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[Word Count: 1689]Copyright © 1997 Traumatology ForumThe revolution started slowly. For centuries, most philosophers and psychologists regarded memory as a unitary system. A lthough some concerned with animal and human learning and memory advanced ideas regarding multiple systems (e.g., Tolman, 1948), their hypotheses were not initially influential within the field (see Schacter & Tulving, 1994). Only after reports of amnesic patients whose selective memory deficits could not be accounted for by single system theories (see, e.g., Milner, Corkin, & Teuber, 1968; Scoville & Milner, 1957; Warrington & Weiskrantz, 1968, 1974; Zola-Morgan, Squire, & Amaral, 1986) did it gradually become apparent that such theories were no longer tenable.
Psychologists thus began attempting to fit theory to data from the animal literature and from clinical patients (see, e.g., Cohen & Squire, 1980; Graf & Schacter, 1985; Jacobs & Nadel, 1985, 1997; Metcalfe & Jacobs, in press; Nadel, 1992, 1994; Nadel & O'Keefe, 1974; O'Keefe & Nadel, 1978; Squire, 1992; Tulving, 1972). This theoretical work has spurred enormous advances in memory research over the pa st two decades. A vast body of empirical data now supports the existence of multiple memory systems. Specifically, the data suggest that different brain regions store different parts of past experiences, and that we construct a whole memory from these different parts (see Schacter & Tulving, 1994).
In Searching For Memory: The Brain, The Mind, and The Past, Harvard professor of psychology Daniel L. Schacter summarizes twenty years of cognitive, behavio ral, neurological, and physiological memory research. Despite lacking an integrative theoretical s statement to frame that research, the author nonetheless consistently presents evidence for the existence of multiple memory systems. Using memory's "fr agile power" (p. 7) as an organizing theme, Schacter's explication of multiple memory systems hypotheses argues against the notion that memory operates like a video recorder (i.e., that each of our experiences is stored away in our brain and is insta ntly accessible to us if we push the right buttons). This "fragile power" is more than an organizational tool for the author, however--according to Schacter, it is one of memory's defining qualities.
Illustrative of t his point is the book's unique use of memory-related artworks . These serve not only to engage the reader but also to demonstrate that people other than psychologists recognize both memory's fragility and its power.
The book's first three chapters examine ordinary memory processes from a multiple systems p erspective. Chapter 1 presents research suggesting that the subjective experience of remembering is a reconstruction, a complex process involving several distinct parts of the brain. Both current influences and preexisting, or stored, information abo ut the past affect this process. Chapter 2 focuses on encoding and retrieval, two basic memory processes. Schacter presents data suggesting three primary influences on the construction of a memory: fragments of our experiences that we retain at the encoding stage (called engrams), the way we encode those fragments, and the specific cues presented at the retrieval stage. Both the engram and the retrieval cue, then, contribute to the subjective sense of remembering di! scuss ed in the first chapter. Thus, the author suggests that "the retrieved memory is a temporary constellation of activity in several brain regions--a construction with many contributors" (p. 66). Chapter 3 examines recent research on forgetting, consoli dation of memories, and autobiographical knowledge of the past.
In the first three chapters, then, Schacter discusses the operation of ordinary memory processes (encoding, retrieval, consolidation, and forgetting) under ordinary conditions. The research presented in those chapters provides evidence for the hypothesis that memories are constructions involving the use of several different processes and multiple functionally and anatomically distinct systems. Those doing clinical interviews wo uld do well to be mindful of this and thus to maintain a neutral stance toward the memories produced by clients.
The power of memory derives largely from this finely-tuned network of automatic processes and systems. T! he fragility of this power is, however, illustrated by the ea se with which memory processes and systems may be upset, and memory distortions created, under both ordinary and extraordinary conditions. In subsequent chapters, Schacter discusses examples of such distortions and examines evidence bearing on their possible neural bases. Chapter 4 presents general research on distorted recollections. It appears that influences operating during encoding and within and upon the retrieval environment contribute to distorted recollections. Additionally, when sourc e information (i.e., details of the spatial and temporal context of an event) is missing, memories are susceptible to distortion. In Chapters 5 and 6, Schacter presents more detailed evidence for memory's brain substrates. To do this, he summarizes data from humans with amnesia and animals with brain lesions. The data converge to suggest that dam age to certain areas of the brain can lead to selective deficits for certain forms of memory while preserving other memory! and learning abilities. These data clearly support multiple systems hypotheses, and are important clinically because some clients have suffered minimal brain damage and consequent selective cognitive deficits.
In Chapters 7, 8, and 9, Schacter addr esses the impact of trauma on memory. Chapter 7 presents research on emotional memories, which may form from traumas that leave intense, and perhaps indelible, imprints on the brain. Here, he discusses characteristics of and possible neural processe s involved in flashbulb memories, flashbacks, and other trauma-related memories. Although Chapter 7 presents evidence that trauma is sometimes associated with clear, distinct memories, Chapter 8 presents evidence that trauma can also be associated wit h extensive amnesias. In his discussion of psychogenic amnesias, fugue states, and dissociative disorders, Schacter squarely faces the fact that researchers have yet to describe clearly the role of emotional trauma in crea! ting these memory distortions. It does appear, however, that damage to certain brain areas and stress-related hormonal changes in those brain structures is associated with amnesia for traumatic episodes. Crucially, single memory system theories have not resolved the paradox created by the data presented in Ch apters 7 and 8. In contrast, multiple systems hypotheses can account for the fact that trauma can sometimes lead to imprinted aspects of memories, while at other times can be associated with deficit s for other aspects. The clinical usefulness of thi s data is not yet apparent, because we do not yet know how to differentiate the various effects of trauma on memory.
Chapters 7 and 8 provide useful background for Schacter's examination of the recovered memories controversy in Chapter 9. From a moderate and scientific perspective, Schacter outlines his discussion around four distinct questions. First, can sexual abuse be forgotten? Second, can forgotten episodes of abuse be recovered? Third, can people develop! fal se recollections of traumas that never occurred? Fourth, are there reliable ways to distinguish veridical accounts from false recollections? Though the answers to these questions range from qualified affirmatives to definite negatives, Schacter is d etermined in his assertions that "we still have little good scientific evidence that bears directly on the key issues" (p. 277), and that, once such scientific evidence emerges, it may help to identify a middle ground between the bitter extremes that currently characterize this debate. From a clinical perspective, then, it is too soon to formulate a definite answer to the vexing questions surrounding recovered memories.
Chapter 10 examines memory in older adults, age-related memory deficits, and the tendency to increase the focus on the past as we age. Older adults' memory performance varies across situations and tasks. This is because brain structures related to source information and working memory, for i! nstance, show age-related decline. Older adults can overcome some age-related memory deficits, however, through elaborative encoding and guided retrieval, and most memory functions are preserved as people age. Clearly, this is positive news for clinicians treating older adult patients. Also, the data is again most parsimoniously interpreted by multiple memory systems theories.
The book's primary explicit theme, then, is that memory's power is the product of several functionally and neuroanatomically distinct systems efficiently working together. Us ing a multiple systems perspective, Schacter attempts to remove some of the mystery and unpredictability inherent in memory's unexpected failures and preservation under both ordinary and extraordinary circumstances. Paradoxically, though, the same ne twork of systems that produce memory's power can lead to its fragility. Processes within the systems may fail independently, leading, for example, to selective memory deficits and circumstances under which some parts of a s! eemi ngly coherent memory may be veridical while others are not.
Searching for Memory's primary implicit theme is that self-definition and memory are inextricably intertwined (see also Edelman, 1989). If the multiple memory systems hypot hesis is true, it necessarily influences the way we talk about the self and what we consider the self to be. That theme makes this book extraordinarily important for clinicians. Clinical work largely revolves around the twin axes of the client's self -definition (memories of the self) and the clinician's definition of the client's self (the clinician's memories of the client's story). For example, memory drives the client's self-report of an autobiographical history and presentation of self. Thi s theme also encourages the clinician to exercise caution when creating therapeutic environments that may lead to the creation of iatrogenic memories, an issue that has become increasingly important to the field.
Sch! acter's book is valuable for clinicians who have not been expo sed to recent primary literature on memory, memory processes, and multiple memory systems. As well as providing a solid background to this literature, it is also useful for those attempting to describe and interpret the clinical consequences of curre nt memory research. Additionally, the book provides a painless introduction to cognitive neuroscience, a field from which some clinicians have traditionally been distant.
The Revolution Continues.
We now suspect there are four or five mem ory systems (see Nadel, 1994; Nadel & Jacobs, 1996). Rapid developments in the field stood memory research on its head, and continued rapid developments may soon revolutionize our view of the self. Both developments have profound implications for th erapists. Clinicians without a solid background in work on multiple memory systems should be not be overwhelmed by waves of new memory research. Schacter does an admirable job of summarizing and presenting this research i! n an accessible, cogent way. Thus, Searching for Memory is indispensable for the clinician who thinks seriously about how memory works, the consequences of its systemic structure, its failures, and its quirks.
References
Cohe n, N., & Squire, L.R. (1980). Preserved learning and retention of pattern analyzing skill in amnesia: Dissociation of knowing how and knowing that. Science, 210, 207-209.Graf, P., & Schacter, D.L. (1985). Implicit and explicit memory for new associations in normal and amnesic subjects. Journal of Experimental Psychology: Learning, Memory, and Cognition, 16, 978-992.
Edelman, G.M. (1989). The remembered present: A biological theory of consciousness. New York: Basic Books.
Ja cobs, W.J., & Nadel, L. (1985). Stress-induced recovery of fears and phobias. Psychological Review, 92, 512-531.
Jacobs, W.J., & Nadel, L. (1997). Intrusive memory. Manuscript submitted for publication, University! of Arizona, Tucson.
Metcalfe, J., & Jacobs, W.J. (in press). The effects of stress on "cool" and "hot" memory systems. The Psychology of Learning and Motivation.
Milner, B., Corkin, S., & Teuber, H.L. (1968). Further analysis of the hippocampal amnesic syndrome: Fourteen year follow-up study of H.M. Neuropsychologia, 6, 215-234.
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Nadel, L. (1994). Multiple memory systems: What and why, an upda te. In D.L. Schacter & E. Tulving (Eds.), Memory systems 1994 (pp. 39-63). Cambridge, MA: MIT Press.
Nadel, L., & Jacobs, W.J. (1996). The role of the hippocampus in PTSD, panic, and phobia. In N. Kato (Ed.), Hippocampus: Functions and clini cal relevance. Amsterdam: Elsevier Science B.V.
Nadel, L., & O'Keefe, J. (1974). The hippocampus in pieces and patches: An essay on modes of explanation in physiological psychology. In R. Bellairs & E.G. Gray (Eds! .), Essays on the nervous system: A festschrift for Prof J.Z. Young (pp. 367-390). Oxford: Clarendon Press.
O'Keefe, J., & Nadel, L. (1978). The hippocampus as a cognitive map. Oxford: The Clarendon Press.
Schacter, D.L., & Tulving, E. (1994 ). Memory systems 1994. Cambridge, MA: MIT Press.
Scoville, W.B., & Milner, B. (1957). Loss of recent memory after bilateral hippocampal lesions. Journal of Neurology, Neurosurgery, and Psychiatry, 20, 11-21.
Squire, L.R. (1992). Mem ory and the hippocampus: A synthesis of findings with rats, monkeys, and humans. Psychological Review, 99, 195-231.
Tolman, E.C. (1948). Cognitive maps in rats and men. Psychological Review, 55, 189-208.
Tulving, E. (1972). Episodic an d semantic memory. In E. Tulving & W. Donaldson (Eds.), Organization of memory. New York: Academic Press.
Warrington, E.K., & Weiskrantz, L. (1968). New method of testing long-term retention with special reference ! to amnesic patients. Nature, 217, 972-974.
Warrington , E.K., & Weiskrantz, L. (1974). The effect of prior learning on subsequent retention in amnesic patients. Neuropsychologia, 12, 419-428.
Zola-Morgan, S., Squire, L.R., & Amaral, D.G. (1986). Human amnesia and the medial temporal region: Endu ring memory impairment following a bilateral lesion limited to field CA1 of the hippocampus. The Journal of Neuroscience, 6, 2950-2967.
Author Note
Kevin G.F. Thomas, Department of Psychology, University of Arizona and Department of Psychology, University of Southern California; W. Jake Jacobs, Department of Psychology, University of Arizona.This review was supported in part by a grant to the second author from The McDonnell-Pew Program in Cognitive Neuroscience.
Correspondence concerning this article should be addressed to:
Kevin G.F. Thomas,
University of Arizona,
Department of Psychology,
PO Box 210068,
Tucson, AZ 85721-0068.
E! -mai l: thomaske@u.arizona.edu.
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