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Depression is characterized by distinct profiles of disturbance in ways autobiographical memories are represented, recalled, and maintained. We review four core domains of difficulty: systematic biases in favor of negative material; impoverished access and responses to positive memories; reduced access to the specific details of the personal past; and dysfunctional processes of rumination and avoidance around personal autobiographical material. These difficulties drive the onset and maintenance of depression; consequently, interventions targeted at these maladaptive processes have clinical potential. Memory therapeutics is the development of novel clinical techniques, translated from basic research, that target memory difficulties in those with emotional disorders. We discuss prototypical examples from this clinical domain including MEmory Specificity Training, positive memory elaboration, memory rescripting, and the method-of-loci (MoL).

Semantic memory encompasses knowledge of objects, facts and words. A number of brain regions are probably involved, but the left infero-lateral temporal lobe appears to play a key role. The separability of semantic memory from episodic (or autobiographical) memory is a focus of current debate. Impaired semantic memory is a common feature of Alzheimer's disease but is invariably overshadowed by a profound deficit in episodic memory. In semantic dementia, a rarer disorder associated with focal temporal-lobe atrophy, there is selective loss of semantic memory, characterized by preservation of superordinate knowledge of words, and objects, but loss of finer-grained information. This pattern can be interpreted as a degradation of features from a distributed network of semantic representations. Following Herpes simplex encephalitis, patients sometimes show disproportionate loss of knowledge for natural kinds (e.g. animals) with relative preservation of knowledge about artefacts, this may reflect differential damage to neural systems critical for perceptual as opposed to functional features, perceptual properties being more salient in knowledge about natural kinds.

Declarative memory is usually described as consisting of two systems: semantic and episodic memory. Between these two poles, however, may lie a third entity: personal semantics (PS). PS concerns knowledge of one's past. Although typically assumed to be an aspect of semantic memory, it is essentially absent from existing models of knowledge. Furthermore, like episodic memory (EM), PS is idiosyncratically personal (i.e., not culturally-shared). We show that, depending on how it is operationalized, the neural correlates of PS can look more similar to semantic memory, more similar to EM, or dissimilar to both. We consider three different perspectives to better integrate PS into existing models of declarative memory and suggest experimental strategies for disentangling PS from semantic and episodic memory.

Memory is prone to distortions that can have serious consequences in everyday life. Here we integrate emerging evidence that several types of memory distortions - imagination inflation, gist-based and associative memory errors, and post-event misinformation - reflect adaptive cognitive processes that contribute to the efficient functioning of memory, but produce distortions as a consequence of doing so. We consider recent cognitive and neuroimaging studies that link these distortions with adaptive processes, including simulation of future events, semantic and contextual encoding, creativity, and memory updating. We also discuss new evidence concerning factors that can influence the occurrence of memory distortions, such as sleep and retrieval conditions, as well as conceptual issues related to the development of an adaptive perspective.

A challenge for theories of episodic memory is to determine how we focus memory search on a set of recently learned items. Cognitive theories suggest that the recall of an item representation is driven by an internally maintained context representation that integrates incoming information with a long time-scale. Neural investigations have shown that recalling an item revives the pattern of brain activity present during its study. To link these neural and cognitive approaches, we propose a framework in which context is maintained and updated in prefrontal cortex, and is associated with item information through hippocampal projections. The proposed framework is broadly consistent with neurobiological studies of temporal integration and with studies of memory deficits in individuals with prefrontal damage.

It has recently been observed that the brain network supporting recall of episodic memories shares much in common with other cognitive functions such as episodic future thinking, navigation and theory of mind. It has been speculated that 'self-projection' is the key common process. However, in this Opinion article, we note that other functions (e.g. imagining fictitious experiences) not explicitly connected to either the self or a subjective sense of time, activate a similar brain network. Hence, we argue that the process of 'scene construction' is better able to account for the commonalities in the brain areas engaged by an extended range of disparate functions. In light of this, we re-evaluate our understanding of episodic memory, the processes underpinning it and other related cognitive functions.

Conflicting models persist over the nature of long-term memory. Crucial issues are whether episodic memory and recognition memory reflect the same underlying processes, and the extent to which various brain structures work as a single unit to support these processes. New findings that have resulted from improved resolution of functional brain imaging, together with recent studies of amnesia and developments in animal testing, reinforce the view that recognition memory comprises at least two independent processes: one recollective and the other using familiarity detection. Only recollective recognition appears to depend on episodic memory. Attempts to map brain areas supporting these two putative components of recognition memory indicate that they depend on separate, but interlinked, structures.

Episodic Memory: New Directions in Researchedited by Alan Baddeley, Martin Conway and John Aggleton,Oxford University Press, 2002. £19.99/$35.00 (pbk) (294 pages) ISBN 0 19 850880 8This is an excellent compilation of chapters written by leading researchers interested in episodic memory. Although not every leader in the field is represented, those that are comprise an impressive list. Thus there is achieved a coverage that manages to be both broad and deep, dealing with research and ideas at the forefront of research in this area. Correspondingly, there are chapters likely to be of value to research specialists, to those interested more generally in research into memory, and to students. The book as a whole represents a major contribution to the debate concerning the fractionation of memory and the definition of specific of memory attributes at the psychological and systems levels of analysis. Indeed, perhaps its greatest merit is in collecting together such a range of varied contributions and thereby facilitating comparison between the different views and approaches.The areas covered include primarily studies of memory in normal and amnesic humans (being the main focus of twelve chapters), but there is also work on animals as it may (or may not) be related to episodic memory (three chapters). Two key themes running through the book are what precisely is ‘episodic memory’ and, consequentially, can it be studied in species other than our own. Although there is general agreement that an episodic memory is of a particular occurrence in a particular place at a particular time – that is, it comprises information concerning ‘what’, ‘where’ and ‘when’ – the necessity for the element of ‘mental time-travel’, or being able consciously to image mentally that one's self was present at the original episode (having autonoetic consciousness for the episode) is the subject of much discussion. However, there is agreement among the contributions of those engaged in studies of animals that, at present, animal memory can at best be described as ‘episodic-like’.The issues are set in perspective by an opening chapter containing a brief historical overview and scene-setting by Alan Baddeley. This chapter establishes an excellent standard that is remarkably sustained in the other contributions: it is a pleasure to read a collection of fifteen chapters whose quality is so consistently high. Appropriately, the last chapter, though it certainly will not be the final word on this subject, is written by the originator of the term ‘episodic memory’, Endel Tulving. He provides a critical review of the preceding chapters from his perspective, before stating how his own views on the subject have developed to their present formulation. In between, there are chapters on a wide variety of different topics. Thus John Gardiner discusses dissociations between semantic and episodic memory established by the ‘remember–know’ (or, in relation to this debate, the ‘autonoetic–noetic’ consciousness) paradigm, and the impairment of episodic memory found in patients with Asperger's syndrome. Defining the boundaries of and possible subdivisions within episodic memory is a theme continued by Andrew Yonelinas's description of evidence for the separation of recognition memory into familiarity and recollective components, and Martin Conway's discussion of the relation between episodic memory and autobiographical memory. What studies of false memory have to teach us is discussed in a chapter by Daniel Schacter and Chad Dodson. Although also providing input to other chapters, discussions of the contributions of studies of different types of amnesic patients are the chief focus of contributions by Michael Kopelman and Narinder Kapur concerning retrograde amnesia, John Hodges and Kim Graham reviewing insights from semantic dementia patients, and Faraneh Vargha-Kardem, David Gadian and Mortimer Mishkin on what can be deduced from studies of patients with developmental amnesia. Each of these chapters provides a valuable and succinct review of the past and current work of these researchers in these fields. A wide-ranging chapter by Andrew Mayes and Neil Roberts, considers the evidence for different brain structures’ involvement in different memory processes. Although imaging studies receive mention by a number of contributors, the only chapter devoted to imaging is the review by Eleanor Maguire of reports of brain activations relating to autobiographical event memory. In a chapter by Neil Burgess, Suzanna Becker, John King and John O'Keefe, a model of memory for events and their spatial context is outlined together with the results of related imaging studies.The contribution of animal studies and how spatial memory, event memory or episodic-like memory in animals might relate to human episodic memory is the focus of chapters by Richard Morris, John Aggleton and John Pearce, and Nicky Clayton, D Griffiths, N Emery and Tony Dickenson. Each of these chapters provides strong evidence and arguments in favour of parallelisms between memory in humans and other species. For example, Morris points out parallelisms related to brain structure and what is known of possible underlying learning mechanisms at the synaptic level. Aggleton and Pearce emphasize the relationship between brain structures involved in spatial memory and those involved in episodic memory, in the light of the associations between spatial memory, structural discrimination learning and the ‘where’ component of episodic memory. Clayton and co-authors give a comprehensive review of their studies of memory in birds whose results are widely agreed to provide evidence for the most episodic-like memory yet demonstrated in a non-human species.In conclusion, this book provides an important summary of many results and current views relating to episodic memory. In so doing, it is likely to provide an important stimulus to future work. It greatly aids the process of bringing into focus issues concerning the definition and properties of episodic memory, and of its neural substrates. Moreover, it clearly sets out a challenge to the inventiveness of researchers to try to establish just how like our episodic memory any memory in other animals might be.

From Conditioning to Conscious Recollection: Memory Systems of the Brainby Howard Eichenbaum and Neal J. Cohen, Oxford Psychology Series, OUP, 2001. £47.50 (ix + 583 pages)ISBN 0 19 508590 6This text sets out on an admirable task of describing the extensive literature relating to the study of human memory. Eichenbaum and Cohen, both well-established experts in the field, have compiled a large collection of data and research from humans and non-humans on the neurobiology and neuropsychology of memory functioning. The central tenet is the concept of multiple memory systems and the rejection of memories as ‘items’ stored in specific brain regions. The authors have undoubtedly produced a comprehensive and detailed account of the neurobiology of memory, and raise several interesting ideas and reconsiderations of our understanding of memory. In my view, the greatest benefit in this text lies in its completeness, and the extensiveness of data presented and available for consideration.The book is laid out system-by-system but frequently attempts to reconcile these systems with neuroanatomical structures and inter-related circuits. This was an admirable and noble undertaking. Occasionally, however, the important message of considering memory as multiple (but inter-related) systems has been somewhat lost in the density of data presented. The text is also top heavy with neurobiological data and non-human evidence. Considerably less is given to the extensive data from neuropsychology, in particular cognitive neuropsychology. The authors do provide evidence from the many studies of H.M. and an update on this fascinating and landmark case was a welcome inclusion. However, there is more to memory loss than H.M. (and the hippocampus) and unfortunately this was not always evident.Stylistically, the text was clear but densely packed and I must confess to finding the frequent and regular repetitions and introductions to each section a distraction eventually. The introduction is detailed and provides an interesting and scholarly review of the history of memory research. One intriguing insight covers the concept of memory transfer through cannibalism. Donor worms were trained on a particular task (avoiding shock) and were then fed to ‘naive subjects’ (presumably other worms), which were then thought to show a preference for the avoided direction. This spawned a huge search for ‘memory molecules’, although extension of the methodology to humans was surprisingly slow! Nevertheless, despite espousing the concept of multiple interconnected systems one can't help but feel that there is a continuing search for an elusive memory molecule – albeit now through neuroimaging and sophisticated laboratory experiments.Eichenbaum and Cohen continue to make many of our regularly used metaphors (such as memory as a warehouse, cellular event or switchboard) explicit and clearly redundant. They move towards a conceptualization of memory as a higher-order property of brain function in a similar vein to conceptualizations of the mind–brain debate [1xSearle, J.R. See all References][1]. This need for a clear and accepted nomenclature has recently been taken up by others [2xConcepts of memory. Tulving, E. : 33–45See all References][2], particularly with regard to the clarification of memory as system, event, structure or process. This text clearly and unequivocally dispels the myth of memory as a specific entity, but although we are moving towards a description of the properties of such systems, the enormity of the task ensures that we are a long way from a clear understanding of these systems, their properties and their interconnections. A conceptualization of the hippocampus, amygdala and neostriatal memory systems associated with particular functions is accepted and the need to view these as independent but parallel systems is similarly well developed. Yet I particularly liked the manner in which the authors redefine the role of these structures as nodal points in an integrated system.Towards the end of the book neuropsychological evidence is eventually considered in support of more specialized memory systems. The data on motor learning and habit memory is interesting but little time is spent on the contribution from studies of memory impairments associated with conditions such as Huntington's disease (HD) and Parkinson's disease. A small note of such difficulties is made with reference to the role of the striatum in sequencing. Models of multiple cortico–striatal systems are well developed and may well have enhanced and supported the authors’ current position on multiple systems [3xThe functional anatomy of disorders of the basal ganglia. Albin, R.L et al. Trends Neurosci. 1995; 18: 63–64Abstract | Full Text PDF | PubMed | Scopus (228)See all References][3].Importantly, the concepts of forgetting and its relationship with temporal memory is addressed and excellent data on source memory and temporal loss are presented. It is suggested that the observed temporal gradient in retrograde amnesia relates both to hippocampal damage and frontal lobe damage. But limited data are presented for conditions such as Dementia of the Alzheimer's Type, in which temporal gradients and memory loss are intricately linked, and HD, where research data suggests severe loss without a temporal gradient. The suggestion of damage outside the medial temporal lobes (MTL) is proposed (that frontal-lobe damage results in the loss of source memory). This might be so, and is plausible in HD as there are disruptions in numerous frontal striatal connections [4xMovement disorders and frontal-subcortical circuits. Lichter, D.G. See all References][4] but the general lack of MTL damage in early HD raises interesting questions for this theory.In summary, this is a scholarly if ambitious text. The authors have amassed an extensive collection of data in order to support the concept of multiple memory systems, which sits comfortably with the direction of current memory research. In spite of some omissions in specific areas (and after all, in a field such as this, that there are so few is praiseworthy) From Conditioning to Conscious Recollection is an excellent review of past and current memory research, and will undoubtedly be an excellent resource to many cognitive neuroscientists.

A highly adaptive aspect of human memory is the enhancement of explicit, consciously accessible memory for emotional stimuli. Recent findings from neuroimaging, neuropsychological, drug and neural stimulation studies indicate that emotional stimuli engage specific cognitive and neural mechanisms that enhance explicit memory. Emotional arousal influences memory via factors that act during memory encoding (attention and elaboration) and factors that modulate memory consolidation. Across studies, the amygdala has been consistently implicated as playing a key role in enhancing explicit memory for both pleasant and unpleasant emotional stimuli through modulation of encoding and consolidation processes.

The question of whether episodic memory, the ability to recall unique, personal experiences, is restricted to humans is a matter of current controversy. Recent work on food-storing jays suggests that several features of episodic memory may not be as exclusive to humans as previously thought. In this review we outline the critical features of episodic memory in humans, its relationship to declarative memory, and recent results revealing that jays can learn to perform a task that depends on certain features of episodic memory and can thus be considered 'episodic-like'. Finally, we compare this avian performance with a contemporary definition of human episodic memory and consider the implications for studies of hippocampal function and animal cognition.

Harvard University Press (1998). £21.95 (viii + 244 pages)ISBN 0 674 58205 5As its title suggests, this book is concerned with memories for important personal experiences or momentous events. David Pillemer argues that single events can change the course of a person’s life. The strongly positive reviews adorning the back of the dust jacket make much of this argument. Several comments about it are warranted: first, it would be hard to find anyone who claimed not to believe that striking individual experiences can alter the course of their life and that this would not happen if they did not remember the experiences frequently on later occasions. Second, the book is well written and the examples of influential experiences in people’s lives make for good reading. For example, we learn that Endel Tulving was struck by the comment of a colleague about the tenure prospects of a young scholar that ‘he had not written his book yet’. Although not aimed at him, Tulving gave personal significance to the remark so that it was transformed into the personal directive ‘I must write my book’. Presumably, we owe ‘Elements of Episodic Memory’ to Tulving’s frequently remembering this particular occasion and its significance for him. Or do we? This relates to the third comment, because although we all believe that single events can have clearcut effects on our lives, it is very much harder to find convincing evidence about the extent to which they do so, and it is far from obvious that Pillemer has provided such proof. The writing of Tulving’s book was clearly dependent on many things, only one of which might have been this particular memory about a colleague’s remark.Pillemer organizes his discussion of personal-event memory around five themes: (1) the role that memories play rather than whether or not they are accurate; (2) how the ability to create narratives related to personal experiences and to use these in social interactions develops in childhood; (3) conceptualizing personal memory at multiple levels in order to indicate the complexity of the interconnections involved; (4) how group and individual factors such as culture, gender and personality influence the use of personal memory; and (5) a central focus on the impact on life of memory for events that occurred in one moment of time. This central emphasis is contrasted with what Pillemer regards as the usual emphasis on cognitive and memory processes: that they are summaries of repeated happenings, as is the case with semantic memory and processing.Highlighting the book throughout are the examples of emotional personal memories. Not surprisingly, these memories contain very strong imagery, but the book is concerned with how we become very skilled at translating these images into narrative form. Although I did not think that this book adds anything to our knowledge of how episodic memory works, the discussion of the narrative-imagery issue in relation to infantile amnesia was interesting. Thus, as the study of Perris et al. (discussed in Chapter 4) makes clear, children exposed to an auditory localization experiment at just over six months of age show behavioural evidence of memory of the experience two years later, thus, long-term memory of some kind must be present even before the age of three. The relative importance of the emergence of the ability to translate imagery memories into narratives in infantile amnesia might not, however, be as great as Pillemer implies. I was also worried by the apparent equation of imagistic memory with implicit memory that seems to be made (p. 103). This is surely wrong, because we know when images are memories just as much as we know when the narratives we generate are memories. In other words, both are typically explicit or declarative memory.The need to stress the importance of episodic memory relative to abstracted semantic memory might also have led to misleading claims in places. For example, the experiment of Conway and his colleagues (discussed on p. 15) is cited as support for the idea that factual memory might, at least initially, be based on remembering specific personal experiences. This conclusion does not follow from the experiment: memory for contextual detail may well accompany the ability to recall a fact, but that does not mean that such episodic memory is necessary for the factual memory.Overall, my impression is that this is a readable book which deals with aspects of memory that are of human interest rather than those that contribute much to understanding the mechanisms underlying episodic memory. Nevertheless, it contains information that will be useful for people primarily concerned with these mechanisms. I found particularly interesting the discussion in the final chapter about individual differences in the extent to which people recall specific incidents when asked to do so. Surprisingly, some people are very unlikely to do this even when pressed, preferring instead to give general accounts. For example, asked about an experience from school, they might refer to remembering how crowded things were and how everything seemed very chaotic early in the school term rather than describing an experience in a particular lesson. This individual variability in retrieval of discrete personal episodes should sound a note of caution in interpreting reports that particular amnesic patients sometimes fail to recall any personal incidents, although they can recall general things as in the school example. How can we be sure that these patients would not have been unlikely to recall specific episodes when asked to do so even before they suffered the brain damage that triggered their amnesia?In summary, Momentous Events, Vivid Memories is a well-written book that will be of most interest to those wanting to learn more about the impact of emotional, and sometimes traumatic, memories on the direction of people’s lives. It might also provide some useful insights to those working in the field of memory mechanisms.