Attention In Dyslexia Research Articles

Letter Position Dyslexia

Many word-reading models assume that the early stages of reading involve a separate process of letter position encoding. However, neuropsychological evidence for the existence and selectivity of this function has been rather indirect, coming mainly from position preservation in migrations between words in attentional dyslexia, and from nonselective reading deficits. No pure demonstration of selective impairment of letter position function has yet been made. In this paper two Hebrew-speaking acquired dyslexic patients with occipito-parietal lesions are presented who suffer from a highly selective deficit to letter position encoding. As a result of this deficit, they predominantly make errors of letter migration within words (such as reading “broad” for “board”) in a wide variety of tasks: oral reading, lexical decision, same-different decision, and letter location. The deficit is specific to orthographic material, and is manifested mainly in medial letter positions. The implications of the findings to models of reading and attention are discussed.

A peripheral reading deficit under conditions of diffuse visual attention

We report a single case study of a patient, FL, who has a peripheral dyslexia with symptoms resembling attentional dyslexia. FL demonstrated impaired identification of letters within strings, and better identification of words than their constituent letters. We found that FL was impaired at both letter counting and same-case letter matching with letter strings, and his matching and naming performance were strongly affected by letter spacing. The effects of these visual variables on performance suggest an early locus to FL's deficit. We propose that letter identification was disrupted by abnormal lateral masking and poor location coding within words. These peripheral processing deficits were reduced when the task required focused attention on the central letter location. Nevertheless, even with impaired letter coding, word representations could be accessed to some degree, via supra-letter units. We discuss the implications of the data for understanding normal reading.

A peripheral reading deficit under conditions of diffuse visual attention

We report a single case study of a patient, FL, who has a peripheral dyslexia with symptoms resembling attentional dyslexia. FL demonstrated impaired identification of letters within strings, and better identification of words than their constituent letters. We found that FL was impaired at both letter counting and same-case letter matching with letter strings, and his matching and naming performance were strongly affected by letter spacing. The effects of these visual variables on performance suggest an early locus to FL's deficit. We propose that letter identification was disrupted by abnormal lateral masking and poor location coding within words. These peripheral processing deficits were reduced when the task required focused attention on the central letter location. Nevertheless, even with impaired letter coding, word representations could be accessed to some degree, via supra-letter units. We discuss the implications of the data for understanding normal reading.

Orienting of visual attention in dyslexia: evidence for asymmetric hemispheric control of attention

The control of attentional orienting was studied in children with specific reading disorder (SRD) or dyslexia, and it was compared with that of normal readers. We used the covert orienting paradigm to measure subjects' reaction times for target detection both in valid and invalid cue conditions, either in the left or in the right visual fields. In experiment 1, we investigated exogenous orienting. The cue consisted of a peripheral abrupt onset and the cue-target delay was 350 ms. As compared with normal readers, in dyslexics the cue effect was absent in the right visual field, whereas in the left visual field a greater cue effect was observed. No visual field asymmetry was found in normal readers. In experiment 2, we investigated endogenous orienting. The cue was shown centrally and the cue-target delay was 750 ms. In dyslexics and normal readers, orienting of attention was present in both visual fields. However, in the invalid condition, dyslexic children showed significantly slower reaction times in the left visual field than in the right visual field. These results were interpreted as being due to an asymmetric control of visual spatial attention, possibly related with a posterior attention mechanism deficit in the right parietal cortex and/or an interhemispheric dysfunction and/or an impairment of cerebellar functions.

Acquired dyslexia.

Disorders of reading are frequently encountered in patients with acquired cerebral lesions. Investigations in the past few decades have improved our understanding of these disorders. In this article we review the peripheral dyslexias, including neglect dyslexia, attentional dyslexia, and pure alexia (or alexia without agraphia), as well as the "central" dyslexias, including deep, surface, and phonological dyslexia. Current accounts of acquired dyslexia are also discussed. Finally, we briefly describe the reading tasks that serve to differentiate the different reading disorders.

"Attentional Dyslexia" in Alzheimer's Disease: A Case Study

We report a case study of a patient, NY, who developed features of an attentional dyslexia as one manifestation of a variant of Alzheimer's disease in which parieto-occipital areas are most affected. Although able to read single w ords w ithout diffi culty, N Y w as unable to read text. W hen reading two-word displays, he showed an apparent tendency for letters from one word to intrude into the other. Investigation of this phenomenon demonstrated that these errors were due to letter migration as opposed to non-contextual substitution and that the incidence of m igrations decreased when the two words appeared in different case letters. This reduction in interference by physical dissimilarity among the display elements differentiates NY from the two cases described in the original account of attentional dyslexia (Shallice & Warrington, 1977). Analyses of NY's error patterns pointed to the loss of location information as a significant factor in the generation of his migration errors.

Attentional processes and dyslexia

Abstract This review of attentional processes related to dyslexia examines the nature of the “attention” needed to acquire reading skills and proposes a definition of attention that combines elements of neurobiology and neuropsychology. Evidence for a relationship between reading problems and deficits in auditory and/or visual processing circuitry, which could be labelled “attentional deficits” is then outlined, and the final section reports research on possible underlying causes of the deficits from the fields of visual perceptual processing, neurophysiology, and neuroanatomy, and advances in the field of nonlinear dynamical theory, which may contribute eventually to our understanding of the temporal dynamics of neural systems in which “attention” is currently thought to play a part.

Attentional dyslexia: The effect of co-occurring deficits

Abstract The case study of PR, a patient with acquired dyslexia without dysgraphia, is reported. PR was found to have a deficit in accessing phonology from semantics and a mild deficit in attending selectively to the components making up visual displays. Coupled together, these two deficits severely disrupted her ability to name the components of visual arrays although she could name each component in isolation (the symptom of patients classified as attentional dyslexics). We discuss the possible importance of the co-occurrence of two or more deficits in producing some neuropsychological syndromes.

Attentional dyslexia: A single case study

A single case study of an attentional dyslexic is reported. The patient B.A.L. was able to read single letters and single words presented in isolation without difficulty. However, his reading of prose was very disrupted and his ability to read rows of letters and words was significantly impaired. A “flanking” procedure, in which there was a single target item, flanked by other stimuli, was used in a series of experiments to analyse his dyslexic impairment. First it was established that his attentional deficit was specific to reading in so far as the patient did not have comparable difficulties with pictorial material. His performance in the flanking experiments was consistently impaired; and furthermore was unaffected by speed of presentation, the number of flanking stimuli, and the spatial arrangement of the flanking stimuli. The important exception was when the flanking stimuli were of a different category. There was no decrement in performance when target letters were flanked by words or when words were flanked by letters. This study both corroborates and extends the original account of attentional dyslexia (S hallice and W arrington, Neuropsychologia 15, 31–41, 1977) in terms of a damaged “filter” mechanism controlling the transition from a parallel to a serial stage of reading processing. The categorical effects reported here indicate that such a filter must be post lexical and suggest further that there are multiple filters in the reading system.

Selective attentional dyslexia

Abstract A case study is presented of a university professor (SJ) who was classified as a developmental dyslexic when he was a teenager. His reading comprehension was found to be markedly inferior to his listening comprehension; in addition, his reading rate was quite slow. Standardised tests were administered to SJ to provide estimates of his reading ability (and overall intelligence) and a test battery was administered to examine his word retrieval and word recognition skills. While these tests revealed that SJ has some type of word retrieval problem, subsequent testing revealed that a major contributor to his reading problem was a selective attentional deficit in which letters from words in parafoveal vision interfere with his processing of the currently fixated word. When parafoveal vision was restricted, by using the McConkie and Rayner (1975) moving window paradigm in which letters outside of a small, centrally fixated window region were replaced with Xs, SJ's reading performance was actually better than when the entire line of text was present. Implications of these findings for developmental dyslexia were discussed.