Back to the future: Progressing memory research in eating disorders

Abstract

Objective: Human behaviors, thoughts, and emotions are guided by memories of the past. Thus, there can be little doubt that memory plays a fundamental role in the behaviors (e.g., binging), thoughts (e.g., body-image concerns), and emotions (e.g., guilt) that characterize eating disorders (EDs). Although a growing body of research has begun to investigate the role of memory in EDs, this literature is limited in numerous ways and has yet to be integrated into an overarching framework.

Methods: In the present article, we provide an operational framework for characterizing different domains of memory, briefly review existing ED memory research within this framework, and highlight crucial gaps in the literature.

Results: We distinguish between three domains of memory-episodic, procedural, and working-which differ based on functional attributes and underlying neural systems. Most recent ED memory research has focused on procedural memory broadly defined (e.g., reinforcement learning), and findings within all three memory domains are highly mixed. Further, few studies have attempted to assess these different domains simultaneously, though most behavior is achieved through coordination and competition between memory systems. We, therefore, offer recommendations for how to move ED research forward within each domain of memory and how to study the interactions between memory systems, using illustrative examples from other areas of basic and clinical research.

Discussion: A stronger and more integrated understanding of the mechanisms that connect memory of past experiences to present ED behavior may yield more comprehensive theoretical models of EDs that guide novel treatment approaches.

Public significance: Memories of previous eating-related experiences may contribute to the onset and maintenance of eating disorders (EDs). However, research on the role of memory in EDs is limited, and distinct domains of ED memory research are rarely connected. We, therefore, offer a framework for organizing, progressing, and integrating ED memory research, to provide a better foundation for improving ED treatment and intervention going forward.

Keywords: anorexia; associative learning; binge-eating; bulimia; eating disorders; episodic memory; learning; memory; procedural memory; working memory.

FIGURE 1

Contrasting three broad domains of memory. Key features (left) and typical methods for testing (right) three domains of memory. This operational framework for distinguishing memory domains is based on differences in functional attributes and underlying neural systems (Henke, 2010; Howard & Cohen, 2004; Tulving, 2007), but its definitions here are broad for the sake of organizational clarity. Note that memory encoding refers to the representation of information so that it has the potential to influence thought and behavior in the future (i.e., memory creation). Memory retrieval refers to the processes that allow previously encoded information to influence thoughts or behavior in the present. In the procedural memory panel, the apple/airplane with a bar over it represents the average (i.e., generalized) value of the item.

FIGURE 2

Neuroanatomy of memory domains. A given brain region may contribute to multiple memory systems. However, episodic, procedural, and working memory depend on somewhat anatomically distinct networks (Rottschy et al., 2012; Sherman et al., 2023). Working memory is reliant upon inferior, superior, and medial frontal regions, parietal and insular cortices, and the thalamus (regions in red). Procedural memory function is supported by the dorsal striatum (regions in green), whilst episodic memory relies upon medial temporal lobe structures, including the hippocampus, parahippocampal gyrus, and entorhinal cortex (regions in blue). Given the fairly distinct anatomical systems supporting different types of memory, neuroimaging approaches (e.g., fMRI, MEG, and EEG), may be useful in elucidating the particular memory alterations that exist in EDs, as well as indicating targets of interventions to address these alterations.

FIGURE 3

Examples for progressing research on each domain of memory separately. (a) Episodic item memory (for the cupcake) may be successful, while relational memory for the context the item was encountered in can be specific (beach on left), general (beach on right), or failed (forest) (Goldfarb et al., 2020). (b) Procedural memory can be influenced by cognitive or affective states. For example, a ruminative state can impair procedural memory and thus potentially impair adaptive behavior (Hitchcock, Fried, & Frank, 2022). (c) Working memory is useful not only when it maintains information important to current goals (items in top row), but also when it successfully filters out information that is irrelevant to current goals (food items on bottom row) (Stout et al., 2015).

FIGURE 4

Examples of dissociating memory subprocesses. (a) Multiple processes during encoding, storage, and/or retrieval could influence episodic relational memory. One simple mechanism could be imbalanced attention (i.e., to disorder-relevant cues) during encoding. This could be tested by varying the timing and order in which related information is encoded (Forester & Kamp, 2023). (b) Alterations in reward-based procedural memory could reflect differences in, for example, reward sensitivity or the ability to incrementally abstract statistical information (e.g., the relative probabilities of living and non-living objects). In this task, individuals especially sensitive to reward may be inappropriately biased by incidental associations with reward, while learning normally in a context without rewards (McGuire et al., 2014). (c) Working memory problems could occur, for example, due to impaired storage of task-relevant information or a failure to control access to working memory during either encoding or retrieval (see Figure 3c). But, it could also be due to an inability to remove no-longer-relevant information from working memory during storage (Lewis-Peacock et al., 2018).

FIGURE 5

Examples of integrative assessments of memory across memory domains. (a) Simplified task design to study the joint influence of procedural and working memory on decision making. The high working-memory load condition includes a greater number of unique stimuli, and more time in between repetitions, which taxes working memory. Based on procedural memory alone, however, the choice should be the same, because the average reward value for the apple/airplane is the same in both conditions. Differences in choice may therefore reflect the influence of working memory (Collins et al., 2014). (b) Simplified task design to study the joint influence of procedural and episodic memory on decision making. At the time of retrieval, procedural and episodic memory may have different preferences: procedural memory should favor the novel red object because red has recently been more rewarding (incremental generalization), while episodic memory might favor the ant because the ant was previously associated with a high reward (single instance detail). When certainty is low (due to volatility in whether red or blue is more rewarding), behavior may be guided more by episodic memory, even if this is maladaptive (Nicholas et al., 2022).