ABSTRACT
Although the dominant view posits that developmental dyslexia arises from a deficit in phonological processing and memory, efficient phonological decoding requires precise visual selection of graphemes. Therefore, visual engagement and disengagement of non-spatial attention were studied in 13 dyslexic children and 13 chronological age and intelligence quotient (IQ) matched normally reading children by measuring "attentional masking" (AM) and "attentional blink" (AB) effects. AM refers to an impaired identification of the first (T1) of two rapidly sequential targets (i.e., attentional engagement). In contrast, AB refers to an impaired identification of the second target in the sequence (T2; i.e., attentional disengagement). The results revealed a specific temporal deficit of AM as well as of AB in dyslexic children. Our results showed that the abnormality in AM and AB is rather widespread, since 77% and 54% of dyslexic children deviated at least 1 standard deviation (SD) from the mean of the controls, respectively, for the two deficits. We further showed that individual differences in non-spatial attention were specifically related to nonword reading ability. These results suggest that non-spatial attention deficits (possibly related to a parietal cortex dysfunction) may selectively impair the reading development via sub-lexical mechanisms.
Subject(s)
Attention/physiology , Dyslexia/physiopathology , Form Perception/physiology , Psychomotor Performance/physiology , Space Perception/physiology , Adolescent , Child , Dyslexia/psychology , Female , Humans , Intelligence/physiology , Male , Pattern Recognition, Visual/physiology , Photic Stimulation/methods , Reaction Time/physiology , Reading , Verbal Learning/physiologyABSTRACT
Two groups of children with developmental dyslexia were treated over a period of four months. Fourteen children received visual hemisphere-specific stimulation (VHSS) and 11 children were treated with a customary, reading-focused training programme (RT). Reading performance was investigated before and after treatment, as were spelling abilities, phonemic awareness and verbal memory. Improvement in reading accuracy was significantly greater in the VHSS group than in the RT group. Significant improvements were also observed for memory and phonemic skills. The results were compared to existing data on spontaneous reading development. The better results after single-hemisphere stimulation (VHSS) are discussed in terms of the specific characteristics of the treatment, and of the possible contributions of visual-spatial attention, memory functions and phonemic awareness.
Subject(s)
Dyslexia/rehabilitation , Functional Laterality/physiology , Photic Stimulation/methods , Reading , Remedial Teaching/methods , Adolescent , Analysis of Variance , Attention/physiology , Child , Female , Humans , Male , Memory/physiology , Phonetics , Time Factors , Verbal Learning/physiologyABSTRACT
Focused visuo-spatial attention was studied in 10 developmental dyslexic children with impaired nonword reading, 10 dyslexic children with intact nonword reading, and 12 normally reading children. Reaction times to lateralized visual stimuli in a cued detection task showed that attentional facilitation of the target at the cued location was symmetrical in the three groups. However, dyslexics with impaired nonword reading selectively showed a lack of attentional inhibition for targets at the uncued location in the right visual field. This result was replicated in a second group of 13 dyslexics with impaired nonword reading. Individual differences in the ability of right attentional inhibition across the entire sample of dyslexics accounted for 17% of unique variance in nonword reading accuracy after controlling for individual differences in age, IQ, and phonological skills. A possible explanation based on the role of spatial attention mechanisms in the graphemic parsing process is discussed. Our results suggest that focused visuo-spatial attention may be crucial for nonword decoding.
ABSTRACT
A cue size procedure was used to evaluate the time course of visuo-spatial attention in dyslexic and normally reading children. When a stimulus target is presented inside a large cue vs a small cue the identification time is slower. In the present study two cue-target delays (100 and 500 ms) were used. Results showed a slower time course of attentional focusing in dyslexics vs normal readers. Indeed, dyslexics exhibited no cue size effect at a shorter cue-target delay (100 ms), while it was present at a longer cue-target delay (500 ms). In contrast, a cue size effect was found at both cue-target delays in normally reading children. These results further support the hypothesis of sluggish automatic focusing of visual attention in dyslexics. This impairment could be a consequence of a general magnocellular deficit demonstrated previously in dyslexics.
Subject(s)
Attention , Dyslexia/physiopathology , Child , Cues , Eye Movements/physiology , Female , Humans , Male , Parietal Lobe/physiopathology , Reaction Time , Space Perception/physiology , Visual Perception/physiologyABSTRACT
Several studies have provided evidence for a phonological deficit in developmental dyslexia. However, recent studies provide evidence for a multimodal temporal processing deficit in dyslexia. In fact, dyslexics show both auditory and visual abnormalities, which could result from a more general problem in the perceptual selection of stimuli. Here we report the results of a behavioral study showing that children with dyslexia have both auditory and visual deficits in the automatic orienting of spatial attention. These findings suggest that a deficit of selective spatial attention may distort the development of phonological and orthographic representations that is essential for learning to read.
Subject(s)
Attention Deficit Disorder with Hyperactivity/psychology , Attention/physiology , Auditory Perception/physiology , Dyslexia/psychology , Visual Perception/physiology , Acoustic Stimulation , Child , Cues , Female , Humans , Male , Photic Stimulation , Reaction Time/physiology , Reading , Wechsler ScalesABSTRACT
Shifting of visual attention induced by peripheral cues was studied in 24 children with specific reading disorder (SRD) or dyslexia and was compared with that of 19 normal readers by means of a covert orienting paradigm. This paradigm presents participants with valid, neutral and invalid spatial cues preceding the presentation of a target stimulus. As compared to normal readers, in SRD children the inhibition effect (i.e. the difference between neutral and invalid cues) was absent. The 24 SRD children were divided into two groups matched for age, IQ and reading ability to study the efficacy of two different rehabilitation procedures. We assessed the effects on reading accuracy and speed over a 4-month treatment with visual hemisphere specific stimulation (VHSS; J. Learn Disabil. 25 (1992) 102) vs. traditional speech training. The VHSS program trains participants to perform rapid endogenous attentional orienting by presenting briefly flashed words in the peripheral visual field. We found that children treated with VHSS showed significant changes in their attentional inhibition process, as indicated by increased costs for 'reorienting' the attentional focus. As this treatment program also proved to be highly efficient in improving the children's reading abilities, the possible causal relationship between reading and inhibition mechanisms of visuospatial attention was discussed.
