Short-term memory performance in the absence of phonological coding

These experiments examined the short-term memory performance of an aphasic patient with posterior damage who shows a selective deficit in phonological coding. In recognition memory tests, the patient relied on both visual and semantic coding, and often showed an essentially normal level of accuracy. However, for memory sets consisting of four function words, his performance was quite impaired. Also, his retention of order information was far below that of normal controls. The implications of these deficits in short-term memory for language comprehension and production are discussed.     

Cross language learning disabilities and verbal versus spatial memory

The research reported in this talk involves comparisons of verbal and spatial memory tasks across groups of children (and adults) with different types of learning difficulties. The research focuses on children with literacy acquisition problems and investigates whether such problems are related to specific areas of deficit. In the first piece of research, children with dyslexia (literacy learning problems) and dyspraxia (motor deficits) were contrasted on measures of memory (for example, tasks that required the retention of sequences of verbal material or spatial movements) and additional measures of literacy (reading and spelling), phonological (awareness of sounds within words) and motor (fine and gross motor tasks) functioning. The data were consistent with a dissociation between tasks/groups such that dyslexics showed weak phonological processing but intact visuo-spatial processing, whereas children with dyspraxia showed weaknesses on task involving visuo-spatial information, but average levels of performance on tasks that required phonological processing. Similar results were identified amongst adult groups, consistent with a deviant level of functioning rather than a developmental delay. A second line of research contrasted children with or without literacy problems across language backgrounds (English, Arabic, Chinese and bilingual children). Consistent with the dyslexia data, children with poor English literacy skills showed weaknesses in verbal/phonological memory tasks but not in visuo-spatial memory. However, for Chinese-language children, visuo-spatial memory differed between good and poor literacy learners, but there was little evidence for verbal memory differences. In contrast, the Arabic and bilingual children showed differences in both verbal and visuo-spatial areas, although the evidence was consistent with enhanced visual/spatial skills amongst the good literacy groups, rather than poor literacy children showing weaknesses in those tasks. These data suggest that the influence of memory skills on learning may vary with the language of instruction. A final line of enquiry considers whether teaching strategies to children with learning difficulties may overcome some of the identified memory deficits and lead to better levels of learning. English language children with learning difficulties were taught visual and verbal strategies to support retention of materials in short-term memory tasks. In the majority of cases, learning was improved when it focused on visuo-spatial strategies but not when verbal strategies were used. These data support the relationship between learning difficulties and different aspects of short-term memory that may lead to poor levels of learning. It also presents evidence that memory (particularly those related to visuo-spatial) processes are influenced by the context within which learning is taking place, both in terms of the language of instruction and the strategies used to support learning. For some children with educational difficulties based around language-related deficits, visuo-spatial strategies may support acquisition.     

Developmental dyslexics do not fit in boxes: Evidence from six new case studies

Abstract

Six subjects with a reading problem were tested on a variety of reading and other tasks including tests of phonological awareness and processing, short-term memory, visual analysis and synthesis, memory for faces and pictures, and matching of letters and shapes. The subjects demonstrated differences in their reading strategies, but these showed no relation to any differences in the patterns of deficit on non-reading tasks. Five of them showed severe problems on tasks involving phonological processing and short-term memory but the seventy of these was unrelated to reading strategy. There were some indications of visual weaknesses, but these were severe in only one subject who had a pronounced defect in memory for faces; there was no evidence that the visual weaknesses were consistently related to reading ability or strategy.

It is concluded that all the subjects in this sample (with one 'possible exception) had a deficit in phonological processing but adopted different strategies to cope with this when faced with the task of converting print to sound. Differences in strategy are likely to be affected by the relative efficiency of other cognitive processes, personality and introdctional factors.     

Short-term memory and sentence processing: Evidence from neuropsychology

Traditional models of memory assume that short-term memory, as measured by memory span, plays an important role in linguistic processing and the learning ofverbal information. Contradicting this view are findings from a brain-damaged patient, E.A., who, despite a verbal memory span of about two items, demonstrated normal sentence comprehension in a variety oftasks. She was, however, impaired whenever verbatim phonological information had to be maintained or learned. These results and those from other patients with reduced span suggest that the phonological storage capacity that is critical to memory span plays only a limited role in language processing, specifically in the maintenance and learning of phonological forms. Implications for models of short-term memory are discussed. It is argued that short-termmemory should be seen as deriving from the processing and retentive capacities of language processing modules, with span tasks drawing on only a subset of these modules.     

Deficits in verbal long-term memory and learning in children with poor phonological short-term memory skills

Possible links between phonological short-term memory and both longer term memory and learning in 8-year-old children were investigated in this study. Performance on a range of tests of long-term memory and learning was compared for a group of 16 children with poor phonological short-term memory skills and a comparison group of children of the same age with matched nonverbal reasoning abilities but memory scores in the average range. The low-phonological-memory group were impaired on longer term memory and learning tasks that taxed memory for arbitrary verbal material such as names and nonwords. However, the two groups performed at comparable levels on tasks requiring the retention of visuo-spatial information and of meaningful material and at carrying out prospective memory tasks in which the children were asked to carry out actions at a future point in time. The results are consistent with the view that poor short-term memory function impairs the longer term retention and ease of learning of novel verbal material.     

阅读障碍儿童汉字认知特点研究

运用多重评估法从760名小学3年级学生中选取了30名阅读与记字困难学生和30名正常学生为被试,分别研究了儿童视觉能力、听知觉能力和字形-音及字形义通道联结能力的识字认知特点。研究结果表明,阅读障碍儿童基本语音辩别能力不存在落后,而在视觉辨别、字形长时记忆、语音短时记忆以及形音和形义联结长时记忆上都存在程度不同的落后。研究还发现,阅读障碍儿童具有对汉字做浅层次机械加工和视觉加工的倾向。     

Deficits in verbal long-term memory and learning in children with poor phonological short-term memory skills

Possible links between phonological short-term memory and both longer term memory and learning in 8-year-old children were investigated in this study. Performance on a range of tests of long-term memory and learning was compared for a group of 16 children with poor phonological short-term memory skills and a comparison group of children of the same age with matched nonverbal reasoning abilities but memory scores in the average range. The low-phonological-memory group were impaired on longer term memory and learning tasks that taxed memory for arbitrary verbal material such as names and nonwords. However, the two groups performed at comparable levels on tasks requiring the retention of visuo-spatial information and of meaningful material and at carrying out prospective memory tasks in which the children were asked to carry out actions at a future point in time. The results are consistent with the view that poor short-term memory function impairs the longer term retention and ease of learning of novel verbal material.     

Impaired verbal short-term memory in Down syndrome reflects a capacity limitation rather than atypically rapid forgetting

Individuals with Down syndrome suffer from relatively poor verbal short-term memory. Recent work has indicated that this deficit is not caused by problems of audition, speech, or articulatory rehearsal within the phonological loop component of Baddeley and Hitch's working memory model. Given this, two experiments were conducted to investigate whether abnormally rapid decay underlies the deficit. In a first experiment, we attempted to vary the time available for decay using a modified serial recall procedure that had both verbal and visuospatial conditions. No evidence was found to suggest that forgetting is abnormally rapid in phonological memory in Down syndrome, but a selective phonological memory deficit was indicated. A second experiment further investigated possible problems of decay in phonological memory, restricted to item information. The results indicated that individuals with Down syndrome do not show atypically rapid item forgetting from phonological memory but may have a limited-capacity verbal short-term memory system.     

Short-term memory impairment and unilateral dichotic listening extinction in a child with Landau-Kleffner syndrome: auditory or phonological disorder?

The neuropsychological profile of a child with a Landau-Kleffner syndrome is presented here. The observed cognitive difficulties included verbal short-term memory and seemed partially compensated for when the experimental assessments bypassed the auditory channel. This case study is especially challenging since the child, whose phonological skills were quite efficient and who exhibited a dichotic listening unilateral extinction, had developed average reading and spelling abilities. The fact that B.E.'s performance on memory tasks was quite poor when the stimuli were presented auditorily and more efficient when the stimuli were presented visually, strongly suggests that the observed memory impairment was due to a deficit at the level of cortical auditory processing. B.E.'s phonological skills were efficient, suggesting a neuropsychological dissociation between phonological ability and auditory processing. The fact that B.E. dramatically recovered language and easily acquired reading and spelling accounts for the hypothesis that compensatory strategies allowed him to develop phonological skills from predominantly visual input.     

Nonword repetition in specific language impairment: More than a phonological short-term memory deficit

The possible role of phonological short-term memory in the nonword repetition deficit of children with specific language impairment (SLI) was investigated in a study comparing serial recall and nonword repetition of sequences of auditorily presented CV syllables. The SLI group showed impairments in both serial recall and nonword repetition relative to typically developing children of the same age, however the SLI deficit in nonword repetition was greater and persisted even when differences on an independent measure of short-term memory were taken into account. These findings cannot be readily explained in terms of a sole deficit in short-term memory, and point instead to differences between the serial recall and nonword repetition paradigms as potential factors contributing to this disorder of learning.     

Phonological Short-term Memory and the Learning of Novel Words: The Effect of Phonological Similarity and Item Length

The investigation of a patient with a selective impairment of phonological short-term memory has recently provided evidence that this system may be involved in long-term learning of novel words, for which a pre-existing semantic representation is not available (Baddeley, Papagno, & Vallar, 1988). The present series of experiments in normal subjects explored this hypothesis. We assessed the effects of phonological similarity and item length, which reflect the operation of the phonological short-term store and the rehearsal component of verbal memory, upon paired associate long-term learning of auditorily presented words and non-words. Phonological similarity affected the learning of novel words more than known words (Experiment 1); when a delay was interposed between presentation and recall, the disruptive effect was confined to novel words (Experiment 2). Also word length disrupted the learning of novel words, but not of known words (Experiment 3). These results tie in with neuropsychological evidence to suggest a role for phonological short-term memory in the learning of new words, and they have developmental implications for the study of language acquisition.     

Is the attentional blink effect located in short-term memory?

The attentional blink (AB) effect is characterized by a failure to detect a second target following the identification of a previous target in a RSVP stream. This effect has been attributed to capacity limitations at a central level of visual information processes. Postperceptual models suppose that the AB locus is located in short-term memory. To test this hypothesis, we investigated the influence of a short-term memory deficit on the AB effect in a patient with such a deficit. The three main results of this study are (1) the persistence of an AB effect, (2) a large number of T1 missed identifications and (3) a T2 detection deficit for a specific delay (367 ms). These results indicate that a short-term memory deficit disrupts the processing of each target (T1 and T2) but does not product an abolition of the AB effect.     

Impairment of the visuo-spatial sketch pad

A case study is presented of a female patient, ELD, who has difficulty in the immediate recall of short sequences of visuo-spatial material following a right-hemisphere aneurysm. Despite poor performance on tasks such as the Brooks Matrix and the Corsi Blocks, ELD is good at the immediate serial recall of letters even when presentation modality is visual and shows effects of phonological similarity and articulatory suppression. This pattern of performance represents a double dissociation from that which has been observed with the short-term memory patient PV (Vallar & Baddeley, 1984), who is extremely poor at serial recall of verbal material but shows no visual memory impairment. It is argued that ELD has an impairment to the visuo-spatial component of working memory (Baddeley, 1986) in the absence of any phonological loop deficit. Further investigation reveals that ELD performs poorly on mental rotation tasks and finds it difficult to use imagery mnemonics, but has no difficulty in retrieving visuo-spatial information from long-term memory so long as it was learnt before her illness.     

"The W and M are mixing me up": use of a visual code in verbal short-term memory tasks

When normal participants are presented with written verbal short-term memory tasks (e.g., remembering a set of letters for immediate spoken recall) there is evidence to suggest that the information is re-coded into phonological form. This paper presents a single case study of MJK whose reading follows the pattern of phonological dyslexia. In short-term memory tasks MJK does not phonologically re-code written materials but, it is argued, uses a visual code. There are three main lines of evidence for this, (a) MJK tends to substitute visually similar items for one another, (b) her performance is better with visual than auditory stimuli, and (c) she is able to remember numbers (e.g., 8) better than written words (e.g., eight). Investigation of short-term memory in others with phonological dyslexia is warranted.     

The cognitive and neurological basis of developmental dyslexia: a theoretical framework and review.

It is argued that developmental dyslexics have difficulty in accessing the meaning of written words via phonological recoding, although they can successfully access meaning by a direct visual route. This difficulty with phonological recording is explained in terms of a short-term memory deficit. It is suggested that developmental dyslexia is a genetically-based dysfunction of the inferior parietal lobule and evidence is reviewed that this region is important in both reading and short-term memory. Implications for remedial instruction are discussed.     

The relationships among verbal short-term memory, phonological awareness, and new word learning: evidence from typical development and Down syndrome

This study examined the correlates of new word learning in a sample of 64 typically developing children between 5 and 8 years of age and a group of 22 teenagers and young adults with Down syndrome. Verbal short-term memory and phonological awareness skills were assessed to determine whether learning new words involved accurately representing phonological information in memory. Results showed a relationship between verbal short-term memory measures and typically developing individuals’ ability to learn the phonological form of novel words but not their ability to learn the physical referent of new words. Similarly, individuals with Down syndrome showed impaired verbal short-term memory and impaired form but not referent learning. Together, these findings specify the circumstances in which an accurate phonological representation within short-term memory is required for new word learning.     

Spatial and visual working memory ability in children with difficulties in arithmetic word problem solving

Although various studies support the multicomponent nature of visuospatial working memory, to date there is no general consensus on the distinction of its components. A difference is usually proposed between visual and spatial components of working memory, but the individual roles of these components in mathematical learning disabilities remains unclear. The present study aimed to examine the involvement of visual and spatial working memory in poor problem-solvers compared with children with normal level of achievement. Fourth-grade participants were presented with tasks measuring phonological loop, central executive, and visual versus spatial memory. In two separate experiments, both designed to distinguish visual and spatial component involvement, poor problem-solvers specifically failed on spatial—but not visual or phonological—working memory tasks. Results are discussed in the light of possible working memory models, and specifically demonstrate that problem-solving ability can benefit from analysis of spatial processes, which involves ability to manipulate and transform relevant information; instead, no benefit is gained from the analysis of visual pictorial detail.     

Verbal Short-term Memory and Vocabulary Learning in Polyglots

Polyglot and non-polyglot Italian subjects were given tests assessing verbal (phonological) and visuo-spatial short-term and long-term memory, general intelligence, and vocabulary knowledge in their native language. Polyglots had a superior level of performance in verbal short-term memory tasks (auditory digit span and nonword repetition) and in a paired-associate learning test, which assessed the subjects' ability to acquire new (Russian) words. By contrast, the two groups had comparable performance levels in tasks assessing general intelligence, visuo-spatial short-term memory and learning, and paired-associate learning of Italian words. These findings, which are in line with neuropsychological and developmental evidence, as well as with data from normal subjects, suggest a close relationship between the capacity of phonological memory and the acquisition of foreign languages.     

Short-term memory and verbal learning with auditory phonological coding defect: a neuropsychological case study.

A patient is described with a rarely reported linguistic syndrome: he could repeat words but not nonwords. The patient produced semantic paraphasias in repetition and could read both words and nonwords flawlessly. His basic difficulties were localized in auditory phonological coding, identifying a clinical picture called "phonemic deafness." Short-term memory and verbal learning results suggested that a standard, selective short-term memory defect can be induced by auditory phonological coding deficits as well as by "pure" short-term memory capacity limitation and other phonological deficits. Findings also provided evidence that lexical-semantic code can allow normal verbal learning.     

Deficit in phonological processes: a characteristic of the neuropsychological profile of children with NF1

Learning disabilities are one of the most frequent complications of neurofibromatosis type 1 (NF1) in children. Studies of the effects of the neurocognitive deficit on academic performance are relatively rare, owing to the small size of the populations concerned. However, research is needed to develop effective rehabilitation programs. In the present study, we explored the impact of a possible phonological deficit on the reading abilities of children with NF1. A multicenter, cross-sectional study was conducted in France on two groups of 75 children with or without NF1 aged 8–12 years, matched for age, sex, handedness, and reading level. All participants underwent a neuropsychological evaluation to assess their general cognitive level, reading skills, phonological processes, visuoperceptual abilities, and attentional capacity. Phonological skills were assessed by means of two phonological awareness tasks and one short-term memory task. In the group of children with NF1, 41% had reading difficulties. Phonological processes were impaired in this group, compared with the children without NF1. Similar differences were found for a phoneme deletion task after adjustment for reading difficulties, IQ level, and visuoperceptual abilities. Phonological awareness, but not phonological short-term memory, was impaired in children with NF1, and not just those whose reading was impaired. Results suggest that children with NF1 have a phonological awareness deficit, whatever their reading level. Identification of reduced phonological skills may warrant the implementation of a specific rehabilitation program before early reading difficulties emerge.