Memory disorders in clinical practice

J. Neurolinguistics. Volume 5, Number 4,

Printed

pp. 439-447, 1990.

0911~6044/90

$3.00+.00

PergamonPress plc

in Great Britain

REVIEW

MEMORY DISORDERS IN CLINICAL PRACTICE. London: Butterworths, lw18,289pp.

By Narinder Kapur.

Reviewed by Sylvie Belleville’ and And& Roth Leeours Centre Hospitalier Che-des-Neiges, Montreal3

Whether it is viewed from the point of view of the neurological or from that of the cognitive sciences, memory - human memory in the present context - is now conceived as a set of various systems and processes involved in the storage of information and its eventual retrieval. In cognitive terms, memory is therefore a basic function allowing the individual organism to use learned information in its adaptation to everyday situations and to maintain a sense of continuity over time. On the other hand, memory impairments of different types are among the most frequent manifestations of cerebral damage and, if only for that reason, the publication of a textbook tackling the problem of memory disorders in the optic inherent to clinical preoccupations certainly fulfils a major need. Narinder Kapur’s Memory disorders in clinical practice is thus meant to offer a general guide to clinicians involved in the assessment and management of patients with diseases impairing their mnesic abilities. The author underlines that, although he has written his book by reference to a clinical framework, his intention is to focus on objective studies of memory disorders. He also insists that, contrary to more classical handbooks on the same topic, his own provides guidance with regard not only to the amnesic syndrome but also to less severe and/or less pure disorders of memory: this point is well taken. Kapur’s book begins with three short sections, including a preface where he outlines his goal and a glossary in which he defines the key terms of his text. It is thereafter comprised of 10 very dense chapters, the first dealing with general issues and the other nine, parsed along the etiology dimension, with the various memory disorders that are currently recognized in neurological nosology. Two appendices providing relevant indications as to materials currently used in memory testing and remediation are presented at the end of the volume. Chapter 1 Entitled “Assessment of memory functioning,” the initial chapter presents the theoretical background upon which the book is founded and specifies the objectives

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of memory assessment in clinical practice. Classical oppositions such as “verbal” vs “non-verbal” memory are dealt with at this point, functions likely to be affected in memory impaired patients are identified, and memory testing instruments are defined. The author clarifies what will be the main focus of his book, that is, “retention of specific information which has been acquired in the recent past.” He therefore warns the reader that he will not place emphasis on deficits in the retention of overlearned material such as those observed in agnosia or aphasia (for a consideration of these aspects see for example, Ellis and Young 1988; Lecours and Belleville 1989; Peretz et al. in press). Involved and long (44 pages), this chapter provides a wealth of information concerning a large number of topics related to clinical memory disorders, ranging from description of mnesic impairments in different clinical and functional conditions to description of various memory testing batteries. The amount of information provided is indeed rather vast for the context of a single chapter and, as a matter of fact. the author sometimes diverges from the topic announced to be under discussion in given sections. It is for instance puzzling to find a discussion of retrograde amnesia in the section on everyday memory functioning (pp. 18-9), or else of forgetting rate in the section dealing with picture/object memory tasks (p. 32). Although Kapur does provide his reader with some notions related to contemporary memory theories and testing procedures, an explicit theoretical framework and the implications that it would entail are lacking. Chapter

2

Kapur’s first etiological choice is “Cerebrovascular disease.” He considers the effects of cerebrovascular diseases on mnesic functions from four standpoints : (1) arterial territories of the brain, (2) focal parenchymal lesions of vascular origin, (3) episodic disturbances, and (4) eventual improvement of memory disorders in cerebrovascular disease. Kapur’s apparent goal in this part of his book is to define a number of specific memory impairments in relation to particular brain lesions of vascular etiology. Even if one believes that such specific impairments are likely to emerge, this goal is not easy to achieve if only because the notions of arterial territories and of focal parenchymal lesions are widely overlapping, which inevitably generates repetitions given the plan of the chapter [a fact that the author himself acknowledges (p. 54)l. Another reason why this chapter is, in our opinion, the most difficult one for the reader is that it takes into account a large number of studies from which no clear unifying conclusion can be drawn. Chapter

3

In the following chapter, which bears on “Cerebral

tumours,”

Kapur reviews

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studies on the effect of cortical and subcortical tumours on memory functioning. His conclusion is that cortical tumours lead to memory dysfunctions similar to those caused by focal vascular lesions of comparable localizations. On the other hand, he points out that memory impairments are more severe when related to subcortical tumours than lesions, especially those located in or around the third ventricle. Chapter 4 Kapur then discusses the problem of “Penetrating head iJury” on the basis of studies bearing on a group of patients with focal brain wounds and relatively selective and isolated memory deficits. Since restricted penetrating head injuries produce lesions and deficits which may differ greatly from one patient to the other, such a group might in our opinion have constituted an ideal sample for an in-depth study of the functional architecture of memory through the single case approach [for a discussion of this approach, see for instance Shallice (1979, 1988) and Caramazza and McCloskey (1988)l. Nonetheless. and with the notable exception of the famous case N.A., Kapur’s chapter on penetrating head injuries deals mostly with the results of group studies. Chapter 5 “Blunt head injury” is the topic of the following chapter in which the author reviews and discusses pre- and post-traumatic amnesia, anterograde amnesia, rate of recovery and management of memory deficits within a most heterogeneous group of patients. According to Kaput’s review, it is mostly the long-term component of memory which is affected in blunt head injury. It is worth noting, however, that only the passive components of short-term memory - using the classical digit-span procedure - has been investigated among these patients with blunt head injuries. The attentional resource capacities of working memory (Baddeley 1986) have not been systematically investigated and might be diminished in these patients (Baddeley et al. 1987). Chapter 6 Kapur thereafter turns to “Degenerative, demyelinating and hydrucephalic dementias.” i.e. he discusses the memory disorders observed in patients with primary degenerative dementia, dementia associated with other neurological diseases such as Parkinson’s and Huntington’s, central nervous system demyelination, and hydrocephalus. Given that memory impairments are very often among the first symptoms of primary degenerative dementia, it does not come as a surprise that this sub-

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population is discussed at length. Unlike the memory disorders observed in other pathologies, those occurring in dementias of this type are not only comprised of an eventually severe long-term but also of a short-term memory impairment (diminished span, decreased Brown-Peterson procedure performance); tentative explanations as to the nature of the memory deficits in such dementias have been proposed (for a review see Morris and Kopelman 1986; Kaszniak 1986; and Lussier et al. 1990) and one is surprised that Kapur does not discuss the issue. His chapter nonetheless underlines the fact that distinct subtypes of cognitive impairments may exist in primary degenerative dementia. Kapur suggests that each subtype is likely to correspond to a distinct neuropathological pattern. As Vaidois et ai. (in press) have recently suggested, the existence of such clinical subtypes might, at least in part, be linked to the heterogeneity of normal cognitive aging. Be this as it may, the very existence of clinical subtypes obviously represents a critical fact for clinicians who are confronted daily with the differential diagnosis of demented patients whose cognitive disorders do not conform to the classical pattern of deterioration. Chapter 7 The seventh chapter of Kapur’s monograph is entitled “Infectious metabolic and related diseases.” Particular attention is attributed to the anterograde and retrograde impairments observed in herpes simplex encephalitis, which is most pertinent given that patients with this pr~ominantly bitemporal disease present relatively little cognitive deterioration. Kapur’s review lead him to conclude that short-term memory, procedural learning and implicit memory are also normal in these patients. The chapter also reviews studies of metabolic diseases, especially hypoxia, which may result in memory deficits accompanied by variable degrees of cognitive impairments. Chapter 8 The next nosological heading is “Toxic and deficiency states.” It is primarily concerned with investigations of the effects of chronic alcoholism, Korsakoffs syndrome included. This is an interesting chapter which raises and discusses a number of Fundamental issues. As is evidenced from Kapur’s description, the symptom complex comprised of anterograde amnesia, confabulations, and retrograde amnesia with relatively intact procedural learning and implicit memory characterizes Korsakoff patients. Contradictory data have been reported regarding short-term memory in Korsakoff s syndrome : for instance Butters, Cermak and their colleagues did and Kopelman did not find Brown-Peterson procedure anomalies within their respective groups of Korsakoff patients; the reason for this contradiction has been widely discussed and. as is reported by Kapur, it is now generally recognized that it arose

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from differences in methodology and/or population characteristics. Resorting to a wide range of tasks, it has been shown, on the other hand, that the memory impairments of non-Korsakovian patients with a history of chronic alcohol abuse are less severe than those observed in full-blown Korsakoff’s syndrome and questions remain as to whether their memory deficits are to be placed along the same continuum. Kapur points out that patients with a history of chronic alcohol abuse differ from Korsakoff patients on a number of respects: they do not exhibit an increased sensitivity to proactive interference and produce less false positive and intrusion errors. Kapur provides no discussion as to whether these should be considered sounded evidence of a qualitative difference or whether these can be accounted for by the deficits being more severe in Korsakovian than in non-Korsakovian patients. Chapter 9 As indicated by its title (“Epilepsy”), Kapur’s penultimate chapter reviews studies of the inter-ictal and peri-ictal memory deficits of epileptic patients. A majority of studies have documented the existence of some degree of memory impairment in such patients. The author insists on the higher incidence of memory disorders in temporal as opposed to non-temporal epilepsies, and he underlines that such disorders are, up to a point. task-specific (i.e. greater visuo-spatial learning deficits in right-hemisphere epilepsies vs greater verbal learning deficits in left-hemisphere ones). Chapter 10 The last chapter of Kapur’s book is entitled “Ablation/disconnection of cerebral tissue. ” The author offers at this point a most interesting introduction to the issue of ablation studies in relation to memory functions. According to him, subjects with resections of various regions of the brain represent a unique target population given their characteristics as opposed to patients with natural lesions: the latter are seldom restricted to a given anatomofunctional territory and premorbid assessment is a rarity. Obvious limitations are nevertheless inherent to investigations of the brain-behaviour relations fonded on ablations and Kapur’s opinions in this respect are clearly stated and most pertinent: he discusses for instance the impact of the preoperative cognitive status of patients with a neurological illness and also the possibility of interactions between a number of factors (e.g. subclinical lesions, drug therapies, test-retest effects) and pre-operative performance; and he points out that neurosurgical resections are seldom submitted to post-mortem verification. Given that surgeons usually do not operate on normal brains, one might wish to resort to a more classical argument: again if one is interested in brain/behaviour relationships, to what extent can one generalize - to normal function - conclusions that have been drawn from studies of subjects NPL 5/4-E

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with a long-standing neurological illness, sometimes present from childhood (such as is often the case in surgery for epilepsy). As pointed out by Marcel (1990) in a different context, a similar limitation might be extended to the investigation of human cognitive architecture since these might also be the object of a reorganization as the result of an early brain lesion. Thus, we certainly agree that researchers proposing models based on such data need to keep these fundamental points in mind. In spite of these limitations, ablation studies have provided valuable informations on the cerebral organization of memory functions. The most relevant pieces of evidence are those which have arisen from selective cortica1 resections undergone for the relief of epilepsy. which have indicated the role of medial st~ctu~s such as the hip~~pus in memory processing, es~biish~ the necessity of bilateral involvement in the genesis of the amnesic syndrome, and highlighted the material specificity of memory losses after right vs left temporal lobe lesions. Kapur also discusses more recent studies focused on frontal lobe ablations : subjects submitted to surgery of this sort are said to show selective memory deficits characterized by an increased sensibility to interference and by an impairment in the temporal organization of events. Each of the nine chapters related to a given etiology includes a section the goal of which is to delineate the memory deficits which Kapur considers to be characteristic of this etiology to the exclusion of others, sometimes independently of lesion sites and sometimes not. This is obviously a worthy enterprise, although a very complex one as well. The identi~cation of etioiogi~aiiy distinctive features may, in our opinion, be motivated both by clinical - Kapur’s main option as indicated by the title of his book - and by theoretical goals, the latter aimed at problems pertaining to the cognitive and/or the neurological sciences. One obvious purpose has to do with diagnosis. Given the daily preoccupations of those involved in clinical neuropsychoiogy, one would for instance be interested in knowing whether the pattern of memory deficits of patients with primary degenerative dementia can be distinguished from that inherent to normal aging, or again from that observed in severe depression. This would be typical of a clinically driven preoccupation but it does not exclude theoretical preoccupations; for instance, in the present case, one might wish to raise the question of the existence or not of a qualitative difference between the memos impai~ents observed in senescence as opposed to senility. On the other hand, distinctive features will also be sought by those researchers whose aim is to identify and describe particular neurophysiological memory systems. If Huntington’s disease, Parkinson’s disease and Aizheimer’s disease each disrupts a different physiological component among those subserving memory, it would for instance be of the greatest interest to know more about the characteristics of these subcomponents (see the work of Butters and his group, for example Butters et al. 1987). In that case, as in a few others where problems of diagnosis are relevant, the underlying goals for the identification of distinctive features are clear in Kapur’s monograph and the impression is that evidences

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are starting to emerge. Yet, the reader wonders at times if it is indeed feasible at this point - and from what point of view it would be systematically useful to detine distinctive features for each and all of the pathologies discussed in the book. Kapur’s monograph is thus parsed along the etiology dimension, an organization obviously meant to be useful to the clinician by allowing rapid reference to the chapter pertaining to a specific pathology encountered in the course of her or his daily work. However, this choice was bound to lead the author to a number of. assumptions concerning the structure of knowledge and its relationship to that of the human brain. In fact, the monograph implicitly postulates (a) that memory disorders clearly differ according to etiology, and (b) that patients with a given pathology are homogeneous as to their memory deficits. These two postulates would certainly not meet agreement among all students of the neuropsychology of memory (Neary er al. 1986; Shallice 1988). Moreover, it becomes obvious, as one reads Kapur’s book, that neither stems from the empirical data being taken into account in the same context. Since each of its chapters is meant to be complete in itself, another consequence of the book’s organization is that reading it as a whole soon becomes fastidious in view of its redundancies. Perhaps the information would have been more easily assimilated had it been explicitly related to theoretical models of memory functioning, especially since. as pointed by the author himself, “many such models have been developed and tested in neurological populations. ” Had Kapur’s book focused on understanding the various memory disorders linked to particular pathologies as well as on diagnosis per se, it might have left more room for a productive interaction between theoretical and clinical preoccupations, which might in turn have provided clinicians with a still more useful tool, i.e. one targetted at permitting to devise rational rehabilitation procedures founded on thorough understanding - by reference to an explicit theoretical model of memory functions - of each patient’s specific disorder (Van Der Linden and Van Der Kaa 1989; Howard and Patterson 1989). As a matter of fact, the author does make a step in this direction when he encourages clinicians to develop their own instruments, which is certainly pertinent since, until recently, testing batteries and re-adaptation recipes have seldom been anchored on explicit theories of cognition. All of this being said, Kapur’s monograph is, on the whole, very informative in that it reviews a tremendous amount of researches and it is no doubt a book that shall be appreciated by clinicians and researchers. The author is obviously very well acquainted with both patients and the literature. He is aware of most of the methodological limits of the studies and techniques that he presents, and he is critical about them. Most importantly, he does make attempts at discussing a few important theoretical and methodological issues.

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NOTES 1. 2. 3.

Boursiere post-doctorale du Fonds de la recherche en Sante du Qu&ec. Professeur B la Facultt de medecine, Universite de Montreal. Researches at the Centre de recherche du Centre hospitalier C&e-des-neiges are funded by the Centre de recherche mt5dicale du Canada and by the Fond de la recherche en santt? du Quebec.

REFERENCES Baddeley, A 1986 Working Memory, New York: Oxford University Press. Baddeley, A., J. Harris, A. Sunderland, K. P. Watts and B. Wilson 1987 “Closed Head Injury and Memory,” in Neurobehavioral Recovery from Head Injury, R. V. S. Levin, J. Grafman and H. M. Eisenberg (eds), New York: Oxford University Press. Butters, N., D. P. Salmon, E. Granholm, W. Heindel and L. Lyon 1987 “Neuropsychological Differentiation of Amnesic and Dementing States,” in Cognitive Neurochemistry, S. M. Stahl, S. D. Iversen and E. C. Goodman (eds), Oxford: Oxford University Press. Caramazza. A. and M. McCloskey 1988 “The Case for Single-patient Studies,” Cognitive Neuropsychology 5. 517-28.

Ellis, A. W. and A. W. Young 1988 Human Cognitive Neuropsychology, East Sussex: Erlbaum. Howard. D. and K. Patterson 1989 “Models for Therapy,” in Cognitive Approaches in Neuropsychological Rehabilitation, X. Seron and G. Deloche (eds), East Sussex: Erlbaum. Kaszniak. A. W. 1986 “The Neuropsychology of Dementia*’ in Neuropsychological Assessment ofNeuropsychiatric Disorders, I. Grant and K. M. Adams (eds), Oxford: Oxford University Press. Lecours. A. R. and S. Belleville 1989 “Structures mutuelles du lexique et de la memoire,” Reeducation Orthophonique

27. 267 - 302.

Lussier, I., D. Malen fant, I. Peretz and S. Belleville 1990 “Caracttrisation des troubles de la memoire dans la demence de type Alzheimer.” in Syndromes dementiels: approche clinique et neuropsychologique, Paris: Masson.

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Marcel, A. J. 1990 “What Does it Mean to Ask Whether Cognitive Skills are Prerequisite for Learning to Read and Write? - A Response to Cossu and Marshall,” Cognitive Neuropsychology 7. 4 1 - 8. Morris, R. G. and M. D. Kopelman 1986 “The Memory Deficits in Alzheimer-type Dementia: A Review,‘* Quarterly Journal of Experimental Psychology 38. 77-97. Neary, D., J. S. Snowden, D. M. Bowen, N. R. Sims, D. M. A. Mann, J. S. Benton, B. Northen, P. 0. Yates and A. N. Davison 1986 “Neuropsychological Syndromes in Presenile Dementia due to Cerebral Atrophy, ” Journal of Neurology, Neurosurgery and Psychiatry 49. 163-74. Peretz. I., S. Belleville and S. Larochelle n.d. “Fractionnement de la mdmoire: Evidences a partir de l&ions corticales,” in Neuropsychologie de la m&wire humaine, M. Van der Linden and R. Bruyer (eds), Grenoble: Presses Universitaires de Grenobles (in press). Shallice. T. 1979 “Case-study Approach in Neuropsychological Research,” Journal of Clinical Neuropsychology 1. 183 - 2 11. 1988 From Neuropsychology to Mental Structure, Cambridge: Cambridge University Press. Valdois, S., Y. Joanette, A. Poissant, B. Ska and F. Dehaut 1990 “Heterogeneity in the Cognitive Profiles of Normal Elderly,” Journal of Clinical and Experimental Neuropsychology 12. 587 -5%. Van der Linden, M. and M.-A. Van der Kaa 1989 “Reorganization Therapy for Memory Impairments,” in Cognitive Approaches in Neuropsychological Rehabilitation, X. Seron and G. Deloche (eds), East Sussex: Erlbaum.