Directed forgetting in post-traumatic-stress-disorder: a study of refugee immigrants in Germany

The influence of the BDNF Val66Met genotype on emotional recognition memory in post-traumatic stress disorder

Dysregulated consolidation of emotional memories is a core feature of posttraumatic stress disorder (PTSD). Brain Derived Neurotrophic Factor (BDNF) influences synaptic plasticity and emotional memory consolidation. The BDNF Val66Met polymorphism has been associated with PTSD risk and memory deficits respectively, although findings have been inconsistent, potentially due to a failure to control for important confounds such as sex, ethnicity, and the timing/extent of previous trauma experiences. Furthermore, very little research has examined the impact of BDNF genotypes on emotional memory in PTSD populations. This study investigated the interaction effects of Val66Met and PTSD symptomatology in an emotional recognition memory task in 234 participants divided into healthy control (n = 85), trauma exposed (TE: n = 105) and PTSD (n = 44) groups. Key findings revealed impaired negative recognition memory in PTSD compared to control and TE groups and in participants with the Val/Met compared to the Val/Val genotype. There was a group × genotype interaction showing no Met effect in the TE group despite significant effects in PTSD and controls. Results suggest that people previously exposed to trauma who do not develop PTSD may be protected from the BDNF Met effect, however more research is needed to replicate findings and to explore the epigenetic and neural processes involved.

Forgetting Unwanted Memories: Active Forgetting and Implications for the Development of Psychological Disorders

Intrusive memories are a common feature of many psychopathologies, and suppression-induced forgetting of unwanted memories appears as a critical ability to preserve mental health. In recent years, biological and cognitive studies converged in revealing that forgetting is due to active processes. Recent neurobiological studies provide evidence on the active role of main neurotransmitter systems in forgetting, suggesting that the brain actively works to suppress retrieval of unwanted memories. On the cognitive side, there is evidence that voluntary and involuntary processes (here termed "intentional" and "incidental" forgetting, respectively) contribute to active forgetting. In intentional forgetting, an inhibitory control mechanism suppresses awareness of unwanted memories at encoding or retrieval. In incidental forgetting, retrieval practice of some memories involuntarily suppresses the retrieval of other related memories. In this review we describe recent findings on deficits in active forgetting observed in psychopathologies, like post-traumatic stress disorder, depression, schizophrenia, and obsessive-compulsive disorder. Moreover, we report studies in which the role of neurotransmitter systems, known to be involved in the pathogenesis of mental disorders, has been investigated in active forgetting paradigms. The possibility that biological and cognitive mechanisms of active forgetting could be considered as hallmarks of the early onset of psychopathologies is also discussed.

What can directed forgetting tell us about clinical populations?

This paper reviews and critically assesses the implications of directed forgetting (DF) research on clinical populations. We begin by reviewing the typical methods and results of the item method and list method directed forgetting procedures and provide best practice recommendations for future studies using clinical populations. Next, we note that DF was often interpreted as being due to inhibition, and when clinical populations showed impaired directed forgetting, it was treated as evidence in inhibitory control difficulties. However, inhibition may not be the cause of DF effects, based on current understanding of these cognitive tasks. We instead suggest that item method DF is tied to attentional control, which might include inhibitory mechanisms (or might not). In contrast, list method DF is tied to two forms of memory control: control of mental context (indicated by effective forgetting of List 1), and changes in the strategies used to remember (indicated by better learning of List 2). We review the current state of the clinical DF literature, assess its strength based on our best practice recommendations, and call for more research when warranted.

Directed forgetting of emotionally valenced faces

An item-method directed forgetting task was used in three studies to present photographs of happy, neutral and sad faces to participants who had been induced to adopt a happy, neutral or sad mood. At test remember, forget or new judgments of old and new photographs of happy, neutral or sad faces were collected. According to the affect-as-cognitive-feedback hypothesis positively valenced stimuli serve as 'go signals' validating the use of currently accessible cognitions to process task demands whereas negatively valenced stimuli serve as 'stop signals' inhibiting or reversing the use of those cognitions. Since directed forgetting tasks entail the cognitions (among others) that some stimuli should be remembered and others should be forgotten, happy faces should facilitate task demands whereas sad faces should not. As predicted, directed forgetting effects were found for happy but not sad faces in Experiments 1 and 3, and directed forgetting effects were found neutral valenced faces in Experiment 2. Across all three studies mood state did not influence directed forgetting. Findings are discussed in terms of the effects of facial valence cues on directed forgetting and some directions for future research.

Emotional Memory in Post-traumatic Stress Disorder: A Systematic PRISMA Review of Controlled Studies

Background: Emotional memory is an adaptive process that improves the memorization of emotional events or stimuli. In Post-Traumatic Stress Disorder (PTSD), emotional memory may be altered, which in turn may affect symptoms. Having a clearer view of the processes of interaction between memory and emotional stimuli in PTSD may improve our knowledge of this disorder, and could create new therapeutic management tools. Thus, we performed a systematic review of the evidence of specific emotional memory in PTSD patients.

Method: Following PRISMA guidelines, a systematic review of MEDLINE, PsycInfo, and ScienceDirect was undertaken to identify controlled studies on emotional memory that used cognitive tasks on PTSD patients. The initial research was conducted from June 2017 to July 2017, and search terms included: Post-Traumatic Stress Disorder; PTSD; emotional memory; emotion; emotional; memory; and episodic memory.

Results: Eighteen studies reporting on 387 PTSD patients met the eligibility criteria. Among the studies selected, 11 observed specific memory processing in PTSD patients, such as a greater memorization of negative information, or a trend to false recognition of negative information. In addition, attentional and inhibition processing seem to play an important role in emotional memory in PTSD sufferers. Furthermore, other studies that did not find behavioral differences between PTSD and control groups nevertheless showed differences in both specific cerebral activities and neurohormone levels during emotional memory tasks.

Conclusion: This review has several limitations, including a limited number of controlled studies, small sample sizes, different tasks and methods. Nevertheless, the results of this systematic review provide interesting information on emotional memory for clinicians and researchers, as they seem to highlight facilitated memory processing for negative information in PTSD patients. This topic needs further controlled studies with sensitive behavioral tasks. Also, future studies may evaluate emotional memory after symptom amelioration.

The Influence of Trauma on Autobiographical Memory in the Assessment of Somatoform Disorders According to DSM IV Criteria

Recalling an event impairs an individual's later ability to recall related knowledge. Impairment in this retrieval-induced forgetting (RIF) produces a dysfunction in autobiographical memory. This, like somatic symptoms, has been documented in trauma and sexual abuse survivors. To investigate the relationship between past trauma and somatoform disorders, and the role of memory recall dysfunction in this relationship, three sex-matched groups were constituted using DSM IV criteria: Somatoform (SD) (n. 22) other Psychiatric Disorders (PD) (n. 26) and Healthy Subjects (HS) (n. 35). Responses to Stressful Life Events Screening Questionnaire revised (SLESQ-R); Direct Forgetting paradigm (DF) for autobiographical memory; Deese-Roediger-McDermott (DRM) paradigm for false memory; Stanford Scale type A for Post-Hypnotic Amnesia (PHA); Stroop Colour Word test and a digit-span for cognitive assessment; and Somatosensory Amplification Scale (SSAS), Somatic Dissociation Questionnaire (SDQ-20), and Toronto Alexithymia Scale (TAS 20) for somatic discomfort were compared among groups. SSAS, SDQ-20 and TAS F1 were correlated with SLESQ-R scores; subjects with higher numbers of traumatic events (NSE) showed greater capacity to remember items-to-be-forgotten (DFF) and higher SDQ-20 scores. Although the SD group showed higher NSE, their autobiographical memory scores were no different to those of other DSM-IV groups. The somatic-trauma-autobiographical memory impairment relationship is identified by DSM V but not DSM IV criteria for somatoform disorder. Higher NSE appears to correlate with both the presence of somatic discomfort and impaired autobiographical memory, suggesting autonoetic consciousness dysfunction in subjects with past trauma and current somatic symptom disorders.

Neurocognitive and Information Processing Biases in Posttraumatic Stress Disorder

PURPOSE OF REVIEW

We review recent research addressing neurocognitive and information processing abnormalities in posttraumatic stress disorder (PTSD), including studies informing direction of causality. We additionally consider neurocognition in the context of co-morbid mild traumatic brain injury (TBI) and psychosocial treatments for PTSD.

RECENT FINDINGS

Learning, memory, attention, inhibitory functions, and information processing biases frequently accompany PTSD, reflecting potential bi-directional relationships with PTSD. Although mild TBI is associated with increased risk of PTSD development and maintenance, TBI does not typically contribute significantly to sustained neurocognitive deficits in individuals with PTSD. Whereas better learning and memory is associated with mildly enhanced response to psychosocial interventions, such interventions may also improve neurocognitive performance and can be effectively provided to patients with TBI history. PTSD is associated with cognitive abnormalities in processing both emotionally relevant and emotionally neutral information and, although mild, may underlie some PTSD symptom expression.

Lethal hopelessness: Understanding and responding to asylum seeker distress and mental deterioration

The mental deterioration of the so called 'legacy caseload' (asylum seekers who arrived in Australia by boat between August 2012-December 2013) has become a national concern and is garnering international attention. Prolonged uncertainty is contributing to mental deterioration and despair. There have been at least 11 deaths by suicide since June 2014. Social support services have been limited and legal assistance in short supply; this is associated with lengthy delays with visa applications. Thwarted belongingness, purpose and identity, a shortage of available services, and barriers to legal support for processes attendant upon Refugee Status Determination increase the likelihood that the mental health of asylum seekers will deteriorate further, potentially developing into worsening decline, which will lead to increased self-harm and suicide. This article summarises recent suicide deaths in Australia, positing practical assistance and support for asylum seekers living in the community. Therapeutic engagement should be trauma-informed wherever possible, helping asylum seekers to reframe their sense of lethal hopelessness.

Weak evidence for increased motivated forgetting of trauma-related words in dissociated or traumatised individuals in a directed forgetting experiment

Motivated forgetting is the idea that people can block out, or forget, upsetting or traumatic memories, because there is a motivation to do so. Some researchers have cited directed forgetting studies using trauma-related words as evidence for the theory of motivated forgetting of trauma. In the current article subjects used the list method directed forgetting paradigm with both trauma-related words and positive words. After one list of words was presented subjects were directed to forget the words previously learned, and they then received another list of words. Each list was a mix of positive and trauma-related words, and the lists were counterbalanced. Later, subjects recalled as many of the words as they could, including the ones they were told to forget. Based on the theory that motivated forgetting would lead to recall deficits of trauma-related material, we created eight hypotheses. High dissociators, trauma-exposed, sexual trauma-exposed, and high dissociators with trauma-exposure participants were hypothesised to show enhanced forgetting of trauma words. Results indicated only one of eight hypotheses was supported: those higher on dissociation and trauma recalled fewer trauma words in the to-be-forgotten condition, compared to those low on dissociation and trauma. These results provide weak support for differential motivated forgetting.

Are Hallucinations Due to an Imbalance Between Excitatory and Inhibitory Influences on the Brain?

This review from the International Consortium on Hallucinations Research intends to question the pertinence of the excitatory-to-inhibitory (E/I) imbalance hypothesis as a model for hallucinations. A large number of studies suggest that subtle impairments of the E/I balance are involved in neurological and psychiatric conditions, such as schizophrenia. Emerging evidence also points to a role of the E/I balance in maintaining stable perceptual representations, suggesting it may be a plausible model for hallucinations. In support, hallucinations have been linked to inhibitory deficits as shown with impairment of gamma-aminobutyric acid transmission, N-methyl-d-aspartate receptor plasticity, reductions in gamma-frequency oscillations, hyperactivity in sensory cortices, and cognitive inhibition deficits. However, the mechanisms by which E/I dysfunctions at the cellular level might relate to clinical symptoms and cognitive deficits remain unclear. Given recent data advances in the field of clinical neuroscience, it is now possible to conduct a synthesis of available data specifically related to hallucinations. These findings are integrated with the latest computational frameworks of hallucinations, and recommendations for future research are provided.

'Forget me (not)?' - Remembering Forget-Items Versus Un-Cued Items in Directed Forgetting

Humans need to be able to selectively control their memories. This capability is often investigated in directed forgetting (DF) paradigms. In item-method DF, individual items are presented and each is followed by either a forget- or remember-instruction. On a surprise test of all items, memory is then worse for to-be-forgotten items (TBF) compared to to-be-remembered items (TBR). This is thought to result mainly from selective rehearsal of TBR, although inhibitory mechanisms also appear to be recruited by this paradigm. Here, we investigate whether the mnemonic consequences of a forget instruction differ from the ones of incidental encoding, where items are presented without a specific memory instruction. Four experiments were conducted where un-cued items (UI) were interspersed and recognition performance was compared between TBR, TBF, and UI stimuli. Accuracy was encouraged via a performance-dependent monetary bonus. Experiments varied the number of items and their presentation speed and used either letter-cues or symbolic cues. Across all experiments, including perceptually fully counterbalanced variants, memory accuracy for TBF was reduced compared to TBR, but better than for UI. Moreover, participants made consistently fewer false alarms and used a very conservative response criterion when responding to TBF stimuli. Thus, the F-cue results in active processing and reduces false alarm rate, but this does not impair recognition memory beyond an un-cued baseline condition, where only incidental encoding occurs. Theoretical implications of these findings are discussed.