hill DF, Flowers DL
Individuals with developmental dyslexia are often impaired in their ability to process certain linguistic and even basic non-linguistic auditory signals. Recent investigations report conflicting findings regarding impaired low-level binaural detection mechanisms associated with dyslexia. Binaural impairment has been hypothesized to stem from a general low-level processing disorder for temporally fine sensory stimuli. Here we use a new behavioral paradigm to address this issue. We compared the response times of dyslexic listeners and their matched controls in a tone-in-noise detection task. The tonal signals were either Huggins Pitch (HP), a stimulus requiring binaural processing to elicit a pitch percept, or a pure tone-perceptually similar but physically very different signals. The results showed no difference between the two groups specific to the processing of HP and thus no evidence for a binaural impairment in dyslexia. However, dyslexic subjects exhibited a general difficulty in extracting tonal objects from background noise, manifested by a globally delayed detection speed.
PMID: 16887180 [PubMed - as supplied by publisher]
(Source: Brain and Language)
Original post by Brain and Language
No commentsParietal function in good and poor readers
Background:
While there are many psychophysical reports of impaired magnocellular pathway function in developmental dyslexia (DD), few have investigated parietal function, the major projection of this pathway, in good and poor readers closely matched for nonverbal intelligence. In view of new feedforward-feedback theories of visual processing, impaired magnocellular function raises the question of whether all visually-driven functions or only those associated with parietal cortex functions are equally impaired and if so, whether parietal performance is more closely related to general ability levels than reading ability.
Methods:
Reading accuracy and performance on psychophysical tasks purported to selectively activate parietal cortex such as motion sensitivity, attentional tracking, and spatial localization was compared in 17 children with DD, 16 younger reading-age matched (RA) control children, and 46 good readers of similar chronological-age (CA) divided into CA-HighIQ and a CA-LowIQ matched to DD group nonverbal IQ.
Results:
In the age-matched groups no significant differences were found between DD and CA controls on any of the tasks relating to parietal function, although performance of the DD group and their nonverbal IQ scores was always lower. As expected, CA and RA group comparisons indicated purported parietal functioning improves with age. No difference in performance was seen on any of the parietally driven tasks between the DD and age-nonverbal IQ matched groups, whereas performance differentiated the DD group from the age-matched, higher nonverbal IQ group on several such tasks. An unexpected statistical difference in performance between lower reading age (DD and RA children) and all higher reading age (CA) children was seen on a test of chromatic sensitivity, whereas when high and low nonverbal IQ normal readers were compared performance was not different
Conclusions:
The results indicate that performance on purported parietal functions improves with age and may be more associated with nonverbal mentation than reading accuracy. Performance on a cognitively demanding task, traditionally considered to rely on ventral stream functions, was more related to reading accuracy. (Source: BioMed Central)
Original post by BioMed Central
No commentsLearning Disabilities: NIH Turns To FSU For Top Research
Florida State University has been awarded a $6-million grant from the federal government over five years to fund research efforts aimed at more effectively understanding, predicting and preventing the development of learning disabilities such as dyslexia in children, it was announced today.The grant will fund the creation of a National Institutes of Health (NIH) Multidisciplinary Learning Disabilities Center at FSU. [click link for full article]
Original post by Allergy News From Medical News Today
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