Working Memory and Neurodevelopmental Disorders

Tracy Packiam Alloway, Susan E. Gathercole

• Publisher: Psychology Press
• Year: 2012
• ISBN:
  9781135421342
• Edition: 1
• Topic: Psychology
• Subtopic: History & Theory in Psychology
• Index: Psychology

Short-term or working memory - the capacity to hold and manipulate information mentally over brief periods of time - plays an important role in supporting a wide range of everyday activities, particularly in childhood. Children with weak working memory skills often struggle in key areas of learning and, given its impact on cognitive abilities, the identification of working memory impairments is a priority for those who work with children with learning disabilities.

Working Memory and Neurodevelopmental Disorders supports clinical assessment and management of working memory deficits by summarising the current theoretical understanding and methods of assessment of working memory. It outlines the working memory profiles of individuals with a range of neurodevelopmental disorders (including Down's syndrome, Williams syndrome, Specific Language Impairment, and ADHD), and identifies useful means of alleviating the anticipated learning difficulties of children with deficits of working memory.

This comprehensive and informative text will appeal to academics and researchers in cognitive psychology, neuropsychology and developmental psychology, and will be useful reading for students in these areas. Educational psychologists will also find this a useful text, as it covers the role of working memory in learning difficulties specific to the classroom.

1   Introduction

Tracy Packiam Alloway

Working memory has been an extremely influential concept that in the last 30 years has guided empirical investigations and understanding of adult and developmental cognition, and, more recently, developmental disorders. The purpose of this book is to bring together researchers involved in applying and developing understanding of working memory in the context of a variety of developmental disorders, from learning disabilities to Williams syndrome.

Current understanding of working memory stems in large part from the working memory model initially advanced in 1974 by Baddeley and Hitch. At the core of this model is the central executive, responsible for controlling resources and monitoring information processing. A component responsible for integrating information from the subcomponents of working memory and long-term memory, known as the episodic buffer, has been recently proposed (Baddeley, 2000). Other cognitive functions have subsequently been associated with the central executive (Baddeley, 1996). These factors, known as attentional or executive functions, are thought to enable a person to successfully engage in independent and purposeful behaviours. These include the ability to suppress irrelevant information, shifting between multiple tasks, and monitoring and revising information held in working memory. In this volume, executive skills are discussed by Roodenrys with respect to children with attention deficit hyperactivity disorder, by Passolunghi in children with mathematical difficulties, and by Belleville et al. in autistic spectrum disorder.

The central executive is supported by two separate storage systems: The phonological loop functions as a temporary store for phonological information, and the visuospatial sketchpad is where visual and spatial representations are temporarily stored and manipulated. The chapters by Pickering and Alloway discuss the specificities of these storage components and their relationship to children with dyslexia and developmental coordination disorder (also known as dyspraxia), respectively.

Another key conceptualization of working memory has been put forward by Cowan (2005), according to which working memory is not a distinct entity, but rather an activated component of long-term memory. Other models of working memory incorporate concepts of attention in memory (e.g., Engle, Kane, & Tuholski, 1999) and temporal duration in performing memory tasks (e.g., Barrouillet, Bernardin, & Camos, 2004). The chapter by Vukovic and Siegel discusses reading comprehension difficulties in light of different working memory models.

Traditionally, working memory capacity is measured using complex span tasks (also known as dual tasks), which require the individual to engage in some form of immediate processing, such as reading sentences or mental arithmetic (e.g., Daneman & Carpenter, 1980) while maintaining information for recall. In contrast, short-term memory tasks only measure storage capacity. Such tasks include ones where the individual has to immediately recall a sequence of verbal or visuospatial information in the order it was presented. Measures of working-memory capacity are strongly related to performance in complex cognitive activities such as reasoning, grammatical understanding, reading comprehension, and mathematical skills. Children with weak working memory skills often struggle to reach expected levels of attainment in key educational domains such as literacy and mathematics, and may have learning difficulties that are sufficiently severe as to be recognized as having special educational needs.

Given the impact of working memory deficits on the child’s abilities to acquire knowledge, develop crucial skills and benefit from formal education, the identification of working memory impairments is a priority for many working with young people with learning disabilities. One of the aims of this edited book is to support clinical assessment and management of working memory deficits by summarizing current theoretical understanding and methods of assessment of working memory, characterizing working memory function in individuals with a range of neurodevelopmental disorders, and identifying useful means of alleviating the anticipated learning difficulties of children with deficits of working memory.

Empirical tools and concepts developed in this dynamic field of research have proven extremely valuable in illustrating the characteristics of developmental disorders. This book also reflects the convergence of interest from different academic and professional groups, such as educators, cognitive psychologists, special needs coordinators, and developmental psychopathologists, in the role of working memory in atypical developmental populations. Drawing from the expertise of leading researchers in this area, this text integrates information from both normal and abnormal development to distinguish the contribution of working memory from general cognitive deficits during childhood.

The chapter by Pickering on dyslexia provides an overview of verbal and visuospatial memory deficits in children with dyslexia. She also discusses assessment tools such as the Working Memory Test Battery for Children (WMTB-C; Pickering & Gathercole, 2001) and the Automated Working Memory Assessment (AWMA; Alloway, Gathercole, & Pickering, 2004) that provide useful diagnostic information on the nature of working memory deficits in a dyslexic cohort.

Wagner and Muse provide a slightly different view of dyslexia. Specifically, they outline how developmental dyslexia is distinguished from acquired dyslexia, and can be characterized by deficits in both phonological short-term memory and phonological awareness. In particular, performance on short-term memory tasks such as nonword repetition is discussed in light of phonological coding skills and lexical knowledge.

In a related topic, Swanson presents meta-analyses of studies on reading disabilities and verbal working memory and short-term memory deficits. The findings indicate that working memory plays a significant role in accounting for individual differences in reading abilities. In particular, children with reading deficits struggle with tasks that place high demands on processing skills such as inhibiting conflicting information and updating relevant information.

A key feature in the literature in reading disabilities is that children can have adequate word reading skills, yet struggle in reading comprehension. Vukovic and Siegel review the research on the role of working memory in this cohort. These children have a generalized working memory deficit, and struggled with verbal working memory tasks that involved both words and numbers. This suggests that it is not purely a language deficit that characterizes children with reading comprehension difficulties, but also difficulty with the simultaneous process of storing and manipulating information.

A learning disability that can cooccur in children with reading problems is arithmetic learning disability. Passolunghi discusses the prevalence and criteria for such a diagnosis. She outlines the associations between working memory and different aspects of mathematical knowledge, such as simple arithmetic computations and arithmetic word problems. In addition, she also addresses executive skills such as inhibition, updating, and shifting in children with arithmetic learning disability.

Children with specific language impairment (SLI) are reliably identified with a short-term memory task, nonword repetition. Archibald and Gathercole extend the current understanding of memory impairments in this population to indicate that marked deficits in both verbal short-term memory and verbal working memory may be even more severe than the language impairments that form the basis for their diagnosis. Implications of these memory deficits for effective learning support for children with SLI and other related learning difficulties are considered.

An area that has received very little attention until recently is the working memory profiles of children with motor coordination difficulties (also known as dyspraxia or developmental coordination disorder). Alloway reviews current research which indicates that this cohort typically has normal verbal IQ scores but exhibits specific deficits in performance IQ tasks. New evidence on working memory skills is also presented. The findings indicate that children with motor coordination difficulties performed poorly in both verbal and visuospatial memory tasks, but had a selective deficit in visuospatial working memory tasks.

Roodenrys reviews differential findings on verbal and spatial working memory impairments in children with attention deficit hyperactivity disorder (ADHD). He suggests that there is some evidence of a verbal working memory impairment, as well as comorbid reading disability. There is stronger evidence for an impairment in spatial working memory. These findings are discussed in light of research on poor inhibition skills.

Children with autistic spectrum disorder can exhibit a range of differential cognitive patterns. Belleville, Ménard, Mottron, and Ménard assess current models of the cognitive features that characterize autism. An interesting finding is that short-term memory skills among savant persons tend to be higher than in a normal population, using a range of material such as pseudowords, function words, and numerical material. There is some evidence that the ability to shift attention from one task to another is impaired in children with autism.

The chapter by Jarrold, Purser, and Brock illustrates how poor short-term memory skills in children with Down syndrome are manifest in different cognitive tasks. In particular, this chapter reviews vocabulary performance in this cohort and whether performance is constrained by individuals’ relatively poor verbal short-term memory, or related factors such as hearing difficulties, speech production problems, and language delay, which are also associated with this condition.

Children with Williams syndrome are often found to have dissociable cognitive profiles in verbal and visual memory. Rowe and Mervis establish the relative strength in verbal short-term memory and language and severe weakness in visuospatial skills in children with Williams syndrome across different studies. This strength in verbal memory abilities is strongly related to grammatical ability and vocabulary ability, and is an association that continues to be significant through adolescence for children with Williams syndrome.

Taken together the chapters illustrate how the concept of working memory has been strongly influenced by not only experimental psychology, but also by clinical and neuropsychological research. It is intended that this volume will present the reader with current research in this area and how it pertains to developmental disorders. In addition, the inclusion of remedial approaches provide a background to emerging research on working memory intervention strategies.

REFERENCES

Alloway, T. P., Gathercole, S. E., & Pickering, S. J. (2004). The Automated Working Memory Assessment [Test battery]. Available from authors.

Baddeley, A. D. (1996). Exploring the central executive. Quarterly Journal of Experimental Psychology, 49A, 5–28.

Baddeley, A. D. (2000). The episodic buffer: A new component of working memory? Trends in Cognitive Sciences, 4, 417–423.

Baddeley, A. D., & Hitch, G. (1974). Working memory. In G. A. Bower (Ed.), Advances in research and theory: Vol. 8. The psychology of learning and motivation (pp. 47–89). New York: Academic Press.

Barrouillet, P., Bernardin, S., & Camos, V. (2004). Time constraints and resource sharing in adults’ working memory spans. Journal of Experimental Psychology: General, 133, 83–100.

Cowan, N. (2005). Working memory capacity. New York: Psychology Press.

Daneman, M., & Carpenter, P. A. (1980). Individual differences in working memory and reading. Journal of Verbal learning and Verbal Behavior, 19, 450–466.

Engle, R. W., Kane, M. J., & Tuholski, S. W. (1999). Individual differences in working memory capacity and what they tell us about controlled attention, general fluid intelligence and functions of the prefrontal cortex. In A. Miyake & P. Shah (Eds.), Models of working memory: Mechanisms of active maintenance and executive control (pp. 102–134). London: Cambridge Press.

Pickering, S. J., & Gathercole, S. E. (2001). The Working Memory Test Battery for Children. London: Harcourt Assessment.

2 Working memory in dyslexia

Susan J. Pickering

OVERVIEW

The focus of this chapter is the nature of immediate memory in developmental dyslexia and the contribution that a dynamic, multi-component model of working memory is able to make to the systematic study of individuals with dyslexia. The chapter begins by outlining some of the reasons why dyslexia is a difficult issue for scientific study: the lack of consensus on definition, cause, and even about who is dyslexic and who is not. There follows a description of a popular conceptualisation of immediate memory (the modal model) and a description of the findings of research investigating immediate verbal and visual memory that was carried out largely in the context of this model.

The second half of the chapter introduces the Baddeley and Hitch (1974) working memory model and argues that although this model has been in existence for over 30 years, it has not been employed in the systematic study of dyslexia until about a decade ago, and studies of this kind are still relatively few in number. Although the early data on immediate verbal and visual memory in dyslexia can be mapped onto the two “slave systems” of working memory (the phonological loop and the visuospatial sketchpad), arguably the most significant contribution of the working memory model to the study of dyslexia has been the suggestion of a central executive component that is involved in the active processing of information in immediate memory and in a number of attentional processes. Evidence from studies that have specifically investigated the central executive functioning of dyslexics (and other poor readers) appears to indicate deficits in this part of the memory system.

The final section of the chapter describes a tool for measuring the working memory performance of children across the three components of the Baddeley and Hitch model. The Working Memory Test Battery for Children (WMTB-C) has been administered to children with dyslexia, and other related developmental disorders, in order to investigate the relative profile of strengths and weaknesses in the three working memory components. Results from a series of small studies of these populations allows the investigation of two important questions: Do individuals with dyslexia have impairments in specific components of working memory, and, if so, do individuals with other developmental disorders show similar or different working memory profiles to the dyslexic population. The findings from these studies are discussed with respect to the theoretical and practical implications of detailed working memory assessment in individuals with developmental learning problems.

INTRODUCTION

When one asks the seemingly simple question: “Do individuals with dyslexia have problems with working memory?” one might expect a fairly simple answer – “yes” or “no”. However, answering this question has turned out to be far less simple than one might expect. Many individuals with dyslexia (and those around them) will be very clear that their working memory is poor and that this is a key feature of their dyslexic difficulties. Ask practising psychologists with experience of assessing dyslexia, and they are also likely to agree that many of the individuals that they see have problems with immediate memory, as evidenced by poor scores on the Digit Span sub-tests of the Wechsler Intelligence Scale for Children (Wechsler, 1996), or other similar measures (e.g. Turner, 1997). However, ask a researcher about the nature of working memory in dyslexia, and the issue becomes more complex. Despite over 30 years of investigation in this area, there is still little consensus on the status of working memory in individuals with dyslexia, and whether deficits that are observed play a causal role in the dyslexia syndrome.

Developmental dyslexia is itself a difficult disorder to define. Indeed there is no one agreed definition of the problem, despite over 100 years of attempts to describe and explain it. Many would agree that the striking feature of individuals with dyslexia is their pronounced problems with acquiring and using literacy...

Table of contents

• Cover
• Title
• Copyright
• Contents
• List of contributors
• List of figures and tables
• Foreword
• 1 Introduction
• 2 Working memory in dyslexia
• 3 Short-term memory deficits in developmental dyslexia
• 4 Working memory and reading disabilities: Both phonological and executive processing deficits are important
• 5 The role of working memory in specific reading comprehension difficulties
• 6 Working memory and arithmetic learning disability
• 7 Short-term memory and working memory in specific language impairment
• 8 Working memory skills in children with developmental coordination disorder
• 9 Working memory function in attention deficit hyperactivity disorder
• 10 Working memory in autism
• 11 Short-term memory in Down syndrome
• 12 Working memory in Williams syndrome
• Author index
• Subject index