Cases of Amnesia

Contributions to Understanding Memory and the Brain

Sarah E. MacPherson, Sergio Della Sala, Sarah E. MacPherson, Sergio Della Sala

• Publisher: Routledge
• Year: 2019
• Print ISBN: 9781138545557
• eBook ISBN: 9780429657047
• Topic: Psicologia
• Subtopic: Psicologia clinica

In all cognitive domains, neuropsychological research has advanced through the study of individual patients, and detailed observations and descriptions of their cases have been the backbone of medical and scientific reports for centuries. Cases of Amnesia describes some of the most important single case studies in the history of memory, as well as new case studies of amnesic patients. It highlights the major contribution they make to our understanding of human memory and neuropsychology.

Written by world-leading researchers and considering the latest theory and techniques in the field, each case study provides a description of the patient's history, how their memory was assessed and what conclusions can be made in relation to cognitive models of memory.

Edited by Sarah E. MacPherson and Sergio Della Sala, Cases of Amnesia is a must read for researchers and clinicians in neuropsychology, cognitive psychology and cognitive neuroscience.

1
The Single Case Study of Memory

Tim Shallice

Introduction

This book is on a very important topic for scientific neuropsychology. It concerns the in-depth study of individual neurological patients with striking disorders in some aspect of the field of memory. Of all the areas of psychology, it is the area of memory, where in the last hundred years, the description of a surprising disorder in a single patient following a neurological intervention or disease that has had the most impact. Memory is a field where most of the greatest scientific advances from neuropsychological investigations have come from studies of a single patient, or less frequently, a few very similar patients, each treated as individuals. The seemingly more standard method of contrasting the average performance of large groups of patients has made much less of a splash. Interestingly, this is not true of all areas of psychology; executive functions are, for instance, a counterexample. However, for a variety of mainly bad reasons, the single case approach is currently being increasingly ignored across the board in favour of the seemingly more scientific, but actually less informative, study of the average performance of groups of patients. This book describes some of the most important single case studies in the history of memory. It shows the efficacy of the approach.

Descriptions of individual patients with selective disorders were a standard procedure in the late 19th century until the 1920s, and this was to become neuropsychological research. The approach reached its acme in the work of the diagram makers in language towards the end of the 19th century. In memory too, doctors working with neurological patients at that time were well aware of the existence of amnesia (i.e., the loss of the ability to retrieve information about one’s personal past) (see, e.g., Chapter 6 this volume). Indeed, clinicians, such as Korsakoff, and in particular von Bekterew, associated amnesia with lesions to the diencephalon and even the hippocampus (Moscovitch, 2012).

However, in such work, descriptions of the cognitive state and behaviour of patients tended to be rather imprecise, non-quantitative and primarily the clinical interpretation of the investigator. So, in the 1920s and ’30s, this method began to be seen as being insufficiently scientific. Aphasia researchers, such as Head (1926) and Weisenburg and McBride (1935), as well as Rylander (1939) who studied disorders of executive functions, introduced a more systematic and quantitative approach. This had two aspects. First, and very valuably, tests began to be standardised, or at least applied systematically, and with results reported quantitatively. Second, and less clearly beneficial, the performance of a series of patients selected using fairly wide criteria was reported, not just individual cases showing striking dissociations. Scientific neuropsychology was seen as embodying both aspects.

Human neuropsychological research at the time, however, had little impact on the scientific study of mental processes. This would, in any case, have been particularly difficult, especially in the field of memory. At a theoretical level, the doctrine of mass action (Lashley, 1929) was dominant. It viewed the effects of damage to the association cortex (i.e., the entire cortex except that devoted to perceptual or motor processing), as only a question of the amount of tissue loss; the specific location of the damage was held to be unimportant.

Milner on Selective Amnesia

Neglect of single-patient data and adherence to mass action ended dramatically following the publication of a number of papers in the late 1950s, in particular one reporting the memory disorder of HM (see Chapter 2 this volume) that occurred following bilateral medial temporal surgery aimed to reduce his epilepsy (Scoville & Milner, 1957). After his surgery, HM had a very severe amnesia, which meant he had virtually no conscious memory of what happened even minutes before. So, for example, the same joke could be told many times in an hour as he would not remember having told it before.

The dramatic change in impact resulting from the papers describing HM occurred for seven main reasons, six intellectual and one social:

1. HM’s problems were restricted to memory; intelligence, for instance, was unaffected.
2. HM’s difficulties were described clinically but also, critically, they were demonstrated quantitatively using the Wechsler Memory Scale and the Wechsler Adult Intelligence Scale.
3. The disorder was extremely severe. It was far from being a marginal effect.
4. Patient HM had been relatively normal as far as memory was concerned pre-surgically; the memory problems were clearly caused by the removal of a particular region of brain.
5. As far as the brain itself was concerned, the fact that the damage occurred as a result of neurosurgery meant that most unusually for neurological patients at that time, information about the localisation of damage was available prior to post-mortem. Moreover, the lesions were relatively localised, being restricted to one part of the brain bilaterally; they were not diffuse. In other words, Lashley was wrong.
6. Similar memory problems were found in six other patients, whose difficulties were studied individually, not as a group. These six were, however, psychotic prior to their operations, as the neurosurgeon Scoville was a great proponent of prefrontal leucotomy (see Dittrich, 2016). Yet, similar, if somewhat milder, effects had been found by Milner and Penfield (1955) in two patients who underwent left medial temporal removal due to more conventional neurosurgery. Such memory deficits were unusual for unilateral patients, but were compatible with the findings on HM, if there had actually been damage in the other hemisphere which could not be detected given the methods available at the time. There was also a bilateral neurosurgical patient reported by Terzian and Dalle Ore (1955) who had similar memory problems to HM, together with features of the so-called Klüver-Bucy complex. This meant that HM was not a completely isolated unusual case.
7. Finally, from the important point of view of impact, the neurosurgeons Scoville and Penfield were very well known to the North American neuroscience community.

Milner followed up her original findings, by showing that there were aspects of memory which were still intact in HM (Milner, Corkin & Teuber, 1968). These, for instance, included his ability to learn procedural memory skills, such as mirror drawing. Warrington and Weiskrantz (1968), using a mixed individual case/group design, then found analogous preservation of perceptual learning; they averaged the performance of six patients, all of whom had a relatively pure amnesic syndrome.

An additional factor was soon to be added. Milner’s studies do not appear to have been greatly influenced by the beginnings of cognitive psychology, which was occurring at much the same time. However, that was soon to change. Performance on another memory task found to be intact in HM was digit span, in which participants must immediately repeat back a string of digits presented at a rate of one per second. Similar preservation of span was found by Drachman and Arbit (1966) in five patients with severe amnesia following bilateral hippocampal removals. They interpreted this pattern of intact span in their amnesic patients in terms of preservation of short-term memory with impairment of long-term memory, a theoretical contrast which was being much investigated in normal subjects by cognitive psychologists at the time (e.g., Waugh & Norman, 1965; Glanzer & Cunitz, 1966).

Short-Term Memory

This link between cognitive psychology and neuropsychology led to experimental memory paradigms developed by cognitive psychologists being applied to the study of patients. Take the free recall paradigm developed by experimental psychologists in the 1950s (e.g., Deese & Kaufman, 1957). Participants are presented with a list of unrelated words at a fixed rate and have to recall as many words as they can at the end of the list in any order. The probability of an item being recalled is very dependent on the position in the list the word is presented. Moreover, this dependence has a very characteristic form. The first (primacy) and the last (recency) few items are better remembered than the items in the flat middle part of the so-called serial position curve. In addition, the length of the primacy and recency parts of the curve are independent of the overall length of the list (Murdock, 1962). However, other variables, such as rate of presentation or whether interfering material is presented before the recall attempt, lead to very different effects on the primacy and middle parts of the curve compared with the recency part. Glanzer and Cunitz (1966), who discovered these effects, argued that the items retrieved in the primacy and middle components of the serial position curve are held in long-term memory. By contrast, they maintained that items retrieved in the recency part of the curve were being held in short-term memory too.

When the free recall paradigm was used by Baddeley and Warrington (1970) with a small group of relatively pure amnesic patients using a mixed individual case/group design, it was found that their performance was essentially normal in the recency part of the curve. In contrast, performance on the middle part of the curve was completely at floor and greatly reduced on the primacy part. This is exactly what one would expect if one combined Glanzer and Cunitz’s account of the free recall task with Drachman and Arbit’s (1966) position that short-term memory was preserved in amnesia.

This perspective was supported by the discovery of patients with a second sort of memory problem, namely a specific difficulty in auditory-verbal short-term memory (see also Chapter 13 this volume). Warrington and Shallice (1969) described a patient, KF, suffering from a left temporo-parietal head injury who had a digit span of only 2.3. Words could be perceived normally at the one-per-second digit span presentation rate, and digit naming could be replaced by pointing to written digits without any improvement in span, suggesting that spoken production was not the problem. Moreover, when carrying out the free recall task, patient KF performed in an opposite fashion to Baddeley and Warrington’s amnesics. Recency was restricted to a single item, instead of the normal five or so. Yet, the primacy and middle part of the curve were relatively intact (Shallice & Warrington, 1970).

Since the description of KF’s short-term memory problem, about 20 similar cases have been described in the literature (see Vallar & Shallice, 1990 for the earlier ones). However, the syndrome is subtler clinically than the amnesic syndrome. As a result, like virtually all new forms of memory impairment described since HM, there have been critics of the claim that a new functional syndrome has been isolated. For instance, Buchsbaum and D’Esposito (2008, p. 773) argued, “The sheer rarity of the STM patient, for there are no more than 10–15 cases reported in the literature, might indicate that there is something out of the ordinary in the underlying neurobiology of these particular individuals”. In fact, we do not know how rare the syndrome is, and indeed most patients with the classic clinical syndrome of conduction aphasia have short-term memory problems (Bartha & Benke, 2003; Gvion & Friedmann, 2012). Yet, they are not “pure” short-term memory cases; they have other problems too. I will return to this issue later.

The short-term memory patients were some of the main sources of evidence used by Baddeley and Hitch (1974) to support their model of working memory, which has become one of the most highly quoted in the area. In later versions of the model (e.g., Baddeley, 1986), the behaviour of these patients corresponds to an impairment of the phonological input buffer. Given the idea of a buffer as having two characteristics—the holding of information in the short term only and a dedicated procedure for retrieving that information—the idea of selective damage to buffers soon became productive. De Renzi and Nichelli (1975) briefly described two right hemisphere patients with scores on the non-verbal Corsi spatial scan test of 2.5, well below the normal range of 7. Both patients had perfect scores on a copy drawing test. Neither patient had neglect or any difficulty on a series of spatial perception tests. The problem would appear to be at the level of the visuo-spatial sketchpad component of the Baddeley-Hitch model (see also patients described by Farah, Levine & Calvanio, 1988 and Hanley, Young & Pearson, 1991). In contrast, Kinsbourne and Warrington (1962) have described four left hemisphere patients with difficulties reporting more than one visual item when more than one item is presented (see also Warrington & Rabin, 1971; Warrington & Shallice, 1980; see also Chapter 10).

Buffers are not only necessary parts of perceptual systems. They are also required in certain sorts of action systems. In support of this claim, Caramazza, Miceli and Villa (1986) and Caramazza, Miceli, Villa and Romani (1987) have described patients whose impairments correspond to damage to the phonological output buffer and graphemic output buffer, respectively, and these findings have been well replicated across other patients (see Shallice & Cooper, 2011, sections 7.5, 7.6 and 7.7).

Semantic Memory

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Table of contents

• Cover
• Half Title
• Series
• Title
• Copyright
• Dedication
• Contents
• Preface
• Acknowledgements
• List of Contributors
• 1 The Single Case Study of Memory
• 2 The Earthquake that Reshaped the Intellectual Landscape of Memory, Mind and Brain: Case HM
• 3 The Case of YR: Selective Bilateral Hippocampal Lesions Can Have Quite Different Effects on Item Recognition, Associative Recognition and Recall
• 4 Amnesic Patient VC: What Have We Learnt From Him?
• 5 What Did Amnesic Actor AB Teach Us About Learning His Lines?
• 6 Cases of Hippocampal Memory Loss: Dr Z, the Engineer and the Glove Cutter
• 7 Persistent Déjà Vu, Recollective Confabulation and the Case of Patient AKP
• 8 Case KC (Kent Cochrane) and His Contributions to Research and Theory on Memory and Related, Non-Memory Functions
• 9 Right is Right for Episodic Memories in Two Contrasting Case Studies, CH and JR: Focal Retrograde Amnesia and Public Semantic Amnesia
• 10 Sensory-Specific Visual Amnesia (Cases 1 and 2): An Acquired Visual-Limbic Disconnection Syndrome
• 11 ‘Yes, I Remember’—Apparent Consolidation Under Conditions of Minimal Sensory Input in a Case of Severe Anterograde Amnesia: Case PB
• 12 VA: A Case Report of Transient Epileptic Amnesia
• 13 A “Purest” Impairment of Verbal Short-Term Memory. The Case of PV and the Phonological Short-Term Input Store
• 14 Semantic Short-Term Memory and its Role in Sentence Processing and Long-Term Memory: Evidence From Cases AB and ML
• 15 Interrelationship Between Semantic Memory and Personal Experience: Evidence From Semantic Dementia Patients KE and WM
• 16 Iris Murdoch: Days Without Writing
• 17 The Wealth of Evidence From Brain Lesions Affecting Memory: How Should We Use It?
• 18 Biases and Concerns With the Single Case Approach in the Neuropsychology of Memory
• 19 The Case for Single Case Studies in Memory Research
• 20 Comments on the Single Case Approach to the Study of Memory and Other Domains of Cognition
• Index