False Memories for Affective Information in Schizophrenia

Contextual memory engrams, and the neuromodulatory influence of the locus coeruleus

Here, we review the basis of contextual memory at a conceptual and cellular level. We begin with an overview of the philosophical foundations of traversing space, followed by theories covering the material bases of contextual representations in the hippocampus (engrams), exploring functional characteristics of the cells and subfields within. Next, we explore various methodological approaches for investigating contextual memory engrams, emphasizing plasticity mechanisms. This leads us to discuss the role of neuromodulatory inputs in governing these dynamic changes. We then outline a recent hypothesis involving noradrenergic and dopaminergic projections from the locus coeruleus (LC) to different subregions of the hippocampus, in sculpting contextual representations, giving a brief description of the neuroanatomical and physiological properties of the LC. Finally, we examine how activity in the LC influences contextual memory processes through synaptic plasticity mechanisms to alter hippocampal engrams. Overall, we find that phasic activation of the LC plays an important role in promoting new learning and altering mnemonic processes at the behavioral and cellular level through the neuromodulatory influence of NE/DA in the hippocampus. These findings may provide insight into mechanisms of hippocampal remapping and memory updating, memory processes that are potentially dysregulated in certain psychiatric and neurodegenerative disorders.

Investigating False Memory and Illusory Pattern Perception Bias in Schizophrenia Patients with and without Delusions

Background

Whether the false memory dysfunction in schizophrenia is at the early (encoding, perceptual) or later (retrieval) stages and how delusions affect it remains unclear.

Method

In this study, we examined the perception and memory biases in schizophrenia patients with (Sch/D; n = 31) and without delusions (Sch/Nd; n = 32) and compared them with healthy controls (HCs; n = 35). We used the Deese Roediger McDermott (DRM) Paradigm and the Noise Task to measure the false memory and illusory pattern perception (IPP) biases, respectively.

Results

We found that the patient groups performed lower in both the recall and recognition phases for the DRM and the Noise tasks and made more errors compared to the HC group. Additionally, the performance of the Sch/D group was remarkably lower than the Sch/Nd and HC groups.

Conclusions

Our results indicated that the information-processing problem in schizophrenia exists in both the encoding and retrieval stages. Also found significant relationship between the presence of delusions and the increase in cognitive deficits.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10608-023-10393-6.

Psychopathic personality traits are linked to reduced false memories for negative events

Individuals scoring high on psychopathic personality traits process emotional material to a different extent than individuals with few psychopathic traits. Evidence exists that these individuals have impaired emotional memory. The question arises whether this emotional memory impairment has ramifications for the production of emotional false memories. In the present study, we investigated the production of false and true memories for emotional events in a community sample (N = 120) of individuals varying in psychopathic traits (evaluated with the Psychopathic Personality Inventory-Revised [PPI-R] questionnaire). The fearless dominance (FD) component of psychopathy interacted with the emotional impact of to-be-remembered events in the production of false memories, showing fewer negative false memories with increasing levels of FD. At the subjective level, negative false memories were not perceived as vivid memory experiences in high FD individuals. Concerning true memories, higher scores in cold-heartedness were related to fewer true memories for neutral and negative (but not positive) events. These results show that individuals with high psychopathy traits - in particular, FD - do not have a general emotional memory impairment but they process negative material in a different way than individuals with low psychopathic traits and thus are less susceptible to producing false memories for negative events.

Understanding source monitoring subtypes and their relation to psychosis: a systematic review and meta-analysis

AIMS

Source monitoring (SM) is the metacognitive ability to determine the origin of one's experiences. SM is altered in primary psychiatric psychosis, although relationships between SM subtypes, other cognitive domains and symptoms are unclear. Our aims were to synthesize evidence comparing psychosis -with and without hallucinations- and healthy controls classifying SM subtypes by source discrimination (internal/external/reality monitoring) and stimulus modality (visual/auditory/imagined/performed).

METHODS

This systematic review adopted Preferred Reporting Items for Systematic Reviews and Meta-Analyses, Meta-analyses Of Observational Studies in Epidemiology and Population, Intervention, Comparison and Outcomes guidelines. Core demographical and clinical parameters were extracted. Newcastle-Ottawa Scale was used as quality check. SM differences between (i) psychosis patients versus healthy controls and (ii) patients with versus without hallucinations were investigated via random-effect model meta-analysis. The primary effect size measure was standardized mean difference (SMD) in each SM subtype performance (error or accuracy). Heterogeneity, publication biases and meta-regressions were assessed.

RESULTS

Five thousand two hundred and fifty-six records were screened to finally include 44 studies (1566 patients, 1175 controls). Mean Newcastle-Ottawa score was 7.41 out of 9. Few studies measured SM associations with cognition (n = 9) and symptoms (n = 19), with heterogeneous findings. SM performance across all measures was reduced in psychosis versus healthy controls (SMD = 0.458). Internal SM (SMD: errors = 0.513; accuracy = 0.733) and imagined stimuli (SMD: errors = 0.688; accuracy = 0.978) were specifically impaired. Patients with versus without hallucinations showed SM deficits only for externalizing (SMD = 0.410) and imagined/auditory (SMD = 0.498/0.277) errors.

CONCLUSION

The proposed classifications highlight specific SM deficits for internal/imagined stimuli in psychosis, providing evidence-based indications to design and interpret future studies.

Do patients with hallucinations imagine speech right?

A direct relationship between auditory verbal hallucinations (AVHs) and decreased left-hemispheric lateralization in speech perception has been often described, although it has not been conclusively proven. The specific lateralization of AVHs has been poorly explored. However, patients with verbal hallucinations show a weak Right Ear Advantage (REA) in verbal perception compared to non AVHs listeners suggesting that left-hemispheric language area are involved in AVHs. In the present study, 29 schizophrenia patients with AVHs, 31 patients with psychotic bipolar disorder who experienced frequent AVHs, 27 patients with schizophrenia who had never experienced AVHs and 57 healthy controls were required to imagine hearing a voice in one ear alone. In line with previous evidence healthy controls confirmed the expected REA for auditory imagery, and the same REA was also found in non-hallucinator patients. However, in line with our hypothesis, patients with schizophrenia and psychotic bipolar disorder with AVHs showed no lateral bias. Results extend the relationship between abnormal asymmetry for verbal stimuli and AVHs to verbal imagery, suggesting that atypical verbal imagery may reflect a disruption of inter-hemispheric connectivity between areas implicated in the generation and monitoring of verbal imagery and may be predictive of a predisposition for AVHs. Results also indicate that the relationship between AVHs and hemispheric lateralization for auditory verbal imagery is not specific to schizophrenia but may extend to other disorders as well.

News and Commercials: Binding Deficits for Complex Information in Schizophrenia

Memory for complex content is severely impaired in patients with schizophrenia spectrum disorders, which might make processing of daily information such as news and commercials particularly challenging. The goal of the present study was to assess the impairment of everyday memory in patients with schizophrenia. Healthy controls (HC) and patients with schizophrenia (SZ) were asked to watch a selection of six news segments and six commercials and complete a recognition task on the content of these video clips. All participants completed a neuropsychological test battery comprising measures of attention, working and episodic memory, and executive function. The total number of correctly recognized items was significantly lower in the SZ group. In contrast, the number of false recognitions was alike in both news and commercials paradigm. We conclude that memory in patients with schizophrenia is more prone to omissions than distortions for complex everyday stimuli. The results offer further support for impaired binding in SZ patients. Memory in SZ suffices to reject false multi-feature items on grounds of identifying at least one feature as incorrect but does not suffice to recall all features of a complex item and affirm it as correct.

Emotional Prosody Effects on Verbal Memory in Euthymic Patients With Bipolar Disorder

A growing body of evidence suggests that emotional prosody influences the ability to remember verbal information. Although bipolar disorder (BD) has been shown to be associated with deficits in verbal memory and emotional processing, the relation between these processes in this population remains unclear. In the present study, we aimed to investigate the impact of emotional prosody on verbal memory in euthymic BD patients compared with controls. Participants were randomly divided into three subgroups according to different prosody listening conditions (a story read with a positive, negative, or neutral prosody) and effects on a yes-no recognition memory task were investigated. Results showed that euthymic bipolar patients remembered comparable numbers of words after listening to the story with a negative or neutral prosody but remembered fewer words after listening to the positive version compared with healthy controls. Results suggest that verbal memory is hindered in BD patients after listening to the story read with a positive prosody. This recognition bias for information with a positive prosody may lead to negative intrusive verbal memories and poor emotion regulation.

Experimental Effects of Acute Exercise on Prospective Memory and False Memory

Research demonstrates that acute exercise can enhance retrospective episodic memory performance. However, limited research has examined the effects of acute exercise on prospective memory, and no studies have examined the effects of exercise on false memory performance. This study examined the potential effects of acute exercise on prospective memory and false memory performance. A between-group randomized controlled trial was employed, with participants (college students; M_age = 20 years) randomized into an exercise group (15-minute acute bout of treadmill walking; N = 25) or a control group (15 minutes of sitting; N = 26). Prospective memory was assessed from two laboratory and two naturalistic assessments outside the lab. False memory was assessed using a word-list trial. There were no statistically significant differences in prospective memory based on group allocation (F_Group×Time = 1.17; P = 0.32; η²= 0.06). However, the control group recalled more false words and had a higher rate of false memory recognition (F_Group×Time = 3.15; P = 0.01; η²= 0.26). These findings indicate that acute moderate-intensity aerobic exercise is not associated with prospective memory performance but provides some suggestive evidence that acute exercise may reduce the rate of false memories.