Reduced autobiographical memory specificity relates to weak resistance to proactive interference

ErbB4 in parvalbumin-positive interneurons mediates proactive interference in olfactory associative reversal learning

Consolidated memories influence later learning and cognitive processes when new information is overlapped with previous events. To reveal which cellular and molecular factors are associated with this proactive interference, we challenged mice with odor-reward associative learning followed by a reversal-learning task. The results showed that genetical ablation of ErbB4 in parvalbumin (PV)-positive interneurons improved performance in reversal-learning phase, with no alteration in learning phase, supporting that PV interneuron ErbB4 is required for proactive interference. Mechanistically, olfactory learning promoted PV interneuron excitatory synaptic plasticity and direct binding of ErbB4 with presynaptic Neurexin1β (NRXN1β) and postsynaptic scaffold PSD-95 in the prefrontal cortex. Interrupting ErbB4-NRXN1β interaction impaired network activity-driven excitatory inputs and excitatory synaptic transmission onto PV interneurons. Neuronal activity-induced ErbB4-PSD-95 association facilitated transsynaptic binding of ErbB4-NRXN1β and excitatory synapse formation in ErbB4-positive interneurons. Furthermore, ErbB4-NRXN1β binding was responsible for the activity-regulated activation of ErbB4 and extracellular signal-regulated kinase (ERK) 1/2 in PV interneurons, as well as synaptic plasticity-related expression of brain-derived neurotrophic factor (BDNF). Correlatedly, blocking ErbB4-NRXN1β coupling in the medial prefrontal cortex of adult mice facilitated reversal learning of an olfactory associative task. These findings provide novel insight into the physiological role of PV interneuron ErbB4 signaling in cognitive processes and reveal an associative learning-related transsynaptic NRXN1β-ErbB4-PSD-95 complex that affects the ERK1/2-BDNF pathway and underlies local inhibitory circuit plasticity and proactive interference.

The prevalence of intrusive memories in adult depression: A meta-analysis

BACKGROUND

Intrusive memories have typically been associated with post-traumatic stress disorder (PTSD) but some studies have suggested they can also occur in depression-alone.

OBJECTIVE

This meta-analysis aimed to estimate the prevalence of intrusive memories in adult depression and to explore methodological and other factors that may moderate this prevalence.

METHOD

The databases PsycINFO, PsycARTICLES, MedLine, PubMed, CINAHL and Embase were searched for relevant articles, published up to and including July 2016. Studies measuring point prevalence of intrusive memories in adults aged 18 years or above with depression were included and assessed for quality. Meta-analysis was completed under a random effects model.

RESULTS

Seven studies measuring point prevalence of intrusive memories in adult depression were included. The overall pooled prevalence estimate calculated was 76.0% (95% CI 59.4-89.4%), reducing to 66.0% (95% CI 51.0-79.5%) when restricted to intrusive memories experienced within the week prior to assessment. Heterogeneity was high. Between-groups analyses indicated that adults with depression are as likely to experience intrusive memories as adults with PTSD, and more likely to experience intrusive memories than healthy controls (risk ratio of 2.94, 95% CI 1.53-5.67).

LIMITATIONS

The strength of conclusions is limited by the small number of studies included. Consideration of the relationship between depression, intrusive memories and trauma exposure is required.

CONCLUSIONS

Intrusive memories are experienced by a large majority of adults with depression and may therefore be an important target for cognitive intervention. Larger scale measurement of clinical outcome is needed with identification of individual factors predicting treatment response.

Differential roles of resistance to proactive interference and suppression of prepotent responses in overgeneral memory

BACKGROUND AND OBJECTIVES

Overgeneral memory (OGM), difficulty in retrieving specific autobiographical memories, is a robust phenomenon related to the onset and course of depressive and posttraumatic stress disorders. Inhibitory mechanisms are theorized to underlie OGM; however, empirical support for this link is equivocal. The current study examines the differential roles of two aspects of inhibitory control in association with OGM: suppression of prepotent responses and resistance to proactive interference (PI). Only resistance to PI was expected to be negatively related to OGM, whereby individuals with greater ability to resist PI would have reduced OGM.

METHOD

Participants (n = 49) completed a self-report measure of depressive symptoms and engaged in two tasks aimed at assessing resistance to PI and suppression of prepotent responses. Participants also completed a task assessing overgeneral autobiographical memory.

RESULTS

As hypothesized, resistance to PI, but not suppression of prepotent responses negatively predicted OGM above and beyond the influence of depressive symptoms.

LIMITATIONS

Because a double dissociation was not examined, we cannot address the potential independence of the submechanisms of inhibitory control that we assessed.

CONCLUSIONS

Results exemplify the differential associations of two components of inhibition and OGM, suggesting that resistance to PI, in particular, may contribute to the development and/or maintenance of OGM and associated depressive disorders. Directions for future research are discussed.

Lost in distractors: Reduced Autobiographical Memory Specificity and dispersed activation spreading over distractors in working memory

Studies on autobiographical memory retrieval highlight the prominence of rapid and direct access to a specific event memory. Because it has been believed that autobiographical memory retrieval mostly relies on an effortful generative process, there is little empirical evidence on the early stage of information processing that contributes to autobiographical memory specificity (AMS). Therefore, we investigated the associations between AMS and automatic activation of information stimulated by rapid presentation of emotional words. Study 1 involved a visual search task to assess activation of various distractors in working memory. Participants with reduced AMS showed a tendency to activate distractors that were not semantically associated with preceding cues. In Study 2, we manipulated the levels of AMS by using a computerized version of Memory Specificity Training (c-MeST) to observe the changes in the activation of distractors. Results showed that increases in AMS were associated with decreases in activation of cue-unassociated distractors. These findings suggest that reduced AMS can be characterized by dispersed activation spreading over semantically unassociated distractors in automatic information selection of working memory. Because we also found an association between depressive symptoms and AMS, the role of automatic information processing in the relation between reduced AMS and depression is discussed.

Neurobiology of Anorexia Nervosa: Serotonin Dysfunctions Link Self-Starvation with Body Image Disturbances through an Impaired Body Memory

The etiology of anorexia nervosa (AN) is still unclear, despite that it is a critical and potentially mortal illness. A recent neurobiological model considers AN as the outcome of dysfunctions in the neuronal processes related to appetite and emotionality (Kaye et al., 2009, 2013). However, this model still is not able to answer a critical question: What is behind body image disturbances (BIDs) in AN? The article starts its analysis from reviewing some of the studies exploring the effects of the serotonin systems in memory (episodic, working, and spatial) and its dysfunctions. The review suggests that serotonin disturbances may: (a) facilitate the encoding of third person (allocentric) episodic memories; (b) facilitate the consolidation of emotional episodic memories (e.g., teasing), if preceded by repeated stress; (c) reduce voluntary inhibition of mnestic contents; (d) impair allocentric spatial memory. If we discuss these results within the interpretative frame suggested by the “Allocentric Lock Hypothesis” (Riva, 2012, 2014), we can hypothesize that altered serotoninergic activity in AN patients: (i) improves their ability to store and consolidate negative autobiographical memories, including those of their body, in allocentric perspective; (ii) impairs their ability to trigger voluntary inhibition of the previously stored negative memory of the body; (iii) impairs their capacity to retrieve/update allocentric information. Taken together, these points suggest a possible link between serotonin dysfunctions, memory impairments and BIDs: the impossibility of updating a disturbed body memory using real time experiential data—I'm locked to a wrong body stored in long term memory—pushes AN patients to control body weight and shape even when underweight.