Improving mental health by training the suppression of unwanted thoughts

Neurobiology and systems biology of stress resilience

Stress resilience is the phenomenon that some people maintain their mental health despite exposure to adversity or show only temporary impairments followed by quick recovery. Resilience research attempts to unravel the factors and mechanisms that make resilience possible and to harness its insights for the development of preventative interventions in individuals at risk for acquiring stress-related dysfunctions. Biological resilience research has been lagging behind the psychological and social sciences but has seen a massive surge in recent years. At the same time, progress in this field has been hampered by methodological challenges related to finding suitable operationalizations and study designs, replicating findings, and modeling resilience in animals. We embed a review of behavioral, neuroimaging, neurobiological, and systems biological findings in adults in a critical methods discussion. We find preliminary evidence that hippocampus-based pattern separation and prefrontal-based cognitive control functions protect against the development of pathological fears in the aftermath of singular, event-type stressors [as found in fear-related disorders, including simpler forms of posttraumatic stress disorder (PTSD)] by facilitating the perception of safety. Reward system-based pursuit and savoring of positive reinforcers appear to protect against the development of more generalized dysfunctions of the anxious-depressive spectrum resulting from more severe or longer-lasting stressors (as in depression, generalized or comorbid anxiety, or severe PTSD). Links between preserved functioning of these neural systems under stress and neuroplasticity, immunoregulation, gut microbiome composition, and integrity of the gut barrier and the blood-brain barrier are beginning to emerge. On this basis, avenues for biological interventions are pointed out.

Memory control immediately improves unpleasant emotions associated with autobiographical memories of past immoral actions

The ability to stop unwanted memories from coming to mind is theorised to be essential for maintaining good mental health. People can employ intentional strategies to prevent conscious intrusions of negative memories, and repeated attempts to stop retrieval both reduces the frequency of intrusions and improves subsequent emotions elicited by those memories. However, it is still unknown whether memory control can improve negative emotions immediately, at the time control is attempted. It is also not clear which strategy is most beneficial for emotion regulation; clearing the mind of any thoughts of negative memories via direct suppression, or substituting memory recall with alternative thoughts. Here, we provide novel evidence that memory control immediately regulates negative emotions associated with autobiographical memories of morally wrong actions. Repeated control significantly improved negative emotions over time, regardless of the strategy used to implement control. Thought substitution involving either positive diversionary thinking or counterfactual thinking both induced positive feelings, whereas direct suppression neutralised emotions, regardless of whether memories were positive or negative. These empirical findings have implications for clinical practice as they indicate that memory control strategies could be effective emotion regulation methods for real-world intrusive memories.

Everything you ever wanted to know about the Think/No-Think task, but forgot to ask

The Think/No-Think (TNT) task has just celebrated 20 years since its inception, and its use has been growing as a tool to investigate the mechanisms underlying memory control and its neural underpinnings. Here, we present a theoretical and practical guide for designing, implementing, and running TNT studies. For this purpose, we provide a step-by-step description of the structure of the TNT task, methodological choices that can be made, parameters that can be chosen, instruments available, aspects to be aware of, systematic information about how to run a study and analyze the data. Importantly, we provide a TNT training package (as Supplementary Material), that is, a series of multimedia materials (e.g., tutorial videos, informative HTML pages, MATLAB code to run experiments, questionnaires, scoring sheets, etc.) to complement this method paper and facilitate a deeper understanding of the TNT task, its rationale, and how to set it up in practice. Given the recent discussion about the replication crisis in the behavioral sciences, we hope that this contribution will increase standardization, reliability, and replicability across laboratories.

Amnesia in healthy people via hippocampal inhibition: A new forgetting mechanism

Structural damage to the hippocampus gives rise to a severe memory deficit for personal experiences known as organic amnesia. Remarkably, such structural damage may not be the only way of creating amnesia; windows of amnesia can also arise when people deliberately disengage from memory via a process known as retrieval suppression. In this review, we discuss how retrieval suppression induces systemic inhibition of the hippocampus, creating "amnesic shadow" intervals in people's memory for their personal experiences. When new memories are encoded or older memories are reactivated during this amnesic shadow, these memories are disrupted, and such disruption even arises when older memories are subliminally cued. Evidence suggests that the systemic inhibition of the hippocampus during retrieval suppression that gives rise to the amnesic shadow may be mediated by engagement of hippocampal GABAergic inhibitory interneurons. Similar amnesic shadow effects are observed during working memory tasks like the n-back, which also induce notable hippocampal downregulation. We discuss our recent proposal that cognitive operations that require the disengagement of memory retrieval, such as retrieval suppression, are capable of mnemonic process inhibition (the inhibition of mnemonic processes such as encoding, consolidation, and retrieval and not simply individual memories). We suggest that people engage mnemonic process inhibition whenever they shift attention from internal processes to demanding perceptual-motor tasks that may otherwise be disrupted by distraction from our inner world. This hitherto unstudied model of inhibition is a missing step in understanding what happens when attentional shifts occur between internally and externally oriented processes to facilitate goal-directed behaviour. This process constitutes an important novel mechanism underlying the forgetting of life events.

How do the sleep features that characterise depression impact memory?

Depression is associated with general sleep disturbance and abnormalities in sleep physiology. For example, compared with control subjects, depressed patients exhibit lower sleep efficiency, longer rapid eye movement (REM) sleep duration, and diminished slow-wave activity during non-REM sleep. A separate literature indicates that depression is also associated with many distinguishing memory characteristics, including emotional memory bias, overgeneral autobiographical memory, and impaired memory suppression. The sleep and memory features that hallmark depression may both contribute to the onset and maintenance of the disorder. Despite our rapidly growing understanding of the intimate relationship between sleep and memory, our comprehension of how sleep and memory interact in the aetiology of depression remains poor. In this narrative review, we consider how the sleep signatures of depression could contribute to the accompanying memory characteristics.