Episodic memory and Pavlovian conditioning: ships passing in the night

https://doi.org/10.1016/j.cobeha.2018.09.019Get rights and content

Highlights

  • Episodic memory and classical conditioning offer distinct insights on emotional memory.

  • We discuss a protocol that synthesizes these historically separated lines of inquiry.

  • Integrating these approaches can advance our understanding of emotional memory.

Research on emotional learning and memory is traditionally approached from one of two directions: episodic memory and classical conditioning. These approaches differ substantially in methodology and intellectual tradition. Here, we offer a new approach to the study of emotional memory in humans that involves integrating theoretical knowledge and experimental techniques from these seemingly distinct fields. Specifically, we describe how subtle modifications to traditional Pavlovian conditioning procedures have provided new insight into how emotional experiences are selectively prioritized in long-term episodic memory. We also speculate on future directions and undeveloped lines of research where some of the knowledge and principles of classical conditioning might advance our understanding of how emotion modifies episodic memory, and vice versa.

Introduction

The ability to remember emotional events can adaptively guide behavior in future situations. Consequently, memory systems are biased to remember experiences encoded around the time of heightened emotional arousal, referred to as the emotional enhancement of memory. This prioritization of emotional memory is adaptive insofar as it helps ensure that we remember people, places, stimuli, situations, and responses associated with important experiences. Research on emotional memory tends to fall into two largely isolated psychological disciplines with characteristically distinct academic traditions: episodic memory and classical (Pavlovian) conditioning. Emotional episodic memory research is generally concerned with explicitly stated knowledge of details surrounding an emotional experience. It is dominated by research on humans, but informed by a history of non-human animal research focused on hippocampal-dependent learning, such as spatial navigation and object recognition. Classical conditioning, on the other hand, describes both a learning process and an experimental procedure by which animals associate neutral stimuli in the environment with meaningful outcomes (e.g. aversive shock or appetitive reward). Neurobiological research on conditioning is predominately focused on the amygdala for its role in learning, storage, and retrieval of threat memories. The goal of this article is to bring into focus the correspondence between these traditionally separated areas of emotional memory research. We briefly describe how ‘emotional memory’ is experimentally defined in episodic memory and conditioning research, describe challenges to studying emotional memory for each field, and discuss how integrating these areas of research can advance our understanding of emotional learning and memory.

Section snippets

Episodic memory and the trouble with isolating the role of emotion

Episodic memory refers to knowledge of the time, place, or other contextual details of an experience [1]. Research on human episodic memory dates back to at least the late nineteenth century [2, 3, 4], and has typically involved testing people’s ability to explicitly recall or recognize a variety of stimuli (words, images, etc.) or the associations between stimuli. Among the most widely replicated findings in episodic memory research is that emotional events are better remembered with more

Pavlovian conditioning and the trouble of isolating individual learning experiences

Conditioning refers to both a learning process and an experimental procedure by which neutral conditional stimuli (CS) acquire the capacity to elicit learned behavioral conditional responses (CR) via association with a biologically salient unconditional stimulus (US). It is traditionally considered an implicit (non-declarative) form of memory mostly unconnected to declarative memory processes [26] (Figure 1). The dominant conditioning paradigm is threat conditioning. Threat conditioning has

Charting the overlap between episodic memory and Pavlovian conditioning

Because human conditioning research is overwhelmingly informed by cue and context conditioning research in rodents, it is generally unconcerned with declarative memory processes. Likewise, because human episodic memory research is generally concerned with higher-order cognitive functions, it is generally unconcerned with putatively reflexive non-declarative memory systems. Indeed, even in the realm of human fear conditioning these forms of memory are typically viewed as operating independently;

Conclusions and future directions

Here we discussed how synthesizing elements of episodic memory and classical conditioning provides unique insight into the mechanisms of emotional memory. A ‘category conditioning’ paradigm allows neutral stimuli to be ‘tagged’ by emotional experiences before, during, or after learning to study the effects on the prioritization into long-term episodic memory that circumvents many of the confounds that have historically affected the field of emotional episodic memory [14••]. At the same time,

Conflict of interest statement

Nothing declared.

References and recommended reading

Papers of particular interest, published within the period of review, have been highlighted as:

  • • of special interest

  • •• of outstanding interest

Acknowledgments

The authors acknowledge funding from NIH R00 MH106719 to J.E.D., and an H2020 Marie Sklodowska-Curie fellowship and a Branco Weiss fellowship - Society in Science to M.C.W.K.

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      Episodic memory is part of declarative or explicit long-term memory, for which the hippocampus and prefrontal cortex are critically involved in encoding, consolidation and retrieval (Dunsmoor and Kroes, 2019; Moscovitch et al., 2016). Additionally, the amygdala is engaged in episodic memories encompassing emotional content, making them quite comparable with memories established by fear conditioning paradigms (Dunsmoor and Kroes, 2019). What we know about the effects of stress hormones on those learning and memory processes involved in fear and anxiety is mainly based on fear conditioning research.

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