Memory Control: A Fundamental Mechanism of Emotion Regulation

The neural correlates of emotion regulation have been studied extensively over the past decade, but without consideration of the mechanistic role of memory control. Knowledge of the neurocognitive mechanisms enabling the suppression of memories and thoughts from conscious awareness has grown increasingly specific. Recent studies reveal an association between memory control deficits and affective psychopathologies such as depression and post-traumatic stress disorder, suggesting that controlling memory and affect are interrelated. Successfully controlling the retrieval of intrusive memories reduces their later emotional impact via modulation of amygdala activity, indicating that controlling memories regulates affect. Memory control processes may provide a mechanistic foundation for emotion regulation, thereby contributing to a unified account of the mechanisms underlying this process. Memories play a ubiquitous role in our emotional lives, both causing vivid emotional experiences in their own right and imbuing perception of the external world with emotional significance. Controlling the emotional impact of memories therefore poses a major emotion-regulation challenge, suggesting that there might be a hitherto unexplored link between the neurocognitive mechanisms underlying memory control (MC) and emotion regulation. We present here a theoretical account of how the mechanisms of MC constitute core component processes of cognitive emotion regulation (CER), and how this observation may help to understand its basic mechanisms and their disruption in psychiatric disorders. Memories play a ubiquitous role in our emotional lives, both causing vivid emotional experiences in their own right and imbuing perception of the external world with emotional significance. Controlling the emotional impact of memories therefore poses a major emotion-regulation challenge, suggesting that there might be a hitherto unexplored link between the neurocognitive mechanisms underlying memory control (MC) and emotion regulation. We present here a theoretical account of how the mechanisms of MC constitute core component processes of cognitive emotion regulation (CER), and how this observation may help to understand its basic mechanisms and their disruption in psychiatric disorders. Affective science has often sought to explain how external stimuli cause emotional reactions [1Gross J.J. Barrett L.F. Emotion generation and emotion regulation: one or two depends on your point of view.Emot. Rev. 2011; 3: 8-16Crossref PubMed Scopus (193) Google Scholar]. 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Understanding how people regulate exogenously elicited emotions (see Glossary) is, and should be, a fundamental goal of emotion regulation research. However, research on emotion regulation would benefit from a mechanistic understanding of an equally great – perhaps even greater – source of emotional states in our daily lives: memory. Outside the immediate experience of emotional events, any later impact – adaptive or maladaptive – that they have on our lives is mediated by memory. Like Proust's madeleines, the triggers for this are often stimuli that most people would consider innocuous, but that by virtue of evoking an episodic memory in the individual have the power to elicit neural, physiological, and subjective reactions mimicking those of the original experience [6Daselaar S.M. et al.The spatiotemporal dynamics of autobiographical memory: neural correlates of recall, emotional intensity, and reliving.Cereb. 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Despite these illustrations of the important role of memories in shaping our emotional lives, how we regulate emotions by downregulating the memory traces that contribute to them has attracted comparatively little attention in research on emotion regulation. In this Opinion article we outline a view of the mechanisms supporting the regulation of mnemonic emotional material building on emerging findings from research on memory control (MC). Our starting point is the observation that, because our emotions are frequently driven by memories, controlling the accessibility of such memories to awareness should be an effective way of regulating one's emotional reactions [20Anderson M.C. Hanslmayr S. Neural mechanisms of motivated forgetting.Trends Cogn. Sci. 2014; 18: 279-292Abstract Full Text Full Text PDF PubMed Google Scholar]. Nevertheless, various factors have contributed to the view that attempts to voluntarily suppress thoughts and memories are unhelpful, and are perhaps harmful (Box 1). Contrary to this, we claim that controlling the occurrence and/or constitution of an upsetting memory – in short, MC – is the ultimate objective of successful emotion regulation of endogenous materials.Box 1Differentiating Direct Retrieval Suppression from Other Suppressive PhenomenaA potential source of confusion about our argument is the tendency to equate DS with other, often counterproductive, suppressive phenomena. For example, in emotion regulation research 'suppression' usually refers to expressive suppression (ES), which involves inhibiting the behavioral expressions associated with emotional states (e.g., adopting a poker face to hide emotions). Owing to its small or even paradoxical effects on subjective emotion [74Gross J.J. Antecedent- and response-focused emotion regulation: divergent consequences for experience, expression, and physiology.J. Pers. Soc. Psychol. 1998; 74: 224-237Crossref PubMed Google Scholar, 85Goldin P.R. et al.The neural bases of emotion regulation: reappraisal and suppression of negative emotion.Biol. Psychiatry. 2008; 63: 577-586Abstract Full Text Full Text PDF PubMed Scopus (785) Google Scholar], and because the trait tendency to use ES is associated with poor mental health outcomes [86John O.P. Gross J.J. Healthy and unhealthy emotion regulation: personality processes, individual differences, and life span development.J. Pers. 2004; 72: 1301-1333Crossref PubMed Scopus (759) Google Scholar], ES is often considered to be a maladaptive emotion-regulation strategy. However, DS clearly differs from ES in that it directly acts on the representation of the unwanted memory, rendering it less accessible. As such, DS is a fully cognitive strategy, involving different regulatory mechanisms.Another related line of research is thought suppression, as explored through the 'white bear effect'. In this research participants are instructed to not think of a specific item (e.g., a white bear) over a period of 5 minutes, and report when it comes to mind [87Wegner D.M. Schneider D.J. The white bear story.Psychol. Inq. 2003; 14: 326-329Crossref Google Scholar]. Research using this paradigm has shown that participants have difficulty avoiding thinking about the item, and this has been taken to show the inefficacy and counterproductive nature of thought suppression [87Wegner D.M. Schneider D.J. The white bear story.Psychol. Inq. 2003; 14: 326-329Crossref Google Scholar, 88Wegner D.M. et al.Paradoxical effects of thought suppression.J. Pers. Soc. Psychol. 1987; 53: 5-13Crossref PubMed Google Scholar]. While DS conceptually resembles the 'white bear' variety of thought suppression, the experimental procedure used to investigate the latter has characteristics that make suppression inherently unlikely to succeed. Specifically, the white bear task makes explicit reference to a specific forbidden thought to be suppressed. However, achieving this stated goal is effectively impossible because simply remembering the purpose of the task requires that participants violate the task goal. This contrasts with the DS task, which does not integrate the specific memory/thought to be avoided as part of the task goal, rendering retrieval suppression possible. This 'goal-integration theory' may account for the apparent discrepancy between work on MC and the Wegner thought-suppression paradigm [89Anderson M.C. Huddleston E. Towards a cognitive and neurobiological model of motivated forgetting.in: Belli R.F. True and False Recovered Memories. Springer, New York, NY2012: 53-120Crossref Scopus (73) Google Scholar], and suggests that the white bear task might fail to capture the true utility of suppressive processes measured in work on MC. Consistent with this, a meta-analysis [90Magee J.C. et al.Psychopathology and thought suppression: a quantitative review.Clin. Psychol. Rev. 2012; 32: 189-201Crossref PubMed Scopus (0) Google Scholar] of 33 studies of psychopathology using the white bear task found no differences in suppression success or in rebound effects across patients and controls, raising concerns about whether this the task captures the mechanistic deficits that lead to intrusions in real life.Researchers have also investigated the relationship between thought suppression and psychopathology via the white bear suppression inventory (WBSI). Such work has contributed to the widely repeated conclusion that suppression, as a coping strategy, is associated with increased risk of psychopathology [91Aldao A. et al.Emotion-regulation strategies across psychopathology: a meta-analytic review.Clin. Psychol. Rev. 2010; 30: 217-237Crossref PubMed Scopus (1405) Google Scholar]. Although the WBSI was intended to measure tendency to suppress thoughts, large-scale studies have now repeatedly found that the scale measures both the tendency to suppress thoughts and the degree to which they fail at doing so [92Rassin E. The white bear suppression inventory (WBSI) focuses on failing suppression attempts.Eur. J. Pers. 2003; 17: 285-298Crossref Scopus (48) Google Scholar, 93Höping W. de Jong-Meyer R. Differentiating unwanted intrusive thoughts from thought suppression: what does the white bear suppression inventory measure?.Pers. Individ. Dif. 2003; 34: 1049-1055Crossref Scopus (0) Google Scholar, 94Blumberg S.J. The white bear suppression inventory: revisiting its factor structure.Pers. Individ. Dif. 2000; 29: 943-950Crossref Google Scholar]. Importantly, failure at, but not tendency to, suppress thoughts predicts psychopathology. Indeed, when successful thought-control ability is separately quantified [41Catarino A. et al.Failing to forget: inhibitory-control deficits compromise memory suppression in posttraumatic stress disorder.Psychol. Sci. 2015; 26: 604-616Crossref PubMed Scopus (34) Google Scholar] it robustly predicts reduced symptoms of anxiety, depression, and other conditions characterized by intrusive symptomatology. These findings are consistent with the possibility that, in normative samples, thought suppression may play an important beneficial role in mental health. A potential source of confusion about our argument is the tendency to equate DS with other, often counterproductive, suppressive phenomena. For example, in emotion regulation research 'suppression' usually refers to expressive suppression (ES), which involves inhibiting the behavioral expressions associated with emotional states (e.g., adopting a poker face to hide emotions). Owing to its small or even paradoxical effects on subjective emotion [74Gross J.J. Antecedent- and response-focused emotion regulation: divergent consequences for experience, expression, and physiology.J. Pers. Soc. Psychol. 1998; 74: 224-237Crossref PubMed Google Scholar, 85Goldin P.R. et al.The neural bases of emotion regulation: reappraisal and suppression of negative emotion.Biol. Psychiatry. 2008; 63: 577-586Abstract Full Text Full Text PDF PubMed Scopus (785) Google Scholar], and because the trait tendency to use ES is associated with poor mental health outcomes [86John O.P. Gross J.J. Healthy and unhealthy emotion regulation: personality processes, individual differences, and life span development.J. Pers. 2004; 72: 1301-1333Crossref PubMed Scopus (759) Google Scholar], ES is often considered to be a maladaptive emotion-regulation strategy. However, DS clearly differs from ES in that it directly acts on the representation of the unwanted memory, rendering it less accessible. As such, DS is a fully cognitive strategy, involving different regulatory mechanisms. Another related line of research is thought suppression, as explored through the 'white bear effect'. In this research participants are instructed to not think of a specific item (e.g., a white bear) over a period of 5 minutes, and report when it comes to mind [87Wegner D.M. Schneider D.J. The white bear story.Psychol. Inq. 2003; 14: 326-329Crossref Google Scholar]. Research using this paradigm has shown that participants have difficulty avoiding thinking about the item, and this has been taken to show the inefficacy and counterproductive nature of thought suppression [87Wegner D.M. Schneider D.J. The white bear story.Psychol. Inq. 2003; 14: 326-329Crossref Google Scholar, 88Wegner D.M. et al.Paradoxical effects of thought suppression.J. Pers. Soc. Psychol. 1987; 53: 5-13Crossref PubMed Google Scholar]. While DS conceptually resembles the 'white bear' variety of thought suppression, the experimental procedure used to investigate the latter has characteristics that make suppression inherently unlikely to succeed. Specifically, the white bear task makes explicit reference to a specific forbidden thought to be suppressed. However, achieving this stated goal is effectively impossible because simply remembering the purpose of the task requires that participants violate the task goal. This contrasts with the DS task, which does not integrate the specific memory/thought to be avoided as part of the task goal, rendering retrieval suppression possible. This 'goal-integration theory' may account for the apparent discrepancy between work on MC and the Wegner thought-suppression paradigm [89Anderson M.C. Huddleston E. Towards a cognitive and neurobiological model of motivated forgetting.in: Belli R.F. True and False Recovered Memories. Springer, New York, NY2012: 53-120Crossref Scopus (73) Google Scholar], and suggests that the white bear task might fail to capture the true utility of suppressive processes measured in work on MC. Consistent with this, a meta-analysis [90Magee J.C. et al.Psychopathology and thought suppression: a quantitative review.Clin. Psychol. Rev. 2012; 32: 189-201Crossref PubMed Scopus (0) Google Scholar] of 33 studies of psychopathology using the white bear task found no differences in suppression success or in rebound effects across patients and controls, raising concerns about whether this the task captures the mechanistic deficits that lead to intrusions in real life. Researchers have also investigated the relationship between thought suppression and psychopathology via the white bear suppression inventory (WBSI). Such work has contributed to the widely repeated conclusion that suppression, as a coping strategy, is associated with increased risk of psychopathology [91Aldao A. et al.Emotion-regulation strategies across psychopathology: a meta-analytic review.Clin. Psychol. Rev. 2010; 30: 217-237Crossref PubMed Scopus (1405) Google Scholar]. Although the WBSI was intended to measure tendency to suppress thoughts, large-scale studies have now repeatedly found that the scale measures both the tendency to suppress thoughts and the degree to which they fail at doing so [92Rassin E. The white bear suppression inventory (WBSI) focuses on failing suppression attempts.Eur. J. Pers. 2003; 17: 285-298Crossref Scopus (48) Google Scholar, 93Höping W. de Jong-Meyer R. Differentiating unwanted intrusive thoughts from thought suppression: what does the white bear suppression inventory measure?.Pers. Individ. Dif. 2003; 34: 1049-1055Crossref Scopus (0) Google Scholar, 94Blumberg S.J. The white bear suppression inventory: revisiting its factor structure.Pers. Individ. Dif. 2000; 29: 943-950Crossref Google Scholar]. Importantly, failure at, but not tendency to, suppress thoughts predicts psychopathology. Indeed, when successful thought-control ability is separately quantified [41Catarino A. et al.Failing to forget: inhibitory-control deficits compromise memory suppression in posttraumatic stress disorder.Psychol. Sci. 2015; 26: 604-616Crossref PubMed Scopus (34) Google Scholar] it robustly predicts reduced symptoms of anxiety, depression, and other conditions characterized by intrusive symptomatology. These findings are consistent with the possibility that, in normative samples, thought suppression may play an important beneficial role in mental health. More controversially perhaps, we further propose that MC mechanisms underlie the benefits of many of the volitional cognitive emotion regulation (CER) phenomena that have been identified, even when regulation is targeted at exogenously driven emotional reactions. Specifically, we claim that CER strategies can be classified by whether they employ two core mechanisms of MC that reduce access to memory traces that contribute to emotional responses. Importantly, we propose that the mechanisms of MC offer a novel account of how emotion regulation is implemented, that may help to understand its normal functioning and also psychopathological syndromes. This proposal is motivated by growing evidence that instructed MC abilities are related to beneficial outcomes (reviewed below) and the belief that similar mechanisms may support spontaneous MC, and therefore spontaneous CER, although further research will be necessary to test this assumption. As such, we propose that MC is crucial to regulating both mnemonically and exogenously elicited emotional states, and should be considered to be a fundamental process of volitional emotion regulation. MC can be defined as the capacity to volitionally influence the contents of thought in a goal-directed fashion by reducing the accessibility of memories [20Anderson M.C. Hanslmayr S. Neural mechanisms of motivated forgetting.Trends Cogn. Sci. 2014; 18: 279-292Abstract Full Text Full Text PDF PubMed Google Scholar]. MC is often exerted reactively, in response to reminders that trigger the automatic retrieval of an unwanted memory or thought. Two mechanisms have been identified that enable MC when someone confronts an unwelcome reminder: (i) direct suppression (DS), involving the stopping or cancellation of the episodic retrieval process initiated by the cue, and the inhibition of the unwanted trace, and (ii) thought substitution (TS), involving the engagement of episodic retrieval, but instead being redirected towards alternative memories to occupy the limited focus of awareness, and to inhibit the to-be-avoided memory [20Anderson M.C. Hanslmayr S. Neural mechanisms of motivated forgetting.Trends Cogn. Sci. 2014; 18: 279-292Abstract Full Text Full Text PDF PubMed Google Scholar]. Both of these mechanisms can be voluntarily deployed, and both induce forgetting of unwanted memories [21Küpper C.S. et al.Direct suppression as a mechanism for controlling unpleasant memories in daily life.J. Exp. Psychol. 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The capacity to induce forgetting sets these mechanisms apart from conventional cognitive or behavioral avoidance: MC involves not simply avoiding reminders that trigger unwanted thoughts or memories but instead involves directly confronting those reminders and actively altering our cognitive response to them, and reducing the accessibility of the associated memory trace. DS of retrieval should not be confused with other forms of suppression that are often discussed in research on emotion regulation, and which have been argued to be ineffective and maladaptive (Box 1). Extensive evidence shows that suppressing retrieval in response to reminders is possible, and that doing so has persisting effects on the accessibility of suppressed traces [21Küpper C.S. et al.Direct suppression as a mechanism for controlling unpleasant memories in daily life.J. Exp. Psychol. Gen. 2014; 143: 1443-1449Crossref PubMed Scopus (30) Google Scholar, 25Benoit R.G. Anderson M.C. 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Such reminders are believed to trigger (owing to the affective qualities of the reminder, or of the unwelcome memory) inhibitory control to countermand the retrieval of the associated event, in a manner analogous to the way that control processes countermand motor processes to stop physical actions. Evidence indicates that repeated DS over multiple encounters with a reminder weakens the associated memory until it no longer intrudes [26Gagnepain P. et al.Parallel regulation of memory and emotion supports the suppression of intrusive memories.J. Neurosci. 2017; 37: 6423-6441Crossref PubMed Scopus (6) Google Scholar, 32Benoit R.G. et al.Adaptive top-down suppression of hippocampal activity and the purging of intrusive memories from consciousness.J. Cogn. Neurosci. 2015; 27: 96-111Crossref PubMed Scopus (0) Google Scholar, 36Levy B.J. Anderson M.C. Purging of memories from conscious awareness tracked in the human brain.J. 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