Assessment in Neuropsychology

John R. Beech, Leonora Harding

• Editorial: Routledge
• Año: 2002
• ISBN:
  9781134793761
• Edición: 1
• Categoría: Psychology
• Categoría: History & Theory in Psychology

Assessment in Neuropsychology is a practical and comprehensive handbook for neuropsychologists and other professionals who use neuropsychological tests in their everyday work. Each chapter outlines assessment procedures for specific functions such as language, visual impairment and memory. Case studies are used to illustrate their applications, pointing the professional towards the most relevant assessments for their clients' needs, and where and how they can be acquired. Leonora Harding and John R. Beech also explore new developments in neurological and neuropsychological assessment and clarify legal issues.
Assessment in Neuropsychology will be an invaluable sourcebook for clinical psychologists, neurologists and other professionals as well as those in training.

Part I

1
INTRODUCTION

The aims of neuropsychological assessment

J.Graham Beaumont

The essential aim of any neuropsychological assessment is an improvement in the condition of a client who has suffered some form of damage to the nervous system. However, within that general intention there are a number of ways by which the improvement might be achieved and in consequence a variety of forms which the assessment may take. Although there is a range of current practices within neuropsychological assessment, it is important to maintain a clear idea of the precise goal of a particular assessment procedure and the appropriate form which it should, as a consequence, take.

There are two basic forms of the neuropsychological assessment. They are often confused, but it should be recognized that they are fundamentally different, and have different applications with respect to the specific goals of a particular investigation. They are the generation of structural descriptions, and that of functional descriptions, of the client’s present status.

STRUCTURAL DESCRIPTIONS

The object of a neuropsychological assessment which generates a structural description is to provide a report of the changes in the client’s nervous system in neurological, anatomical terms. Until recently this was the more important of the two forms of neuropsychological investigation.

The history of scientific neuropsychology over the past century shows that the principal concern during much of that period has been the discovery of brain-behaviour relationships. The techniques of clinical neuropsychology (see below) have primarily provided evidence about the association between anatomical structures and behavioural functions. The obvious application of this scientific knowledge was to observe the dysfunctional changes in specific behaviours and draw inferences about the gross neuroanatomical changes which can be presumed to have produced them.

Applications of this principle are still of some value, but they had greater importance before the introduction of computerized axial tomography (CAT scans) in the 1970s and the subsequent development of more refined techniques of imaging the brain. In that period the physical investigations open to neurologists and neurosurgeons were of inferior validity, and psychological evidence could make a significant contribution to the localization of a tumour, the assessment of the degree of cortical atrophy, or the topography of the effects of a stroke. Neurosurgeons might also be concerned about the lateral representation of psychological functions when deciding, for example, how radical the resection of the anterior temporal lobe might safely be made in a case of unilateral anterior lobectomy (Beaumont, 1983).

FUNCTIONAL DESCRIPTIONS

An alternative form of description can be generated in purely psychological functional terms. Such a description is without reference to neuroanatomical structures, and forms an account, employing psychological models, of the client’s relative abilities across a spectrum of behavioural functions.

Functional descriptions have assumed much greater importance in the last ten or fifteen years, for three reasons. The first, already discussed, is the decline in the importance of psychological evidence in the structural identification of a client’s lesion. The second is a growth of interest, long overdue, in behavioural approaches to management and remediation. The third, and most significant, is the development of cognitive neuropsychology as a distinct approach within neuropsychology. The generation of cognitive models of normal and abnormal performance has facilitated the description of a client’s functional status in terms which need make no reference to anatomical localization.

These two forms of description are rarely so clearly separated, and of course there are logical interrelationships which permit some degree of mapping from one to the other. Possessing a structural description allows inferences to be made about the relative status of different behavioural systems; a functional description will often permit some assessment of the neuroanatomical basis of the various dysfunctions. Nevertheless, each form has its own peculiar merits and application to specific assessment goals.

SPECIFIC ASSESSMENT GOALS

There are five main goals in neuropsychological assessment by which clinical improvement in the client’s status might be achieved.

Medical intervention

Appropriate medical intervention, whether by surgery, drug treatment, or other forms of physical management, depends upon accurate diagnosis of the client’s neurological state. Psychological evidence can contribute to this by assisting in the localization and identification of the client’s lesion. While this role may have declined in recent years, psychological test results are still relevant to many medical decisions. With this goal it is structural descriptions which are generally more important.

Psychological intervention

Psychological interventions are less well established but there has been a rapid expansion of these techniques in recent years. They include: specific remedial therapeutic approaches; ways in which the client’s orientation and concentration can be improved; techniques to assist clients to overcome handicaps in, for example, memory; and the modification of general behavioural disorders. It is clearly not possible to apply psychological interventions aimed at specific behavioural problems unless the therapist possesses a good description of the client’s functional psychological state. Functional descriptions are therefore of prime importance.

Management

The general management of clients with a neurological disorder involves a variety of forms of support, some specifically medical, some nursing, some psychological, with contributions from other specialisms. Each of these may benefit from a neuropsychological description of the client’s status, and structural and functional descriptions may contribute differentially to the management of the client’s disorder.

Prognosis

A particular aspect of the management of the client is the formulation of a behavioural prognosis. Depending upon the disorder, this may be the eventual level of function which might be regained, or it may be the likely course of a disease as it progresses. The prognosis may be relevant to management decisions, and is also of great importance to the client and to relatives and carers. Functional descriptions are likely to be of greater value.

Monitoring change

A particularly valuable goal of neuropsychological assessment is the regular monitoring of behavioural changes, often conducted as a contribution to management, to the evaluation of interventions, or to the refinement of prognosis. Although not necessarily formulated in functional terms, the description of behavioural changes is likely to be more precise and useful if constructed as a functional description.

There are, of course, other reasons for conducting neuropsychological assessments. Scientific enquiry is a valid reason for the investigation of clients providing that the client’s individual interests are respected; there may be medico-legal reasons for determing the client’s functional status; and the legitimate concerns of relatives and carers must also be taken into account, as well as, occasionally, those of a wider community. However, these reasons normally share features with the goals of assessment which have already been identified, and which form the basis of contemporary practice in clinical neuropsychology. (For general reviews see: Beaumont, 1983; Crawford et al., 1992; Golden and Vicente, 1983; Walsh, 1985.)

APPROACHES IN NEUROPSYCHOLOGY

The current conceptual basis of clinical neuropsychology is complex, and is rarely stated explicitly. It is complex as a result of the variety of influences which have acted upon it over the last century, and it is still in rapid evolution. Much is implicit in the clinical and research procedures which neuropsychologists employ, and close examination of the conceptual assumptions which underlie these procedures would fail to reveal a consistent or coherent underlying philosophy.

The most fundamental problem stems from a failure to take a clear position on the essential issue, which is that of the relationship between mental and physiological events: the ‘mind-body problem’. Most contemporary neuropsychologists adopt, by default, the position of ‘emergent psychoneural monism’: accepting that mental properties in some way emerge out of neural events and can be correlated with them, but reserving the possibility that mental properties may have an existence which is to some degree independent of physiological events.

This compromise allows neuropsychologists to accept the relevance of anatomical and physiological data to neuropsychological states, but avoids the reductionist trap of shifting the focus of attention to ever more elementary biological mechanisms. It permits, for instance, the sensations of taste to be explained by neural mechanisms, but the taste as perceived to be a mental property which is associated with, but not wholly determined by, the neural apparatus. The detection of sugars in biting an apple is carried out by the brain, but the sweetness is in the mind.

This is not an entirely satisfactory position, and there are obvious philosophical objections to it when it is stated so baldly. It is also inconsistent with much that neuropsychologists actually do: for instance, by discussing the localization of higher mental abilities such as gnostic functions. (For an unusually clear discussion of these issues see Bunge, 1980).

Models of neuropsychological function

Historically, neuropsychology began by adopting a localizationist approach. The early neuropsychologists, in the second half of the nineteenth century, believed a particular part of the brain to be responsible for a specific psychological function, and set about identifying the localization of each function.

However, from the start, there were opponents who supported the alternative equipotential theory: that while sensory input is localized, perception involves the whole brain, and that the effects of brain lesions depend upon their extent and not upon their location.

Both approaches fail, in some way, to account for the relevant evidence. It is certainly possible to demonstrate some degree of localization of higher functions, but not with the precision which is demanded by localization theory. The outcome has been that most neuropsychologists now ascribe to a third, intermediate, approach known as interactionist theory. This theory probably originates from the work of Hughlings Jackson, who argued that ‘higher’ abilities are built up by combining a number of more basic functions. Damage to the brain affects the more basic level of component skills and so has an effect upon various higher functions to the extent that they depend upon the more basic skills.

Generally accepted findings that no function or learning process is entirely dependent on any particular area of cortex, and that each part within the brain plays an unequal role in different functions, support the interactionist position. In practice, interactionist theory is linked to the concept of ‘regional equipotentiality’: that at the level of neuropsychological analysis relatively specific functions can be assigned to regions of the cortex, but that a degree of equipotentiality operates within this region. This is a pragmatic, rather than a scientifically justified, position.

The research strategies adopted by neuropsychologists, and the clinical procedures which are derived from them, are based upon the interactionist approach. Clinical cases are observed for the functional deficits which they demonstrate, and these deficits are correlated with the nature of the lesion, including its location. A typical research design selects groups of patients with particular lesions which can be classified along a series of dimensions (location, size, diffusion, chronicity, pathology), and these groups are contrasted with respect to performance on a particular function.

A particular refinement of this approach is the use of ‘double dissociation’ ( Weiskrantz, 1968). Double dissociation is demonstrated where lesions of area A affect function X more than function Y, while lesions of area B affect function Y more than function X. This is a useful analytic concept, but relies upon relatively strict and stable localization, and is often difficult to apply in a complex clinical situation.

Although the logic of these approaches is simple, there is a variety of methodological difficulties in putting them into practice. Their success is also dependent upon the adequacy of the interactionist theory which is itself a slightly uncomfortable compromise between competing conceptual approaches.

Cognitive psychology and neuropsychology

There has inevitably been a close association between neuropsychology and experimental psychology, more latterly as cognitive psychology. The information and models derived from the study of psychological abilities in normal states is of obvious relevance to the study of these functions in abnormal states.

The dominant approach incorporated in information-processing models has been transferred into clinical neuropsychological models and procedures. In its most general form, what we might call the ‘telephone exchange model’, it assumes that sensory information comes into the brain in primary (highly localized) cortex, from where it is routed to secondary cortex for the processes of perception and elaboration, and then on to tertiary association cortex, where higher functions are performed. This is consistent with the interactionist approach, and allows information to be routed among different basic processing modules which are combined to generate higher-level functions. The effect of lesions is supposed both to impair the function of specific basic modules and to interrupt the connections among them.

The development of more sophisticated models in cognitive psychology in recent years has both benefited from clinical neuropsychological data, and provided more elaborate conceptual structures by which individual clients may be assessed (Ellis and Young, 1989; McCarthy and Warrington, 1990; Shallice, 1988). It is currently having a profound effect upon clinical neuropsychology because it has shifted the research emphasis from studies of groups of similar patients to the intensive study of individual cases. A clear example is a recent lengthy monograph which deals exclusively with the single-word processing deficits of an individual client (Howard and Franklin, 1988). This shift is generating a vigorous debate about the relative merits and applications of group versus single-case studies in neuropsychology. It is too early to assess the full impact of the cognitive neuropsychological approach in clinical applications, but it will u...

Índice

• COVER PAGE
• TITLE PAGE
• COPYRIGHT PAGE
• BOXES
• FIGURES
• CONTRIBUTORS
• SERIES EDITORS’ PREFACE
• PART I
• PART II
• PART III
• ASSESSMENT PROCEDURES AND TESTS