Neurocomputing 38}40 (2001) 1223}1228

Long term memory:
Encoding and storing strategies of the brain

Stefano Fusi
Institute of Physiology, University of Bern, Bu( hlplatz 5, 3012 Bern, Switzerland

Abstract

Plastic material devices, either arti”cial or biological, should be capable of rapidly modifying
their internal state to acquire information and, at the same time, preserve it for long periods (the
stability}plasticity dilemma). Here we compare, in a simple and intuitive way, memory stability
against noise of two di!erent strategies based, respectively, on fully analog devices that
accumulate linearly small changes and on systems with a limited number of stable states and
threshold mechanisms. We show that the discrete systems are more stable, even with short
inherent time constants, and can easily exploit the noise in the input to control the learning rate.
We “nally demonstrate the strategy by discussing a model of a biologically plausible spike-
driven synapse. ? 2001 Elsevier Science B.V. All rights reserved.

Keywords: Synaptic plasticity; Long term memory; Learning

1. Introduction

Material (arti”cial or biological) learning devices, like the synapses, have the
capability of changing their internal states in order to acquire (learn) and store
(memorize) information about the statistics of the incoming #ux of stimulations. In
a realistic situation, the stimulations carrying relevant information are separated
by long time intervals of noisy input which tends to erase the memory of the
previously acquired information.Moreover the interference of novel stimulations with
already acquired older ;memories’ may give rise to memory loss (e.g. the oldest
stimulations are forgotten to make room for the new ones). This is also known as the

0925-2312/01/$ – see front matter ? 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 5 – 2 3 1 2 ( 0 1 ) 0 0 5 7 1 – 9

stability}plasticity dilemma: the memory should be stable against irrelevant inputs
(e.g. noise) for long periods and, at the same time, the internal state should be rapidly
modi”ed to acquire the information conveyed by the relevant inputs. This dilemma
becomes particularly arduous when dealing with material memory devices that do not
allow arbitrarily large time constants or parameters “ne tuning, especially if the
devices are small (e.g. it is reasonable to assume that permanent changes can not be
arbitrarily small).
Here we show one possible encoding and storing strategy that solves this dilemma

and we exemplify it by discussing a model of a spike-driven learning synapse. The
strategy is based on the assumption that information to be coded is redundant: e.g. for
the s

J Sleep Res. 2022;31:e13527. wileyonlinelibrary.com/journal/jsr | 1 of 12
https://doi.org/10.1111/jsr.13527

1 | INTRODUC TION

Previous studies report that false memories can be influenced by
sleep (for a review see Conte ; Ficca, 2013; Landmann et al., 2014).
Among the first to investigate the relationship between sleep and
false memories, Diekelmann, Born, and Wagner (2010), Diekelmann,
Landolt, Lahl, Born, and Wagner (2008) showed that sleep- deprived

individuals produce more false memories at morning re- test com-
pared to participants in an undisturbed sleep condition. The au-
thors specified that this effect could be mainly linked to an impaired
memory retrieval process. In fact, acute sleep loss can affect several
cognitive functions related to prefrontal activity that are essential
to accurate recall from long- term memory (Durmer ; Dinges, 2005;
Frenda ; Fenn, 2016).

Received: 28 June 2021 | Revised: 16 November 2021 | Accepted: 18 November 2021
DOI: 10.1111/jsr.13527

R E S E A R C H A R T I C L E

False memories formation is increased in individuals with
insomnia

Serena Malloggi1 | Francesca Conte2 | Oreste De Rosa2 | Stefania Righi1 |
Giorgio Gronchi1 | Gianluca Ficca2 | Fiorenza Giganti1

1Department of NEUROFARBA,
University of Florence, Florence, Italy
2Department of Psychology, University of
Campania L. Vanvitelli, Caserta, Italy

Funding information
V:ALERE 2019

Summary
Previous studies suggest that sleep can influence false memories formation.
Specifically, acute sleep loss has been shown to promote false memories production
by impairing memory retrieval at subsequent testing. Surprisingly, the relationship
between sleep and false memories has only been investigated in healthy subjects
but not in individuals with insomnia, whose sleep is objectively impaired compared
to healthy subjects. Indeed, this population shows several cognitive impairments
involving prefrontal functioning that could affect source monitoring processes and
contribute to false memories generation. Moreover, it has been previously reported
that subjects with insomnia differentially process sleep- related versus neutral stimuli.
Therefore, the aim of the present study was to compare false memories production
between individuals with insomnia symptoms and good sleepers, and to evaluate
the possible influence of stimulus category (neutral versus sleep- related) in the two
groups. The results show that false memories are globally increased in participants re-
porting insomnia symptoms compared to

Cognitive reserve modulates ERPs associated with verbal
working memory in healthy younger and older adults

Megan E. Speer1 and Anja Soldan2

2Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205

Abstract

Although many epidemiological studies suggest the beneficial effects of higher cognitive reserve

(CR) in reducing age-related cognitive decline and dementia risk, the neural basis of CR is poorly

understood. To our knowledge, the current study represents the first electrophysiological

investigation of the relationship between CR and neural reserve (i.e., neural efficiency and

capacity). Specifically, we examined whether CR modulates event-related potentials (ERPs)

associated with performance on a verbal recognition memory task with three set sizes (1, 4, or 7

letters) in healthy younger and older adults. Neural data showed that as task difficulty increased,

the amplitude of the parietal P3b component during the probe phase decreased and its latency

increased. Notably, the degree of these neural changes was negatively correlated with CR in both

age groups, such that individuals with higher CR showed smaller changes in P3b amplitude and

less slowing in P3b latency (i.e., smaller changes in the speed of neural processing) with

increasing task difficulty, suggesting greater neural efficiency. These CR-related differences in

neural efficiency may underlie reserve against neuropathology and age-related burden.

Keywords

Cognitive reserve; Verbal working memory; Neural efficiency; Event-related potentials (ERPs);
P3; Cognitive aging

© 2015 Elsevier Inc. All rights reserved.

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Priming analogical reasoning with false memories

Mark L. Howe ; Sarah R. Garner ; Emma Threadgold ;

Linden J. Ball

Published online: 18 March 2015
# The Author(s) 2015. This article is published with open access at Springerlink.com

Abstract Like true memories, false memories are capable of
priming answers to insight-based problems. Recent research
has attempted to extend this paradigm to more advanced
problem-solving tasks, including those involving verbal ana-
logical reasoning. However, these experiments are
constrained inasmuch as problem solutions could be generat-
ed via spreading activation mechanisms (much like false
memories themselves) rather than using complex reasoning
processes. In three experiments we examined false memory
priming of complex analogical reasoning tasks in the absence
of simple semantic associations. In Experiment 1, we demon-
strated the robustness of false memory priming in analogical
reasoning when backward associative strength among the
problem terms was eliminated. In Experiments 2a and 2b,
we extended these findings by demonstrating priming on new-
ly created homonym analogies that can only be solved by
inhibiting semantic associations within the analogy. Overall,
the findings of the present experiments provide evidence that
the efficacy of false memory priming extends to complex an-
alogical reasoning problems.

Keywords Priming . Analogical reasoning . False memory .

DRMparadigm . Homonyms . Spreading activation

Memory is highly flexible and reconstructive, designed to
retain information about the past, interpret the present, and

support simulations of future events (e.g., Howe, 2011;
Newman ; Lindsay, 2009; Schacter, Guerin, ; St. Jacques,
2011). Interestingly, recent research has shown that memory is
highly functional, regardless of whether we are talking about
memories for events that actually occurred (i.e., true memo-
ries) or for self-generated memories of events that did not
occur (i.e., false memories). For example, a significant body
of research has demonstrated that true memories are able to
prime performance on related memory tasks (e.g., implicit
memory; see Gulan ; Valerjev, 2010) as well as non-
memory tasks such as verbal problem solving (e.g.,
Mednick, Mednick, ; Mednick, 1964).

Priming refers to Ba change in the ability to identify, pro-
duce, or classify an item as a result of a prior encounter with
that item, or a related item^ (Schacter, Gallo, ; Kensinger,
2007, p. 356). In the case of analogical reasoning, for exam-
ple, there is a well-established body of evidence demonstrat-
ing that people are able to transfer directly their prior memo-
ries of problems and their solutions in order to assist them in
tackling new, related problems (e.g., Bassok ; Holyoak,
1989; Richland, Zur, ; Holyoak, 2007; for a recent review,
see Holyoak, 2012). Alt

https://doi.org/10.1177/2167702618797106

Clinical Psychological Science
2019, Vol. 7(1) 29 –31
© The Author(s) 2018
Article reuse guidelines:
sagepub.com/journals-permissions
DOI: 10.1177/2167702618797106
www.psychologicalscience.org/CPS

ASSOCIATION FOR
PSYCHOLOGICAL SCIENCECommentary

Patihis and Pendergrast’s (2019; this issue, p. 3) research
raises questions about balancing risks of false memories
with risks of not treating childhood trauma that may
have been forgotten. Their central concern is that when
clinicians ask about repressed memory, many clients
will form false memories of child abuse.

They emphasize suggestibility/false memory, but
their review omits important studies that moderate their
concerns. For example, when Pezdek, Finger, and
Hodge (1997) tried to implant a false memory in adults
of receiving a childhood enema, the error rate was zero.
Although some adults, including with trauma histories,
agree with schema-consistent false suggestions about
childhood events, when it comes to taboo acts of a
sexual nature, Goldfarb, Goodman, Larson, Eisen, and
Qin (in press) again found zero false memories. Many
suggestibility/false memory studies use creative coding,
such as when “partial false memories” (“That never
happened to me, but if my mother said it did, it could
have been at the mall”) are nearly buried in statistics
reported.

That said, we acknowledge the reality of false abuse
memories in some individuals as possibly induced or
encouraged by therapists, particularly those who use
hypnosis or psychotropic drugs (e.g., in combination
with religious or other doctrines; Bottoms, Shaver, ;
Goodman, 1996). Still, it is unclear that clinicians should

refrain from discussion with clients about lost memory
(a term we prefer because it does not invoke “repres-
sion” mechanistically), given that therapy can help
memory: Child victims who sought therapy during/soon
after legal involvement (vs. did not) had more accurate
long-term memory for abuse a decade later (Goodman,
Goldfarb, Quas, ; Lyon, 2017).

We note that Patihis and Pendergrast (2019) leave
largely unaddressed that lost memories of childhood
trauma can occur, as can recovery of them. In longitu-
dinal studies of documented child sexual abuse (CSA),
15% to 38% of victims failed to recall the target case. Of
those who recalled it, 15% to 16% said there were times
of not remembering it (Goodman et al., 2003; Williams,
1994). More severe abuse was associated with reporting
having forgotten the CSA but also actually predicted
greater memory accuracy for it (Ghetti et al., 2006).

Relevant are our past findings regarding misinterpreta-
tion of research questions. Victims often misinterpreted
questions about “repressed memory” and “amnesia,”
wrongly assuming we were asking if there was a time
when they were not consciously thinking ab

Sleep deprivation increases formation of false memory

JUNE C . LO , PEARLYNNE L . H . CHONG , SHANKAR I GANESAN ,
RUTH L . F . L EONG and M I CHAEL W . L . CHEE
Centre for Cognitive Neuroscience, Neuroscience and Behavioral Disorders Program, Duke-NUS Medical School, Singapore

Keywords
adolescents, adults, cognitive function, false
memory, memory formation, sleep deprivation

[The copyright line for this article was changed
on 17 February 2017 after original online
publication.]

Accepted in revised form 22 May 2016; received
25 September 2015

DOI: 10.1111/jsr.12436

SUMMARY
Retrieving false information can have serious consequences. Sleep is
important for memory, but voluntary sleep curtailment is becoming more
rampant. Here, the misinformation paradigm was used to investigate
false memory formation after 1 night of total sleep deprivation in healthy
young adults (N = 58, mean age ? SD = 22.10 ? 1.60 years; 29
males), and 7 nights of partial sleep deprivation (5 h sleep opportunity)
in these young adults and healthy adolescents (N = 54, mean
age ? SD = 16.67 ? 1.03 years; 25 males). In both age groups,
sleep-deprived individuals were more likely than well-rested persons to
incorporate misleading post-event information into their responses during
memory retrieval (P < 0.050). These findings reiterate the importance of
adequate sleep in optimal cognitive functioning, reveal the vulnerability of
adolescents’ memory during sleep curtailment, and suggest the need to
assess eyewitnesses’ sleep history after encountering misleading
information.

INTRODUCTION

Memories of an event rarely provide a literal record of that
experience. Instead, they involve the integration of elements
of that episode with prior experience or knowledge. A highly
novel or distinct experience, for example a first publication in
a high-impact journal, is rarely mis-remembered. However,
when the memory of a specific episode is confused with prior
similar experiences, and/or fails to be distinctly encoded,
errors in subsequent memory retrieval can occur. The
emergence of such false memories often reminds us of
human fallibility, as highlighted by the inconsistencies in
recollection of personal events surrounding the Challenger
disaster (Neisser and Harsch, 1992). However, they can also
have more serious consequences such as wrongful convic-
tion due to inaccurate eyewitness testimony.
Adequate sleep is essential to optimize memory processes

(Diekelmann and Born, 2010; Stickgold and Walker, 2013).
This is consistent across a range of tests eval

COMP R E H EN S I V E R E V I EW

Induction of false beliefs and false memories in laboratory
studies—A systematic review

Beate Muschalla | Fabian Schönborn

Institute of Psychology, Technische Universität

Braunschweig, Braunschweig, Germany

Correspondence

Prof. Dr. Beate Muschalla, Technische

Universität Braunschweig, Institute of

Psychology, Humboldtstraße 33, 38106

Braunschweig, Germany.

Abstract

Psychological interventions often use guided discovery and other techniques for

diagnostic exploration and intervention planning. This way, memories may arise in

the person, which may be true or false. False memories of earlier events can be harm-

ful and result in real suffering, similar to actual traumatic memories. Based on cogni-

tive psychological and psycho-traumatological findings, there is pronounced dissent

in the academic disciplines regarding the conceptualization, relevance and research

of false memories. This review contributes to the basic question of how often false

beliefs and false memories may be induced within the frame of different interactional

techniques. A systematic review has been conducted of 59 articles from (quasi-)

experimental studies and two qualitative sources from 30 data bases. Three main

methods of memory induction provide the basis for reporting: imagination inflation,

false feedback, and memory implantation. Due to the conceptual and methodological

diversity of the studies, the results appear to be heterogeneous. Free and guided

imagery, as well as suggestive statements, could induce false beliefs or false memo-

ries in, on average, 20%–50% of the participants who underwent experimental

manipulation concerning false past events. A false belief induction may occur after

dream interpretation or hypnosis in more than 50% of participants. Personalized sug-

gestion is more effective in inducing memory than the general plausibility of the

suggested events. Further research questions are which therapeutic actions seem

appropriate in cases of harmful false memories. This depends not only on whether

there are veridical elements in the false memory but also on the quality and meaning

of the memory for the person’s life and ability to cope with burdens.

K E YWORD S

false beliefs, false memories, guided imagery, memory induction, side effects, suggestion

1 | INTRODUCTION

False belief is present when an individual is erroneously convinced that

an event has happened to or with them earlier in their life, even if

they pr