Early life stress explains reduced positive memory biases in remitted depression

"The wrong tools for the right job": a critical meta-analysis of traditional tests to assess behavioural impacts of maternal separation

RATIONALE

Unconditioned tasks in rodents have been the mainstay of behavioural assessment for decades, but their validity and sensitivity to detect the behavioural consequences of early life stress (ELS) remains contentious and highly variable.

OBJECTIVES

In the present study, we carried out a meta-analysis to investigate whether persistent behavioural effects, as assessed using unconditioned procedures in rats, are a reliable consequence of early repeated maternal separation, a commonly used procedure in rodents to study ELS.

METHODS

A literature search identified 100 studies involving maternally separated rats and the following unconditioned procedures: the elevated plus maze (EPM); open field test (OFT); sucrose preference test (SPT) and forced swim task (FST). Studies were included for analysis if the separation of offspring from the dam was at least 60 min every day during the pre-weaning period prior to the start of adolescence.

RESULTS

Our findings show that unconditioned tasks are generally poor at consistently demonstrating differences between control and separated groups with pooled effect sizes that were either small or non-existent (EPM: Hedge's g =  - 0.35, p = 0.01, OFT: Hedge's g =  - 0.32, p = 0.05, SPT: Hedge's g =  - 0.33, p = 0.21, FST: Hedge's g = 0.99, p = 0.0001). Despite considerable procedural variability between studies, heterogeneity statistics were low; indicating the lack of standardization in the maternal separation protocol was the not the cause of these inconsistent effects.

CONCLUSIONS

Our findings indicate that in general, unconditioned tests of depression and anxiety are not sufficient to reveal the full behavioural repertoire of maternal separation stress should not be relied upon in isolation. We argue that more objective tasks that sensitively detect specific cognitive processes are better suited for translational research on stress-related disorders such as depression.

Emotional reactivity and explicit emotional memory biases in major depressive disorder during euthymia

Major depressive disorder (MDD) is associated with information processing deficits across several cognitive domains. Two examples include biased reactivity (e.g., emotional arousal/reaction) to, and explicit (episodic) memory for, emotional information. Recent research suggests that, compared to healthy controls (HCs), acute depressive states may be associated with reduced reactivity to emotional information in the absence of explicit emotional memory biases; however, our understanding of the cognitive phenotypes of these phenomena during euthymia (i.e., clinical remission) remain unclear. Sixty-one participants completed the current study (30 euthymic MDD, 31 matched HCs). Participants rated the emotional intensity (i.e., emotional reactivity) of 48 negative, 48 neutral, and 48 positive images before returning one week later for a surprise recognition memory task. We found main effects of valence across analyses of the emotional reactivity and memory data, such that: (1) both groups displayed higher mean intensity ratings for negative versus positive images (p < 0.0001), for positive versus neutral images (p < 0.0001), and for negative versus neutral images (p < 0.0001); (2) both groups displayed reduced memory sensitivity (e.g., the ability to accurately discriminate between signal (i.e., old stimuli) and noise (i.e., new stimuli) for positive compared to neutral (p = 0.007) and negative (p = 0.03) images; and (3) both groups displayed reduced normalized memory sensitivity for positive versus negative images (p = 0.006). The euthymic MDD group did not differ from the HC group on emotional reactivity or emotional memory performance. These findings contribute to growing evidence that emotional reactivity and explicit emotional memory may not be affected in individuals with MDD during euthymia.

A Pilot Study of Smartphone-Based Memory Bias Modification and Its Effect on Memory Bias and Depressive symptoms in an Unselected Population

Memory bias modification (MBM) is a relatively new approach at targeting biased processing—a central cognitive factor causing and maintaining depression. In this pilot study we aimed to develop a smartphone-based autobiographical memory training, a novel form of MBM. A total of 153 unselected participants were randomly allocated to one of three experimental training conditions (positive, negative or sham memory training) conducted over a period of three days. Autobiographical memory bias and depressive scores were assessed pre- and post-training, whilst recent event recall and explicit self-referent memory bias were assessed post-training. Positive memory bias significantly increased in the positive training condition, however memory bias did not significantly differ post-training between the three conditions. Participants who received positive training recalled a positive autobiographical event more frequently compared to the other conditions. No significant difference between conditions was found in the other outcomes, including symptoms. The novel smartphone-based MBM intervention seems apt to affect autobiographical memory of emotional material. Future research should explore its possible (therapeutic) application.

Blame-rebalance fMRI neurofeedback in major depressive disorder: A randomised proof-of-concept trial

Previously, using fMRI, we demonstrated lower connectivity between right anterior superior temporal (ATL) and anterior subgenual cingulate (SCC) regions while patients with major depressive disorder (MDD) experience guilt. This neural signature was detected despite symptomatic remission which suggested a putative role in vulnerability. This randomised controlled double-blind parallel group clinical trial investigated whether patients with MDD are able to voluntarily modulate this neural signature. To this end, we developed a fMRI neurofeedback software (FRIEND), which measures ATL-SCC coupling and displays its levels in real time. Twenty-eight patients with remitted MDD were randomised to two groups, each receiving one session of fMRI neurofeedback whilst retrieving guilt and indignation/anger-related autobiographical memories. They were instructed to feel the emotion whilst trying to increase the level of a thermometer-like display on a screen. Active intervention group: The thermometer levels increased with increasing levels of ATL-SCC correlations in the guilt condition. Control intervention group: The thermometer levels decreased when correlation levels deviated from the previous baseline level in the guilt condition, thus reinforcing stable correlations. Both groups also received feedback during the indignation condition reinforcing stable correlations. We confirmed our predictions that patients in the active intervention group were indeed able to increase levels of ATL-SCC correlations for guilt vs. indignation and their self-esteem after training compared to before training and that this differed significantly from the control intervention group. These data provide proof-of-concept for a novel treatment target for MDD patients and are in keeping with the hypothesis that ATL-SCC connectivity plays a key role in self-worth.

https://clinicaltrials.gov/ct2/show/results/NCT01920490

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Employs real-time fMRI of anterior temporal –subgenual cingulate connectivity

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Previously decreased for guilt in major depressive disorder (MDD) beyond remission

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This RCT shows MDD patients can increase connectivity in one neurofeedback session.

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Active neurofeedback group increase self-esteem vs control neurofeedback group

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Training-induced self-esteem increases correlate with connectivity increases

Emotional Biases and Recurrence in Major Depressive Disorder. Results of 2.5 Years Follow-Up of Drug-Free Cohort Vulnerable for Recurrence

An interesting factor explaining recurrence risk in Major Depressive Disorder (MDD) may be neuropsychological functioning, i.e., processing of emotional stimuli/information. Negatively biased processing of emotional stimuli/information has been found in both acute and (inconclusively) remitted states of MDD, and may be causally related to recurrence of depression. We aimed to investigate self-referent, memory and interpretation biases in recurrently depressed patients in remission and relate these biases to recurrence. We included 69 remitted recurrent MDD-patients (rrMDD-patients), 35-65 years, with ≥2 episodes, voluntarily free of antidepressant maintenance therapy for at least 4 weeks. We tested self-referent biases with an emotional categorization task, bias in emotional memory by free recall of the emotion categorization task 15 min after completing it, and interpretation bias with a facial expression recognition task. We compared these participants with 43 never-depressed controls matched for age, sex and intelligence. We followed the rrMDD-patients for 2.5 years and assessed recurrent depressive episodes by structured interview. The rrMDD-patients showed biases toward emotionally negative stimuli, faster responses to negative self-relevant characteristics in the emotional categorization, better recognition of sad faces, worse recognition of neutral faces with more misclassifications as angry or disgusting faces and less misclassifications as neutral faces (0.001 < p < 0.05). Of these, the number of misclassifications as angry and the overall performance in the emotional memory task were significantly associated with the time to recurrence (p ≤ 0.04), independent of residual symptoms and number of previous episodes. In a support vector machine data-driven model, prediction of recurrence-status could best be achieved (relative to observed recurrence-rate) with demographic and childhood adversity parameters (accuracy 78.1%; 1-sided p = 0.002); neuropsychological tests could not improve this prediction. Our data suggests a persisting (mood-incongruent) emotional bias when patients with recurrent depression are in remission. Moreover, these persisting biases might be mechanistically important for recurrence and prevention thereof.

Assessing Hedonic Bias in Emotional Scene Memory

Abstract. Across studies, memory for emotional events has shown a positivity bias, a negativity bias, and/or an arousal bias, and different types of memory biases have been reported in patients diagnosed with anxiety and mood disorders. Here, we investigated hedonic bias in memory for emotionally evocative scenes in a large sample (n = 625) of healthy young adults, in order to provide normative data on effects of pleasure, arousal, and content on immediate free recall that could facilitate future clinical investigations. Participants first viewed and rated a set of 60 pictures, followed by an unexpected memory test. Across participants, memory data was obtained for 360 different pictures, which served as the unit of analysis. There was neither a systematic positivity nor negativity bias in free recall of emotionally arousing scenes. Rather, memory was enhanced for scenes rated as highly arousing, whether pleasant or unpleasant, with those depicting romantic/sexual love and death/violence remembered equally well, and significantly better than other hedonic contents. Gender differences were not strong. Taken together, these data provide a basic science foundation for assessing hedonic bias in clinical populations.