Identifying subtypes of reading disability in the Spanish language

This study was designed to examine the dyslexic subtypes in a transparent orthography (i.e., Spanish language). The subtyping procedure used comparison with chronological-age-matched and reading-level controls on reaction times (RTs) to high frequency words and to pseudowords. Using regression-based procedures, the authors identified 20 phonological and 48 surface dyslexics from a sample of 89 dyslexic third-grade children by comparing them to chronological-age-matched controls on RTs to high frequency and pseudoword reading. However, when the dyslexic subtypes were defined by reference to reading-level controls, the same 20 phonological dyslexics were defined, but only 19 surface dyslexics were identified. Nevertheless, the results of the phonological awareness tasks and error analysis do not validate the division of the dyslexic sample into these subgroups.     

Working memory, inhibitory control, and reading disability

The relationships among working memory, inhibitory control, and reading skills were studied in 966 individuals, 6—49 years old. In addition to a standardized measure of word recognition, they received a working memory (listening span) task in the standard, blocked format (three sets containing two-, three-, or four-item trials) or in a mixed format (three sets each containing two-, three-, and four-item trials) to determine whether scores derived from the standard format are influenced by proactive interference. Intrusion errors were investigated in order to determine whether deficits in working memory were associated with the access, deletion, or restraint functions of inhibitory control. The results indicated that deficits in working memory were characteristic of individuals with reading disabilities at all ages. These deficits may be associated with the access and restraint functions of inhibition. Working memory skills increased until the age of 19. The blocked format showed a gradual decline in adulthood whereas the mixed format did not. The different patterns suggest that the decline in working memory skills associated with aging may result from growing inefficiencies in inhibitory control, and not diminished capacity.     

Home literacy experiences and socio-cultural characteristics associated with the subtypes of reading disability

This study was designed to analyse the home literacy experiences and socio-cultural characteristics associated with the subtypes of reading disability. For this purpose, we used a reading level match design and we selected four samples of families as a function of their children's reading profile: a group of parents (15 fathers and 16 mothers) whose children had a profile of surface dyslexia (DSP); a second group of parents (6 fathers and 6 mothers) whose children had a profile of phonological dyslexia (DFP); a third group of parents (38 fathers and 41 mothers) whose children were matched in age with the children who had learning disabilities (ECP); and a fourth group of parents (33 fathers and 35 mothers) whose children were matched in reading age with children who had learning disabilities (NLP). Both dyslexic subtypes showed a deficit in phonological awareness, but children with surface dyslexia also showed a deficit in orthographical processing assessed by homophone comprehension task. This deficit was related to home literacy experiences because the group of parents whose children had surface dyslexia, in comparison to parents of children matched in reading age, promoted fewer home literacy experiences.     

Separate verbal memory and naming deficits in attention deficit disorder and reading disability

In this study, verbal memory and naming abilities were investigated in reading disabled (RD) and control children who were characterized according to the presence or absence of attention deficit disorder (ADD). Results indicate that deficits in learning and memory for recently acquired information occur as a function of ADD rather than RD while deficits in naming are specific to RD rather than ADD. We conclude that ADD is a major source of additional and separate cognitive morbidity in RD children.     

Immediate memory spans in dementia

Spatial span (Corsi's block-tapping test) and verbal spans for digits (Wechsler Digits Forward Test) and for words were measured in 30 normal subjects and in 51 demented patients, divided into two groups (mildly demented and severely demented) according to selective clinical and neuropsychological criteria. Statistical analysis showed significant differences among the three groups for spatial span. By contrast, controls' and mildly demented patients' performances on both verbal spans were not significantly different. These findings are discussed in the light of theory about working memory.     

Immediate recognition memory for wine

We describe a preliminary investigation concerning the short-term recognition memory function for gustatory stimuli (wines). In Experiment 1A, 24 non-expert wine drinkers completed a yes/no recognition task for 3-wine sequences. For the raw recognition scores, the serial position function comprised both primacy and recency. Recency did not, however, achieve significance for the d′ scores. In Experiment 1B, 24 participants completed the same yes/no recognition task for 3-visual matrix sequences. In contrast to Experiment 1A, the serial position function comprised recency and an absence of primacy. We argue that the presence of primacy for the wine sequences cannot be interpreted via a verbal labelling strategy, nor can it be interpreted via proactive interference from the first wine in the list on subsequent list items. The result suggests qualitative differences in the memory processing for gustatory and non-verbal visual stimuli.     

Immediate memory and simultaneous stimuli

When two sets of digits are presented simultaneously one to one ear and one to the other, the subject may be asked to write them down from immediate memory beginning with those on an ear chosen by the experimenter. He can do this, but any mistakes are usually amongst those on the ear prescribed for later response. If the subject does not know the order of recall until after stimulation, he either shows low efficiency with the same serial order effect, or else normal efficiency with an altered serial order effect.

When the order of recall is known in advance, efficiency is also reduced by altering the time of presentation of the last items to be recalled; and also by inserting irrelevant items. All these facts are consistent with a particular theory of immediate memory.     

Phonemic analysis and severe reading disability in children

Forty-five first-grade children of average intellectual ability were studied, consisting of one group of average readers, one group with mild reading difficulty, and one group with severe reading disability. A striking deficit in phonemic analysis was observed in children with severe reading disability. These children were unable to segment spoken syllables into individual speech sounds, while children with only mild reading difficulty or none were quite proficient at this skill. In fact, using phonemic analysis scores, it was possible to distinguish the severe reading disability group from the others with perfect accuracy.This research was supported in part by U.S. Public Health Service, Maternal and Child Health Project 916, and by Grants HD-03110 and ES-01104 from the National Institutes of Health.     

Immediate memory and simultaneous visual stimulation

Ten right-handed, right eye-dominant aircrew trainees recalled digits and colours projected simultaneously one to each eye, under five binocular viewing conditions that precluded overlap in visual fields.

Results of this experiment favour the view that Broadbent's theory of immediate memory is a special case which, though not typical, is applicable to vision. Relevance of present findings for the problem of cerebral dominance is also discussed.     

Specific reading disability: a multiplanar view

In the past three decades a revolution has altered the way society approaches people with disabilities. Social changes resulted in a significant increase in fundamental and applied research that seeks to improve the lives of people with disabilities by facilitating better understanding of the mechanisms, manifestations, prevention, and treatment of functional impairment. Specific Reading Disability (SRD) has benefited from this revolution. This review focuses on the evolution of SRD, new information in its neurobiology and management, and the challenges that remain. Evidence from a wide spectrum of research provides strong support for the role of phonology in Specific Reading Disability. Despite the mounting evidence, the case is far from completely established. Adults with compensated SRD read but still demonstrate disordered phonology (Felton et al. [1990] Brain Language 39:485-497). Whether poor phonology is causal or a covariant remains to be demonstrated. Of children with poor phonology, it is not known how many are poor readers. While phonology is associated with SRD, other studies have questioned the uniqueness of SRD. Challenges have been made to the method of classification, the uniqueness of phonological dysfunction as a mechanism in SRD and the response to treatment. In the final analysis all poor readers may have a common core of dysphonology, independent of whether their reading is discrepant from their IQ.     

Spatial-frequency-dependent visible persistence and specific reading disability

Visible persistence duration for sine-wave gratings was measured in 9-year-old normal and specific-reading-disabled children. Experiment 1 investigated the influence of stimulus duration on visible persistence. The results demonstrated a Reading Group X Spatial Frequency interaction with disabled readers showing a smaller increase in persistence duration with increasing spatial frequency than controls. This interaction was greatest with stimulus durations longer than 80 msec. In Experiments 2a and 2b persistence was measured across a range of contrasts from .1 to .5. The stimulus durations employed were 100 msec in Experiment 2a and 300 msec in Experiment 2b. In both experiments, increasing contrast decreased persistence duration at 2 and 12 cycles per degree (c/deg) for the control group. In the specific-reading-disabled group, however, contrast had little effect on the persistence of 2-c/deg gratings in either experiment. In Experiment 2a the persistence of the 12-c/deg grating decreased with increasing contrast for both groups. In Experiment 2b contrast had significantly less effect on persistence duration in the specific-reading-disabled group, however, contrast had little effect on the persistence of 2-c/deg ratings in either experiment. In Experiment 2b contrast had significantly less effect on persistence duration in the specific-reading-disabled group than in the control group at 12 c/deg. Consequently, contrast had less effect on persistence in specific-reading-disabled children than in normal readers, especially at durations longer than the "critical duration" for each spatial frequency. Experiment 3 extended this finding to gratings with spatial frequencies of 4 and 8 c/deg. These results indicate a difference between normal and specific-reading-disabled children in cortical visible persistence. Two scores of visual processing were derived from the above experiments. On these scores the reading-disabled children were divided into Visual Disabled Readers (approximately 70%--eight subjects) and Nonvisual Disabled Readers (approximately 30%--four subjects). The percentages of disabled readers in each category remained constant when the sample size was increased to 61 normal and disabled readers.     

Functional neuroimaging studies of reading and reading disability (developmental dyslexia)

Converging evidence from a number of neuroimaging studies, including our own, suggest that fluent word identification in reading is related to the functional integrity of two consolidated left hemisphere (LH) posterior systems: a dorsal (temporo-parietal) circuit and a ventral (occipito-temporal) circuit. This posterior system is functionally disrupted in developmental dyslexia. Reading disabled readers, relative to nonimpaired readers, demonstrate heightened reliance on both inferior frontal and right hemisphere posterior regions, presumably in compensation for the LH posterior difficulties. We propose a neurobiological account suggesting that for normally developing readers the dorsal circuit predominates at first, and is associated with analytic processing necessary for learning to integrate orthographic features with phonological and lexical-semantic features of printed words. The ventral circuit constitutes a fast, late-developing, word identification system which underlies fluent word recognition in skilled readers.     

Working memory in children with reading disabilities

This study investigated associations between working memory (measured by complex memory tasks) and both reading and mathematics abilities, as well as the possible mediating factors of fluid intelligence, verbal abilities, short-term memory (STM), and phonological awareness, in a sample of 46 6- to 11-year-olds with reading disabilities. As a whole, the sample was characterized by deficits in complex memory and visuospatial STM and by low IQ scores; language, phonological STM, and phonological awareness abilities fell in the low average range. Severity of reading difficulties within the sample was significantly associated with complex memory, language, and phonological awareness abilities, whereas poor mathematics abilities were linked with complex memory, phonological STM, and phonological awareness scores. These findings suggest that working memory skills indexed by complex memory tasks represent an important constraint on the acquisition of skill and knowledge in reading and mathematics. Possible mechanisms for the contribution of working memory to learning, and the implications for educational practice, are considered.     

Two-part stimulus integration and specific reading disability.

29 dyslexics and 29 control children were presented with two halves of a black cross, one-half being presented at varying interstimulus intervals after the other half. Both dichoptic and binocular presentations were used and separation thresholds were at greater interstimulus intervals for the dichoptic condition. Dyslexics had thresholds at greater intervals than controls. These differences were significant and there was no significant interaction of group by dichoptic condition. The relative magnitudes of difference between dyslexics and controls were as previously reported by Stanley and Hall (1973) and support the notion that dyslexics have longer visual persistence than controls.     

Learning disability subtypes: classification of high functioning hyperlexia

This study examined 30 children with hyperlexic reading patterns and average intelligence to determine if established learning disability subtypes could be applied to these children with hyperlexia. Two groups emerged. One type showed language learning disorder patterns with good visual memory. This group also showed a high percentage of phonetic word errors. A second hyperlexic group showed signs of nonverbal learning disorder with visual spatial deficits and impaired visual memory. This latter subgroup showed few phonetic errors with more sight word errors. These findings suggest subtypes of high functioning hyperlexia, one showing language deficits characteristic of dysphasia and one showing patterns similar to visual spatial dyslexia.