PSYC 575
J OURNAL A RTICLE S UM M ARY A SSIGNM ENT I NSTRUCTIONS
OVERVIEW
For each Journal Article Summary, you will choose an article to review and use the Journal
Article Summary Form to complete the assignment. The article you select must be a peerreviewed journal article in the field of cognitive psychology. The article must also be a primary
source, meaning that the authors are discussing their own research, not others’ research (e.g.
review articles). Do not use an article that conducted a meta-analysis. It is ideal to select an
article that you will be using in your paper; however, this is not a requirement. If you use an
article that does not meet these criteria, you will not receive credit for this assignment. See the
example below for detailed explanation of the required material for each question. Submit the
completed form and a PDF of the article being reviewed. All material must be in current APA
format.
INSTRUCTIONS
1. APA reference of article being reviewed
Write the reference for the article as if it were in the reference section of your paper.
2. What is the research problem that is being investigated? What is the purpose of the
research being conducted?
Provide the “why” behind the paper. Why have they conducted this experiment? For
example: “These experiments were designed to explore the role of second order
conditioning in anxiety disorders.”
3. What is the research question?
The research question is more specific. What is the specific question or questions the
article will answer as a result of the study or experiment? For example: “Are adolescents
more sensitive to the memory imparting effects of alcohol?”
4. What are 2 or more theories that are discussed in the Introduction? How are they used to
motivate (or set up) the research question? Do the authors agree or disagree with these
theories?
Simply restate the theories discussed in the introduction in your own words. State how
these theories are driving the research questions. If the authors’ hypothesis is correct,
will it support the theory or be inconsistent with the theory? You should have good idea
of where the authors stand based on the evidence presented and the arguments they are
making.
5. How is the research question operationalized? First, identify the abstract constructs being
studied. Next identify the concrete way these are being observed or measured. This
should include your IV and DV.
PSYC 575
A construct is an abstract explanatory variable that this not directly observable (e.g.
memory). The concrete way the construct is measured will point you to the dependent
variable (DV). For example, if the paper is concerned with memory, the DV may be the
number of items recalled. The independent variable (IV) could be the amount of sleep
each participant was allowed the night before the test. Remember that we cannot directly
measure many of the constructs that are studied in psychology, so it is important that we
identify how they are being operationalize in each research study.
6. What is the research design (i.e. between or within subjects, what type of statistical tests
were used, what were the levels of each variable)?
This information will be in the methods section of your paper. Be sure to provide enough
detail to describe how the study was designed.
7. Describe the results (but not their broader implications). Were the results significant?
Which ones? Do these support or not support the hypothesis?
Describe the result in your own words. For example: Group X were able to recall
significantly more words than Group Y. This finding supports the hypothesis that
manipulation Y would reduce recall.
8. What limitations are mentioned? Why are these limitations theoretically interesting?
Limitations can be found in the discussion section of the paper. If a limitation is that they
didn’t have X control group, then explain in your own words why that is important. Does
it change the interpretation of the findings?
Note: Your assignment will be checked for originality via the SafeAssign plagiarism tool.
Hypothesis and Theory Article
published: 22 November 2010
doi: 10.3389/fnhum.2010.00211
HUMAN NEUROSCIENCE
Natural memory beyond the storage model: repression,
trauma, and the construction of a personal past
Nikolai Axmacher 1*, Anne T. A. Do Lam1, Henrik Kessler 2,3 and Juergen Fell 1
1
2
3
Department of Epileptology, University of Bonn, Bonn, Germany
Department of Medical Psychology, University of Bonn, Bonn, Germany
Department of Medical Psychology, University of Ulm, Ulm, Germany
Edited by:
Michael X. Cohen, University of
Amsterdam, Netherlands
Reviewed by:
Robert Blumenfeld, University of
California at Berkeley, USA
Patrick Khader, Philipps University,
Germany
*Correspondence:
Nikolai Axmacher, Department of
Epileptology, University of Bonn,
Sigmund-Freud-Str. 25, 53105 Bonn,
Germany.
e-mail: nikolai.axmacher@ukb.
uni-bonn.de
Naturally occurring memory processes show features which are difficult to investigate by
conventional cognitive neuroscience paradigms. Distortions of memory for problematic contents
are described both by psychoanalysis (internal conflicts) and research on post-traumatic stress
disorder (PTSD; external traumata).Typically, declarative memory for these contents is impaired –
possibly due to repression in the case of internal conflicts or due to dissociation in the case of
external traumata – but they continue to exert an unconscious pathological influence: neurotic
symptoms or psychosomatic disorders after repression or flashbacks and intrusions in PTSD after
dissociation. Several experimental paradigms aim at investigating repression in healthy control
subjects. We argue that these paradigms do not adequately operationalize the clinical process
of repression, because they rely on an intentional inhibition of random stimuli (suppression).
Furthermore, these paradigms ignore that memory distortions due to repression or dissociation
are most accurately characterized by a lack of self-referential processing, resulting in an impaired
integration of these contents into the self. This aspect of repression and dissociation cannot be
captured by the concept of memory as a storage device which is usually employed in the cognitive
neurosciences. It can only be assessed within the framework of a constructivist memory
concept, according to which successful memory involves a reconstruction of experiences such
that they fit into a representation of the self. We suggest several experimental paradigms that
allow for the investigation of the neural correlates of repressed memories and trauma-induced
memory distortions based on a constructivist memory concept.
Keywords: repression, memory distortions, PTSD, constructive memory, psychoanalysis, self-referential processing
Introduction
The current cognitive neurosciences have already revealed some
mechanisms underlying the modulation of memory performance.
However, several phenomena occurring in natural memory like
memory distortions due to repression and due to trauma-related
dissociations have not been adequately addressed yet by neurocognitive research.
Many studies have shown convincingly that emotionally arousing stimuli are better remembered than neutral images (Heuer and
Reisberg, 1990; Bradley et al., 1992; Christianson, 1992; Ochsner,
2000; Buchanan and Lovallo, 2001; Kensinger and Corkin, 2003).
This effect depends on a facilitation of hippocampus-dependent
memory processes by the amygdala (Seidenbecher et al., 2003;
Dolcos et al., 2004; Kensinger and Corkin, 2004; Phelps, 2004;
Smith et al., 2006; Figure 1A) and is related to the action of glucocorticoids (Kim and Diamond, 2002; Sapolsky, 2003). Such an
interaction between amygdala and hippocampus may be necessary
for the enhanced declarative memory of emotional events because
these two structures support complementary processes, as revealed
by a hippocampal-amygdala double dissociation: While integrity
of the hippocampus is necessary for the conscious memory that
a particular stimulus was, during conditioning, associated with a
shock, the amygdala is required for the unconsciously associated
vegetative reaction (Bechara et al., 1995; LaBar et al., 1995).
Frontiers in Human Neuroscience
While these studies provide compelling evidence for an enhanced
memory of stimuli which induce moderately negative emotions,
this is not necessarily true for two problematic cases involving
extremely negative emotions: the emergence of an unconscious
conflict, which is subject to repression, and traumatic events that
overstress a person’s executive capabilities and thus lead to dissociation. As a result, conscious recall of these contents is impaired,
but they continue to exert an unconscious effect which dramatically influences subsequent life – for example, by uncontrollably
occurring intrusions and dissociative flashbacks, panic attacks, or
psychosomatic symptoms (see Box 1). In other instances, victims of
a traumatic experience may be able to recall details from the trauma,
but only in a contorted manner – for example, from a detached
view outside of themselves, or without the associated emotions.
These symptoms of people which have suffered from real traumatic
experiences are subsumed under the diagnosis of post-traumatic
stress disorder (PTSD; F43.1, ICD-10, World Health Organization,
1992; DSM-IV-TR, American Psychiatric Association, 2000; Elbert
and Schauer, 2002; Maercker, 2009).
Therapeutic interventions on patients suffering from symptoms due to repressed conflicts or traumatic experiences require
an understanding of the mechanisms of repression and dissociation, not only on the psychological but also on the neurophysiological level (for the general benefit of cognitive neuroscience
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November 2010 | Volume 4 | Article 211 | 1
Axmacher et al.
Repression, trauma, and constructivist memory theory
Figure 1 | Emotional effects on memory. (A) Storage model of memory:
Moderately arousing emotional events are better encoded than neutral events.
(B) The narrative construction of a personal past relies on an interaction between
the hippocampus and self-referential processes in the medial prefrontal cortex
(mPFC). This process is facilitated by (moderately) emotional events due to inputs
from the amygdala. (C) In contrast, in the case of extremely negative (conflictual
or traumatic) experiences, the amygdala inhibits declarative memory formation
by the hippocampus and an integration of these memories with the self-image.
Box 1 | Memory distortions for problematic contents – repression and dissociation.
There are at least two distinct processes leading to memory distortions in the case of problematic contents involving extremely
negative emotions: repression and dissociation. Repression is the
process by which internal conflicts are stored in the unconscious.
Dissociation, on the other hand, is the process by which parts of
external traumatic events are stored in a non-declarative memory
system (see below). Repression is a typical defense mechanism
thoroughly described by Freud to explain clinical symptoms such as
neurotic depression or psychosomatic symptoms he observed in his
patients. According to Freud, the starting point is an internal conflict
arising when (mostly unconscious) wishes or drives are in a strict
opposition to internalized norms or standards. If this conflict cannot
be solved (e.g., because opposing elements cannot be integrated
with self-referential processes), it automatically produces intense
anxiety signaling danger for the subject (“Signalangst”). In an effort
to avoid extremely negative emotions, the entire conflict and its
associated emotions and memories are pushed into the unconscious
(repression). This leads to a lack of declarative memory for the conflict
and often the circumstances under which it emerged. The conflictual
material itself, however, continues to exist in the unconscious and,
Frontiers in Human Neuroscience
more importantly, exerts a major influence on the subject by causing
neurotic (e.g., depressed mood) or psychosomatic (e.g., paralyses)
symptoms. According to Freud, the symptom is a symbolization of the
internal conflict (for details, see Person et al., 2005). Dissociation is
a process mainly investigated in the context of PTSD. When external
traumata involving extremely negative emotions cannot be integrated
with self-referential processes and no coherent narrative can be built,
memories of this trauma become dissociated, i.e., they are stored in
a system with no direct verbal access. Brewin (2001, 2003) uses the
term “situationally accessible memory” to denote the memory system where such dissociated elements are stored. Verbal memories
of the traumatic event are often vague and include gaps. The contents
stored in the SAM, on the other hand, are the source for situationally triggered and hence not controllable intrusions and flashbacks
typical for PTSD. Although distinct from the process of dissociation described here on a conceptual level, the clinical phenomena
of “dissociations” in the traumatic situation (e.g., depersonalization,
derealization) are empirically linked to the dissociation of memories
in the SAM and hence the eventual development of a PTSD (Brewin
and Holmes, 2003).
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Axmacher et al.
Repression, trauma, and constructivist memory theory
for understanding cognition see Henson, 2005; Axmacher et al.,
2009). A number of studies investigated brain regions activated
during presentation of trauma-related cues in PTSD patients by
functional MRI (for a review, see Shin et al., 2005). Other studies
used MEG recordings to explore the neurophysiological basis of
the “trauma network” in PTSD. Elbert and colleagues found that
in these patients, processing of arousing stimuli (e.g., IAPS pictures) relied more on a fast sensory processing pathway, which is
uncoupled from prefrontal control, and less on elaborate processing along the ventral visual stream (Rockstroh and Elbert, 2010).
This may be due to a reduced connectivity with neural assemblies
representing context-related (“cold”) and trauma-related (“hot”)
information; as a result, trauma victims are unable to locate their
trauma memories in time and space and experience them as flashbacks (Elbert and Schauer, 2002). Psychotherapeutical treatment of
PTSD patients (e.g., by narrative exposure therapy; Neuner et al.,
2004) aims at re-integrating this network by placing the traumatic
memories in a coherent context. However, despite the incontestable
value of such studies directly investigating PTSD patients, they
are necessarily retrospective and do not allow for an experimental control of the emotionally disturbing situation itself. Several
experimental paradigms have been developed to capture the processes occurring during PTSD-like memory distortions in healthy
control subjects.
In this article, we will first describe memory distortions due
to repression of internal conflicts (Memory Distortions Due to
Repression of an Internal Conflict) and due to dissociation of
external traumata (Memory Distortions Due to Dissociation After
an External Trauma). In the Section “Experimental Paradigms of
Repression,” we provide an overview of the experimental paradigms currently used in the cognitive neurosciences to study
the neural correlates of repression in healthy volunteers. We will
argue that these paradigms do not convincingly operationalize
repression because they fall short of capturing key aspects of
this clinical phenomenon. Next, we will broaden our scope and
demonstrate that the concept of memory itself usually implied
in cognitive neuroscience studies represents only one aspect of
real-life memory, but disregards others and is therefore unable
to capture several complex features of memory (Storage and
Constructive Models of Memory): The criteria for successful
memory retrieval – namely accurate recollections of particular events – and the corresponding measures in the cognitive
neurosciences such as analyses of subsequent memory effects
only capture one relevant dimension of memory but disregard
its constructive aspects. This becomes most obvious in studies of autobiographical memory, which involves integration of
experiences with self-referential processes (Figure 1B). In the
Section “Trauma-Related Memory Distortions Due to Lack of
Self-Referential Processing,” we will argue that trauma-related
memory distortions can only be adequately understood (and
experimentally investigated) when they are conceptualized as a
failure to construct autobiographical memories, i.e., to integrate
these experiences with self-referential processes (Figure 1C). In
other words, these memory distortions cannot be adequately
understood as a failure to store memories, but as a failure to
integrate them with self-referential processes. We will present a
paradigm that takes these considerations into account. Finally
Frontiers in Human Neuroscience
(Promising Approaches for Studying Memory Distortions Due
to Repression), we will suggest a paradigm for the investigation
of memory distortions due to repression.
Memory distortions due to repression of an
internal conflict
The concept of repression was originally suggested by Herbart
(1824), but was introduced as a pathological process by Sigmund
Freud (see Box 1). Most of his patients had symptoms that could
not be explained by common logic or medical knowledge (e.g.,
paralyses of isolated limbs with no medical cause). In order to
explain the etiology of such symptoms, he conceptualized the
construct of repression as a mechanism being applied throughout
child development. It means the storage of complete internal conflicts (mostly between drives or wishes and internalized norms or
standards) and their surrounding emotions and memories in the
unconscious (Freud, 1915). The developing child hence represses
problematic content once an internal conflict is emergent. The
classical view of repression as depicted in Box 1 was significantly
advanced by an increased consideration of the child’s relationship
to its parents and its developing self (Ferenczi, 1933; Balint, 1969).
Internalization of a safe relationship to the parents is necessary for
the development of agency and a stable self (Stern, 1985), and the
infantile self is only developed through such parental feedback
(Fonagy et al., 2005). In this new view, repression may occur when
an internal conflict cannot be integrated with the image of the parents and/or self-referential processes. It is hence mainly this problematic integration in self-referential processes that give conflicts
their true “pathological” value and trigger repression as a means to
cope with them for the moment. The price to pay for the relative
peace the developing self obtains by repressing internal conflicts
is high, though: Clinically, it is important that the repressed material still exists in the unconscious and exerts a large influence on
the subject by causing psychosomatic (e.g., paralyses) or neurotic
(e.g., depressed mood) symptoms. The mechanism through which
repressed conflicts gain access to the “outside” in the form of symptoms is called conversion (Breuer and Freud, 1895). By symbolizing
the conflict or parts thereof in a symptomatic language, the patient
can gain some relief at the price of clinical symptoms.
Although rooted in early twentieth century psychology and
physiology, the concepts of repression and conversion via symbolization are still of high clinical relevance for recent models of
psychotherapy (for a current clinical textbook see Person et al.,
2005). Psychoanalytic therapies primarily working with the concept of repression are highly effective in treating patients with
severe psychiatric problems (e.g., chronic depression, personality disorders), as reviewed in a recent meta-analysis (Leichsenring
and Rabung, 2008). The recent trend that problematic integration in self-referential processes is regarded as the main virulent
component of repressed conflicts is reflected in newer manualized psychodynamic treatments (e.g., Wöller and Kruse, 2010):
The therapist should explicitly help the patient reorganize past
experiences in a way that repressed conflicts can be integrated in
self-referential processes. If successful, the patient not only gains
clinical improvement on a symptomatic level (less or no need for
conversion of an internal conflict in body symptoms), but also
achieves a new and more coherent view of the self.
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Axmacher et al.
Repression, trauma, and constructivist memory theory
Memory distortions due to dissociation after an
external trauma
In contrast to the psychoanalytical focus on internal conflicts early
in development, the concept of PTSD was primarily developed
with regard to external later-life traumata, initially those during the
Vietnam war. Memory distortions are, however, also among the main
symptoms of PTSD. On the one hand, memories of the traumatic
situation occur involuntarily as intrusions or even as flashbacks, in
which patients do not remember the traumatic event as something
past, but re-experience it as if it occurred again, similar to a dissociative state. On the other hand, declarative memory for details of the
traumatic situation is often impaired (Brewin, 2007; Jones et al.,
2007): A large body of studies have reported general declarative
memory deficits in PTSD patients (Clancy et al., 2000; Behrendt and
Moritz, 2005; Jelinek et al., 2006; for a review, see Brewin, 2007), and
in particular concerning verbal declarative memory (Yehuda et al.,
1995; Bremner et al., 2004). These memory impairments emphasize
initial encoding and retention of new contents (Bremner, 2002),
for instance, long lasting deficits in short-term memory have been
shown in adults suffering from abuse during childhood (Bremner
et al., 1995) as well as in Vietnam veterans diagnosed with PTSD
(Bremner et al., 1993). Additionally, source memory referring to
specific details of the traumatic event is often distorted in this
population (Johnson et al., 1993). However, as we will elaborate
below, the specific memory deformations following a trauma can
be most accurately conceptualized not as failures to recall specific
information, but as an impairment to integrate these experiences
with self-referential processes, i.e., in the framework of constructivist memory theories (Trauma-Related Memory Distortions Due to
Lack of Self-Referential Processing).
During the traumatic experience, limited time for conscious
processing of accompanying sensory or vegetative perceptions
inhibits an adequate integration thereof into autobiographical
memory. This effect may depend on two mechanisms. First, an
impaired processing of peripheral details during a traumatic situation due to a narrowing of the spotlight of attention is known
as the weapon focusing effect (Christianson, 1992). This effect
reduces the integration of all trauma-related information into a
coherent representation. Second, traumatic experiences may be so
overwhelming that the executive processing capabilities of trauma
victims fail, leading to peri-traumatic dissociative states. In these
states, subjects describe that they view themselves from a detached
Figure 2 | Memory distortions caused by repressed conflicts (left) and
traumatic experiences (right). Both psychoanalysis and PTSD theories suggest
that extremely negative contents may cause memory distortions characterized
Frontiers in Human Neuroscience
standpoint (e.g., Bremner and Brett, 1997; Lanius et al., 2002).
The dual representation theory (Brewin, 2003) accounts for these
trauma-related memory distortions by suggesting that memory
contents can be encoded either via a hippocampus-dependent
mechanism, which leads to a narrative integration of these contents
with other experiences and makes them accessible for declarative
recall (verbally accessible memory, VAM), or via an amygdaladependent process, which does not allow for a conscious control
of memory retrieval; however, unconscious experiences encoded
by the amygdala are automatically recalled whenever an associated
cue appears. According to the dual representation theory, this latter memory system has been described as situationally accessible
memory (SAM). This theory further suggests that amygdala and
hippocampus inhibit each other in the case of extremely negative
events, such that the degree to which the amygdala supports encoding of an event reduces the hippocampal contribution (Metcalfe
and Jacobs, 1998; Brewin, 2001; Figure 1C). Indeed, functional
MRI studies in PTSD patients indicate that recall of traumatic
events is associated with an increased activation of the amygdala
and a reduced activation of the hippocampus (Shin et al., 2005).
Alternatively, it is possible that in this case the amygdala facilitates
unconscious memory processes in the hippocampus (Henke et al.,
2003; Degonda et al., 2005).
Although the memory distortions described in psychoanalysis
(repression) and in PTSD research (memory fragmentations and
intrusions due to dissociation) appear to be very different at first
sight, they converge in the idea that pathological forms of unconscious memory replace declarative access to the problematic contents
(Figure 2). In both cases, contents that are not verbally accessible
(repressed conflicts or situationally accessible memories) exert a
pathological influence on the subject by causing psychosomatic
symptoms or intrusions and flashbacks, respectively. Thus, unconscious memories are created that do not refer to familiarity-based
recognition memory, but to memories that induce intrusions and
flashbacks following a trauma or neurotic symptoms following a
repressed conflict. As will be elaborated below, both phenomena gain
their true pathological value by a failure to integrate the problematic
contents (internal conflicts or traumata) in self-referential processes. Finally, successful treatment of both includes the integration
of problematic contents in a more coherent self. Therefore, we suggest that a common basis, or at least an overlap, exists for these two
groups of phenomena, which might be defined in neurobiological
by an impaired declarative memory for these events but pathological
unconscious memories. The theories differ with respect to the relative
contribution of the internal vs. external nature of the negative contents.
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Axmacher et al.
Repression, trauma, and constructivist memory theory
terms – possibly a modern replacement of the Freudian “metapsychology,” which was deeply grounded in late nineteenth century
neurophysiological knowledge (e.g., Stephan, 2002).
Experimental paradigms of repression
Cognitive neuroscience studies on repression have established two
main experimental paradigms which aim at investigating repression in normal healthy subjects, the “Directed forgetting” and the
“Think/No-Think” paradigm (Johnson, 1994; Anderson and Green,
2001; Erdelyi, 2006). In these paradigms, forgetting is consciously
and intentionally controlled by the participants, who are explicitly asked to voluntarily inhibit randomly selected subsets of items
or “not to think” of them: “On some trials they (i.e., the participants) were instructed to think of the previously learned picture;
on other trials they were instructed not to let the previously associated picture enter consciousness.” (Think/No-Think paradigm,
Depue et al., 2007). One might wonder whether these paradigms
are actually aimed at investigating the psychoanalytical process of
repression. However, this is explicitly stated; for example, the article
by Anderson et al. (2004) using the Think/No-Think paradigm
starts with the phrases: “Over a century ago, Freud proposed that
unwanted memories can be excluded from awareness, a process
called repression. It is unknown, however, how repression occurs
in the brain.” (p. 232). In both paradigms, the instructions reliably
lead to a decreased proportion of stimuli in the “voluntarily forgotten” condition which can be recalled in a subsequent declarative
memory test. The functional MRI results show a reduced BOLD
response in the hippocampus and an increased activity in the lateral
prefrontal cortex, which was interpreted as index for a recruitment of inhibitory executive control processes. However, for three
reasons we argue that these paradigms do not adequately operationalize the clinical process of repression. First, repression occurs
specifically in situations which overload the executive processing
capacities. During real repression, voluntary control is lacking; a
person represses an experience because this experience induces
an unbearable conflict. Therefore, attempting to induce repression by a recruitment of executive control processes is paradoxical.
The process investigated by Anderson and colleagues can more
precisely be termed “suppression,” the voluntary “forgetting,” or
“keeping down” of unwanted content. Second, if the mechanism of
repression is considered in isolation, it appears as if the contents of
repression are only secondary. However, repression does not occur
with regard to random situations or stimuli, but only if an intense
negative emotion is evoked. Thus, repression should be automatically induced by the experimental stimuli. Third, an experimental
paradigm of repression should not only reduce conscious access
to “repressed” stimuli, but also exclude that these stimuli are just
forgotten. In fact, it should even be shown that unconscious memory for these items is enhanced: The concept of repression was
introduced to explain clinical symptoms by experiences which are
not consciously accessible for the patients, but which continue to
exert an unconscious influence. Thus, in a non-declarative, implicit
memory test, an increased proportion of these stimuli should be
“remembered,” as shown in PTSD patients (e.g., McNally, 1997).
For example, these stimuli may be erroneously classified as “new”
during conscious recollection (because no conscious memory exists
for them), but this (incorrect) response may be given with a delayed
Frontiers in Human Neuroscience
reaction time as compared to stimuli which are in fact new, which
could be interpreted as indirect evidence of an unconscious conflict
during processing of these stimuli.
Alternative paradigms can take these critiques into account. In
such paradigms, the process of repression should not be voluntarily controlled; instead, they should create a situation in which
repression occurs automatically due to the emotional content of
a stimulus. When the “repressed” stimuli are subsequently presented in a recognition memory test, it is hypothesized that they
cannot be recalled consciously, but that they continue to exert an
unconscious influence on the subject’s behavior, as indicated by a
measure of unconscious memory. In addition, however, there is a
more general problem with the existing paradigms that are meant
to operationalize repression, because they measure memory as an
impairment of successful recall, but do not investigate whether
memories are successfully integrated into the self. In other words,
the constructive nature of successful memories is not taken into
account. In the next two sections, we will explain such a constructivist concept of memory, which is particularly relevant for
autobiographical memorizing (Storage and Constructive Models
of Memory) and is impaired in trauma-related memory distortions (Trauma-Related Memory Distortions Due to Lack of SelfReferential Processing). Finally, we will describe paradigms which
are suited to capture memory distortions related to repression of
conflicts (Promising Approaches for Studying Memory Distortions
Due to Repression).
Storage and constructive models of memory
In the cognitive neurosciences, memory is most often conceptualized as the process of stimulus encoding, storage, and retrieval.
In this framework, memory recall involves an identical repetition
of the original experiences – or, as Tulving (1983) described it
in his famous definition of episodic memory, as a “mental time
travel” back to the original situation. Accordingly, the neural
correlates of memory are usually studied by analyzing “subsequent memory”-effects, i.e., differences in brain activation patterns associated with the initial presentation of subsequently
remembered as compared to forgotten items. However, this
storage model of memory only captures one relevant dimension of memory, which relies on the identity of encoded and
remembered contents. In particular, it abstracts the specific function of memory retrieval for a subject. The cultural history of
memory models has always consisted in a dichotomy of such
storage models of memory on the one hand, models of constructive memory on the other hand (Assmann, 2002). Constructive
concepts of memory as re-interpretation of events were, e.g.,
investigated experimentally by Bartlett (1932). In a number of
studies, he presented his British subjects a short story, “The War
of the Ghosts,” which contains several seemingly illogical and
irrational elements. When subjects were afterward asked to recall
the story in as many details as possible, they modified it according to their own cultural schemata; illogical elements were thus
replaced by more coherent narratives. These studies illustrate
the constructive nature of memory retrieval and suggest that
memory is not only designed to retrieve events exactly as they
happened, but supports specific functions in the interaction with
the (internal or external) environment.
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Several current memory theories have incorporated aspects
of such a constructive account on memory and also highlighted
the relevance of self-referential processing. According to these
views, it is not exact representations of external events that are
encoded and retrieved, but the results from internal processing, evaluation, and interpretation of these events. For example,
the theory of transfer-appropriate processing (TAP) interprets
learning as re-performing a previous act, i.e., successful learning is an appropriate transfer of underlying structures rather
than an access of a memory trace (Morris et al., 1977; Bransford
et al., 1979; Baddeley, 2002). According to TAP, recall is facilitated
by similarity between the encoding and the retrieval state; this
effect is related to both environmental contexts (e.g., if encoding occurred in the library of the Psychology Department, recall
will also be easier at that place) and internal variables such as
current affective states and goals (events encoded in a sad mood
will also be most likely retrieved in a sad mood). In addition,
many studies investigated the effects of encoding conditions
related to self-referential processing, e.g., by instructing subjects to rate the pleasantness of items (Hunt and Einstein, 1981;
McDaniel and Einstein, 1993). Such effects have been described,
e.g., in the framework of the levels of processing theory (Craik
and Lockhardt, 1972). Furthermore, several experimental paradigms have investigated why events which have never happened
are “recalled” (the false memory paradigm; see, e.g., Deese, 1959;
Roediger III and McDermott, 1995), and why actual events are
forgotten (e.g., retrieval-induced forgetting paradigms, Anderson
et al., 1994; Macrae and MacLeod, 1999; Caroll et al., 2007).
None of these theories and paradigms assumes a simple storage
model of memory. Instead, they capture aspects of a constructive
memory theory because they emphasize that memory encoding
and retrieval depend on the construction of an integrated experience and the evaluation of its personal relevance. Furthermore,
recall can be considered a “reconstruction” because it depends
on the situational context during which it occurs.
However, there is a fundamental difference between these
accounts and constructivist memory theories in a narrower sense,
which is the criterion for successful memory: In storage models
of memory, recall is successful if it recapitulates crucial aspects of
a previous experience; according to constructivist memory theories, however, recall is successful if it allows the recalling person
to build a coherent narrative about his/her past. Imagine that
two people experience the same event, but afterward report two
inconsistent versions of this event. According to the storage model
of memory, there are objective criteria whether the report of the
first or the second person is correct. In contrast, the constructive
memory theory would assume that both reports may be correct
as long as subjective coherence is achieved. This view differs considerably from paradigms such as the false memory paradigm, the
retrieval-induced forgetting paradigm, or paradigms of voluntary
memory suppression such as the “think/no-think” or “directed forgetting” paradigms: These paradigms investigate the conditions
under which memory storage fails, but not the conditions under
which a successful transformation into an acceptable narrative,
and integration with self-referential processes, succeed. Similarly,
even though theories such as the TAP theory or models such as the
Adaptive Control of Thought model (Anderson, 1976) emphasize
Frontiers in Human Neuroscience
the selective nature of encoding and retrieval, they do not require
that experiences be integrated into a coherent and acceptable personal history for memory to be successful.
Recall of autobiographical memory is a prototypical example
of a reconstructive memory process. Depending on situational
requirements and personal aims, recollection of a personal experience serves specific functions. The main criterion for successful
autobiographical memory recall is not whether a situation is exactly
reproduced; instead, as it is one of the main functions of autobiographical memories to serve the construction of a coherent and
acceptable self-image, these memories have to fit into a coherent
construction of the past – for this reason, the subjects in Bartlett’s
studies modified the story according to their cultural expectations.
Several more recent studies provide experimental evidence for this
view. First, it has been shown in cross-cultural studies that autobiographical memory is influenced by the emphasis which is put in
each culture on the self and on a unique life story (Nelson, 2003).
Second, in each culture, autobiographical memory recall depends
on an individual’s current view of herself/himself, and serves the
construction of a coherent and positive self (Wilson and Ross,
2003). For example, as improving selves are particularly gratifying
(e.g., Frijda, 1988), subjects tend to view their own past abilities as
inferior than their current abilities, and as lower than they viewed
them before (Conway and Ross, 1984). Third, it was shown that
the reported number of autobiographical memory recalls which
aimed at creating self-continuity was higher in subjects with low
degrees of self-concept clarity (corresponding to low levels of perceived self coherence), suggesting that autobiographical memory
recall indeed served to strengthen self coherence (Bluck and Alea,
2008). Fourth, brain lesions which induce a loss of autobiographical memory may also lead to an impairment of the sense of one’s
self (Schacter, 1996).
The functions of autobiographical memory retrieval have been
described in a review by Bluck (2003). First, memorizing serves
the creation of a continuous identity: “[T]hough we often think of
memory as a series of events, it is also a record of a series of selves,
or a record of the self across time, an autobiography.” (Bluck, 2003,
p. 12). Second, memory is relevant for the creation and maintenance
of social interactions: Often, personal statements are being justified by referring to autobiographical events, and a common past is
created by evocation of situations that were experienced together.
Finally, autobiographical memories serve a directive function, as
they allow one to predict what will happen in the future and which
actions will likely lead to the desired outcomes.
Cognitive neuroscience studies on the neuronal correlates of
autobiographical memory recall support the view that this type
of memory involves the construction of a self-image. These studies revealed an increased activation of both the hippocampus
and the medial prefrontal cortex (mPFC) during processing of
self-related autobiographical information (Cabeza et al., 2004;
Summerfield et al., 2009). Activation of the mPFC was associated
with self-referential processes, for example during presentation of
photographs that subjects had taken themselves as compared to
photographs taken by other subjects (Cabeza et al., 2004) or during evaluation whether adjectives could be attributed to oneself
instead of to another person (Gutchess et al., 2007). The theory that
autobiographical memory depends on an integration of declarative
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Repression, trauma, and constructivist memory theory
memory and self-referential processes is depicted in Figure 1B. It
should be noted, however, that reverse inference from activation of
a given region during one experimental condition to mental processes occurring in this condition may be problematic because these
activations are usually not unequivocal (for reviews on the validity
of this inference see Henson, 2005; Axmacher et al., 2009).
While constructive concepts of memory exerted a strong influence on research in social psychology, most studies in the cognitive neurosciences (apart from autobiographical memory studies)
followed the storage model. This is particularly problematic in
the case of memory distortions due to repression and dissociation: Memory, conceptualized as a constructive process, serves
to build personal identities. In contrast, repressed conflicts and
traumatic events cannot become part of this personal identity;
their subjective meaning is not re-evaluated and integrated into
a narrative continuity with other events, but remains restricted
to the situation when these events were experienced. Repressed
conflicts and traumatic events remain permanently present in
a pathological sense – they cannot be forgotten or temporarily
dismissed. Thus, the case of memory distortions shows that constructive memory and storage memory are not only alternative
concepts of memory, but are actually directly opposing each other
in some respects. In the following two paragraphs, we describe
further evidence for this view and present promising paradigms
for the investigation of trauma-related and repression-related
memory distortions.
Trauma-related memory distortions due to lack of
self-referential processing
Several observations suggest that what is central for trauma-related
memory distortions is not the lack of a memory for a traumatizing
situation per se, but the lack of an integration of this memory with
self-referential processes. First, during traumatic events, subjects
may lose their sense of agency, i.e., they do not feel themselves
as autonomous human beings but just as observers. Dissociation
during the traumatic event is predictive for subsequent memory
impairments and also for the development of PTSD – even more
than trauma severity is (Maercker et al., 2000; Ozer et al., 2003).
Second, PTSD patients often describe that the traumatic scenes are
remembered from a detached view outside of themselves (Brewin
and Saunders, 2001; Bohleber, 2008). Thus, they also recall themselves as lacking self-referential processing during the trauma.
Third, loss of agency during traumatic events may also explain
why traumatic events cannot only induce PTSD, but also a complex
PTSD (Herman, 1992) or developmental trauma disorder (van der
Kolk, 2005) which both involve changes to the self-image and an
impaired feeling of identity. Finally, flashbacks can be understood
as a dissociative re-living of the traumatic situation, i.e., re-living
in a state of depersonalization and derealization (Maercker, 2009).
Taken together, these considerations suggest that traumatic events
mainly impair the integration of experiences with the internal
perception and valuation of these events, and that the resulting
memory distortions need to be conceptualized within a constructive memory framework (Figure 1C).
How can the reduced self-referential processing during traumatic experiences, with the resulting impairment in the construction of memories for these events, be assessed experimentally?
Frontiers in Human Neuroscience
The effect of dissociation on the development of trauma-related
memory distortions was studied in healthy control subjects by use
of the trauma film paradigm (for an overview of this method, see
Holmes and Bourne, 2008). This paradigm builds on observations
that intrusive thoughts do not only occur in PTSD patients, but also
in many situations of everyday life after strong emotional events
(Berntsen, 1996; Mace, 2005). In the trauma film paradigm, intrusions are induced by a movie which contains emotionally disturbing
scenes (e.g., scenes of victims from car accidents). This paradigm
has already been used in a number of studies and reliably induces
intrusive memories, which disappear after a few weeks (of course,
ethical reasons prohibit the induction of an actual PTSD which is
defined by the persistence of symptoms, after a trauma, for more
than a month). In addition to intrusions, declarative memory for
the contents of the trauma film is impaired (Brewin, 2007; Jones
et al., 2007). Using this paradigm, it was shown that spontaneously
occurring states of dissociation predicted subsequent intrusions
(Holmes et al., 2004; Kindt et al., 2005). However, any attempts to
increase intrusion incidence by experimentally induced dissociation failed (e.g., Holmes et al., 2007), suggesting that dissociation
may affect memory distortions via an underlying psychological or
physiological process, which is not triggered by the experimentally
induced dissociation – e.g., via reduced activation of brain regions
supporting self-referential processing.
The neural basis of memory effects in the trauma film paradigm
was investigated in two recent functional MRI studies (Henckens
et al., 2009; van Marle et al., 2009). Physiological parameters as
well as subjective reports confirmed that stress was induced by
segments of a distressing movie. In the first study, IAPS pictures
were presented interleaved with these segments and brain activity related to declarative encoding of IAPS pictures was analyzed
(Henckens et al., 2009). In contrast to the impairment of declarative
memory for traumatic events observed clinically, the authors found
that stress increased subsequent recollection of pictures. However,
hippocampal activity was reduced during successful encoding of
images under stress, suggesting that memory formation required a
hippocampal-independent mechanism. These results are therefore
consistent with the dual representation theory and suggest that a
high stress level shifts encoding from a hippocampus-dependent
to an amygdala-dependent encoding mechanism (Brewin, 2003),
although no implicit memory tests were performed, and thus the
exact memory processes contributing to the stress-induced memory
enhancement could not be resolved. In line with this interpretation,
the second study showed increased responsiveness of the amygdala
to facial stimuli presented interleaved with the movie, although
memory for these items was not tested (van Marle et al., 2009).
Further research using the trauma film paradigm will be extremely
useful to test predictions from the dual representation theory more
directly: First, it will be interesting to test memory for the movie
segments themselves (instead of interleaved stimuli). Second, not
only declarative memory but also intrusions should be captured
using the diary method (Brewin and Saunders, 2001; Bisby et al.,
2009); i.e., intrusions during the weeks following the experiment
should be collected by diaries given to the participants. Finally –
and maybe most importantly – the effects of dissociation during
the movie should be investigated. As described above, it appears
to be extremely difficult to induce dissociation by experimental
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Repression, trauma, and constructivist memory theory
modifications. Therefore, dissociation could be measured on the
neural level, by a reduced activation of regions supporting selfreferential processing.
Promising approaches for studying memory
distortions due to repression
The neural signature of self-referential processing during memory
recall can be used as a measure of successful reconstructive recall – or
the lack thereof – not only in the trauma film paradigm, but also in
paradigms investigating memory distortions due to repression. In one
important paradigm (see Figure 3), which was initially suggested by
Jung (1918), words in a list are presented consecutively and subjects
are instructed to generate an associated word to each word in the list
using the psychoanalytical technique of “free association” – i.e., they
are asked to say the first word which comes into their mind. The idea
of “free association” is rooted in Freud’s psychoanalytical technique:
When patients with neurotic symptoms say spontaneously what comes
to their minds, they may eventually reveal material that can be linked by
a skilled therapist to repressed conflicts which lead to or maintain their
symptoms (Freud, 1913). The clinical usefulness of this technique has
been shown many times (e.g., Person et al., 2005). According to Freud
(1913), patients typically start to repress spontaneous thoughts once
they may link to conflicts or memories that have to be kept unconscious.
In Jung’s (1918) original experiment, the process of “free association” is
believed to reveal contents that are primarily unconscious but relevant
for the subjects because they may be related to repressed conflicts. The
behavioral result of the hypothesized repression – resistance against
revelation of these contents – can be confirmed experimentally by
an increase in skin conductance response (SCR) and reaction times.
The link between repression and the hypothesized increase in skin
conductance is an indirect one: It is known that psychological arousal
(activation) leads to increased skin conductance (Lang et al., 1995).
Clinical experience suggests that patients may show increased signals
of stress and arousal when repressing critical contents (Person et al.,
2005). Thus, it is assumed that repression may be operationalized by
increases in skin conductance. Next, the same list is presented again,
but now subjects are not asked to name a new word by free association,
but to recall the word they have initially generated. Finally, all initially
associated words are presented again, and subjects are instructed to
indicate the emotional valence and intensity of these words (as an
indicator of conscious emotional content). In contrast to the often
described increase in declarative memory for negative emotional material (Heuer and Reisberg, 1990; Bradley et al., 1992; Christianson, 1992;
Ochsner, 2000; Buchanan and Lovallo, 2001; Kensinger and Corkin,
2003), this paradigm reliably results in an impaired memory for words
whose initial generation is associated with physiological signs of resistance (increase in skin conductance and reaction times) and which are
subsequently rated as emotionally negative (Levinger and Clark, 1961;
Köhler and Wilke, 1999; Köhler et al., 2002). In particular, Levinger
and Clark (1961) found that high SCRs during association predicted
failure of subsequent recall. Furthermore, recall was worse for words
which were afterward labeled as emotional as compared to words
Figure 3 | Repression of self-generated emotional words. (A) Presentation of cue words, participants were instructed to speak out loudly the first word which came to
their minds while skin conductance response (SCR) and reaction latencies were recorded. (B) At memory test, the same cue words were presented again, and participants
had to recall the word which they previously associated with the cue word during phase (A) of the experiment. (C) Emotional rating of the self-generated words.
Table 1 | Experimental paradigms for studying memory distortions.
Paradigm
Automatic Implicit memory
Declarative memory
Self-referential
stimulus effects?
enhanced?
impaired?
processing considered?
No
? (not tested)
Yes
No
Trauma film paradigm
Yes
Yes (intrusions)
Yes
Yes (dissociation)
Levinger/Clark/Köhler (Figure 3)
Yes
Yes (reaction times)
Yes
Yes (subject-specific cues)
Directed forgetting;
Think/No-Think
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Repression, trauma, and constructivist memory theory
which were labeled as neutral. Several alternative explanations might
account for these results. First, word frequency of the presented words
may determine recall of associations. However, frequency was equilibrated between emotional and neutral words. Second, it is possible
that recall depended on the number of possible associations to a word
(“response entropy”). For words associated with high response entropy,
the possible associations interfere with each other, making it more
difficult to recall the initially associated word. In fact, Levinger and
Clark found that forgotten words had higher response entropies than
remembered words. However, partial correlations revealed that emotion and response entropy contributed independently to memory.
Several shortcomings of the study by Levinger and Clark (1961)
should be noted. First, recall was only tested immediately after initial
associations, leaving open the possibility that it does not induce sustained effects on memory. Second, reaction times as another possible
measure of resistance toward revelation of repressed conflicts were
not tested. In a follow-up study designed to overcome these shortcomings, Köhler and Wilke (1999) conduced a similar experiment,
but (1) also measured reaction times during initial association, (2)
asked subjects to recall the associated words not only directly after the
association, but again after one week. They found that increased SCRs
and reaction times during association as well as emotional ratings
predicted both immediate forgetting and forgetting after 1 week.
To our knowledge, this paradigm has never been used for cognitive neuroscience experiments. However, the dual representation
theory (Brewin, 2003) predicts that generation of subsequently forgotten words is associated with increased amygdala and decreased
hippocampal activation, and a negative correlation of activity in
these regions. Furthermore, based on the idea that repression is
related to reduction in self-referential processing, we would expect
that generation of these words leads to decreased activation of the
mPFC, and to a reduced functional connectivity between this region
and the hippocampus.
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Conflict of Interest Statement: The
authors declare that the research was
conducted in the absence of any commercial or financial relationships that
could be construed as a potential conflict
of interest.
Received: 05 May 2010; accepted:
11 October 2010; published online: 22
November 2010.
Citation: Axmacher N, Do Lam ATA,
Kessler H and Fell J (2010) Natural memory beyond the storage model: repression,
trauma, and the construction of a personal
past. Front. Hum. Neurosci. 4:211. doi:
10.3389/fnhum.2010.00211
Copyright © 2010 Axmacher, Do Lam,
Kessler and Fell. This is an open-access
article subject to an exclusive license
agreement between the authors and the
Frontiers Research Foundation, which
permits unrestricted use, distribution,
and reproduction in any medium, provided the original authors and source
are credited.
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