Schizophrenia and prospective memory impairments: a review

Active forgetting and neuropsychiatric diseases

Recent and pioneering animal research has revealed the brain utilizes a variety of molecular, cellular, and network-level mechanisms used to forget memories in a process referred to as "active forgetting". Active forgetting increases behavioral flexibility and removes irrelevant information. Individuals with impaired active forgetting mechanisms can experience intrusive memories, distressing thoughts, and unwanted impulses that occur in neuropsychiatric diseases. The current evidence indicates that active forgetting mechanisms degrade, or mask, molecular and cellular memory traces created in synaptic connections of "engram cells" that are specific for a given memory. Combined molecular genetic/behavioral studies using Drosophila have uncovered a complex system of cellular active-forgetting pathways within engram cells that is regulated by dopamine neurons and involves dopamine-nitric oxide co-transmission and reception, endoplasmic reticulum Ca2+ signaling, and cytoskeletal remodeling machinery regulated by small GTPases. Some of these molecular cellular mechanisms have already been found to be conserved in mammals. Interestingly, some pathways independently regulate forgetting of distinct memory types and temporal phases, suggesting a multi-layering organization of forgetting systems. In mammals, active forgetting also involves modulation of memory trace synaptic strength by altering AMPA receptor trafficking. Furthermore, active-forgetting employs network level mechanisms wherein non-engram neurons, newly born-engram neurons, and glial cells regulate engram synapses in a state and experience dependent manner. Remarkably, there is evidence for potential coordination between the network and cellular level forgetting mechanisms. Finally, subjects with several neuropsychiatric diseases have been tested and shown to be impaired in active forgetting. Insights obtained from research on active forgetting in animal models will continue to enrich our understanding of the brain dysfunctions that occur in neuropsychiatric diseases.

Associations between intraindividual reaction time variability and prospective memory performance in patients with schizophrenia and healthy controls

Introduction: Patients with schizophrenia exhibit prospective memory (PM) impairment. Intraindividual reaction time variability (IIRTV) is an index of attentional control that is required for PM. This study examined the differences in IIRTV between patients with schizophrenia and healthy controls and the relationship between IIRTV and PM performance.Method: Thirty-nine patients with schizophrenia and forty-two healthy controls were recruited to complete a PM task and the Sustained Attention to Response Task. IIRTV was calculated as the coefficient of variation (mean/SD) of reaction time over correctly responded trials in these tasks.Results: Patients with schizophrenia showed lower PM accuracy and increased IIRTV, while the associations between PM accuracy and IIRTV were significant in healthy controls but not in patients with schizophrenia.Conclusion: These findings suggest impaired PM and relationship between PM and attentional control in patients with schizophrenia.

Risk Factors for Psychotic Relapse After Dose Reduction or Discontinuation of Antipsychotics in Patients With Chronic Schizophrenia. A Meta-Analysis of Randomized Controlled Trials

BACKGROUND AND HYPOTHESIS

Although maintenance treatment with antipsychotics protects against psychotic relapse, high doses may hamper recovery. Therefore, dose reduction or discontinuation may be considered in patients with chronic schizophrenia. Here, we identified risk factors for psychotic relapse when doses are reduced.

STUDY DESIGN

We systematically searched MEDLINE, EMBASE, and PsycINFO from January 1950 through January 2021 and reviewed randomized controlled trials (RCTs) that reported relapse rates after antipsychotic dose reduction or discontinuation in patients with chronic schizophrenia. We calculated relative risks (RRs) with 95% confidence intervals (CIs) per person-year and sought to identify potential risk factors for relapse. The study is registered with PROSPERO (CRD42017058296).

STUDY RESULTS

Forty-seven RCTs (54 patient cohorts, 1746 person-years) were included. The RR for psychotic relapse with dose reduction/discontinuation versus maintenance treatment was 2.3 per person-year (95% CI: 1.9 to 2.8). The RR was higher with antipsychotic discontinuation, dose reduction to less than 3-5 mg haloperidol equivalent (HE), or relatively rapid dose reduction (<10 weeks). The RR was lower with long-acting injectable agents versus oral antipsychotic dose reduction. Other factors that increased the risk of psychotic relapse were younger age and short follow-up time.

CONCLUSIONS

Clinicians should take several risk factors for psychotic relapse into account when considering dose reduction in patients with chronic schizophrenia. Studies of a relatively fast reduction in antipsychotic dose support a minimum dose of 3-5 mg HE. However, if the dose is tapered more gradually, relapses related to medication withdrawal might be avoided, possibly enabling lower-end doses to be achieved.

An ecologically sensitive measure of executive cognition (the Breakfast Task) improves prediction of functional outcome in schizophrenia

Previous work has found that the Breakfast Task (BT), a computerized, ecologically informed executive ability measure, is sensitive to group differences in aging, acquired brain injury, and Parkinson's disease. We investigated whether this measure improves the prediction of functional status over and above standard measures of general intellectual ability, relationship perception, life skills, and symptom severity in individuals with schizophrenia. Regression analyses were conducted to evaluate the joint and incremental validity of the BT in predicting functional disability scores on the World Health Organization Disability Assessment Scale (WHODAS 2.0). Analyses with combined patient (n = 25) and control (n = 32) participants showed that participant status (patients versus control) was the only significant predictor of functional outcome. However, in the patient data, the proportion of variance accounted for improved significantly (model R² of 4% vs. 25%) when BT scores were added to a model containing clinical (Brief Psychiatric Rating Scale), social (Relationships Across Domains), intellectual (Wechsler Abbreviated Scale of Intelligence), and life skills (Canadian Objective Assessment of Life Skills) measures. Results suggest that the BT, a tool that captures complex executive functioning, improves the prediction of disability in patients with schizophrenia and has potential assessment applications.

Multi-target derivatives of D2AAK1 as potential antipsychotics - the effect of the substitution in the indole moiety

Schizophrenia is a complex disease which is best treated with multi-target drugs, such as atypical antipsychotics. Previously, using structure-based virtual screening we found a virtual hit D2AAK1 with nanomolar affinity to dopamine and serotonin receptors important in schizophrenia pharmacotherapy. As a part of optimization campaign of D2AAK1 we obtained its 17 derivatives also displaying a multi-target profile. Selected compounds were tested against off-targets in schizophrenia, i.e. histamine H 1 receptor and muscarinic M 1 receptor and did not display considerable affinity to these receptors. Two most promising compounds were subjected to behavioral studies. These compounds decreased amphetamine-induced hyperactivity in mice which indicates their antipsychotic potential. The compounds did not interfere with the memory consolidation in mice as determined in the passive avoidance test. The favorable pharmacological profile of the compounds was rationalized using molecular modeling.

Autobiographical memory in schizophrenia: The role of metacognition

BACKGROUND

Autobiographical memory is an important component of declarative memory, which refers to the ability to recall personal events that happened in the past. This requires that the person senses or experiences himself/herself in the past (i.e., conscious recollection). For people with schizophrenia, conscious recollection can be particularly difficult, resulting in difficulty accessing detailed, specific autobiographical information. Our hypothesis is that the ability to monitor and think about one's cognitive processes (metacognition) is a requisite for conscious recollection, and that it mediates the association between having schizophrenia and recalling fewer specific, personal memories.

METHODS

Participants were 30 adults with schizophrenia and 30 matched healthy controls. The main assessment instruments were the Metacognition Assessment Scale-Abbreviated (MAS-A) and the Autobiographical Memory Test (AMT). Severity of symptoms was assessed using the Positive and Negative Syndrome Scale (PANSS) for schizophrenia. Cognitive performance was measured with the Screen for Cognitive Impairment in Psychiatry (SCIP). Mediation analysis was conducted following Baron and Kenny's procedure.

RESULTS

People with schizophrenia had more semantic associations and fewer specific memories than controls in the AMT. Metacognition (MAS-A total score) partially mediated the association between having schizophrenia and recalling fewer specific past events, even after controlling for cognitive impairment as a potential confounding source.

CONCLUSIONS

Metacognitive ability, which can be improved with available programs, intervenes in the process of accessing autobiographical memories in people with schizophrenia. Practical implications of this finding are discussed.

Brief report: A randomized controlled trial of a compensatory cognitive training to improve prospective memory performance in people with schizophrenia or depression

People with schizophrenia or depression have prospective memory (PM) deficits, which affect their daily living. Given the paucity of research into training to correct PM deficits, we subjected a group of participants to a Chinese version of the PM module of the Cognitive Compensatory Training (CCT-C-PM) intervention to study its effect on their PM performance. Specifically, we independently randomized two diagnostic cohorts (schizophrenia and depression) into control groups (occupational therapy only) or experimental groups (CCT-C-PM and occupational therapy). The schizophrenia cohort had 17 participants in its control group and 23 participants in its experimental group. The depression cohort had 10 participants in its control group and 12 participants in its experimental group. The sociodemographic information of the participants was collected. Their symptoms and PM performances were measured at baseline and after treatment (after the completion of the CCT-C-PM intervention in the experimental group and the same timeframe in the control group). The treatment effects were examined by a repeated measure analysis of variance/analysis of covariance and a post hoc Scheffé test. The effect sizes (Cohen's d) of treatments against the controls were also calculated. There was no difference between the experimental and control groups in either cohort in terms of sociodemographic data, symptoms, and PM measures at baseline. The sex combination differed across the groups in the depression cohort. We found that the CCT-C-PM improved PM, especially event-based PM, for which large effect sizes were seen. The effect on time-based PM was unclear and requires future study. Our findings suggest that the CCT-C-PM is a viable training method for improving PM.

Cognitive insight is correlated with cognitive impairments and contributes to medication adherence in schizophrenia patients

OBJECTIVE

Cognitive insight refers to the ability to distance oneself from and evaluate one's own beliefs and interpretations. Little is known about whether cognitive insight could influence medication adherence in schizophrenia patients. This study examined the role of cognitive insight in medication adherence and how it would interact with neuropsychological functions.

METHODS

Ninety clinically-stable schizophrenia patients completed the Beck's Cognitive Insight Scale (BCIS) and tasks measuring prospective (PM) and other neurocognitive functions. Medication adherence was estimated using a multi-axial method comprising interview, clinician-rating, pharmacy refill record and pill counting. Correlational and regression analyses were conducted to examine whether cognitive insight and PM would be associated with mediation adherence. Post-hoc mediational analysis was performed to examine the interplay between cognitive insight, PM and medication adherence.

RESULTS

Clinical insight and cognitive insight together significantly influenced participants' medication adherence, after neurocognitive functions and psychopathology were accounted for. Time-based PM, compared with other neurocognitive functions, affected medication adherence more strongly.

CONCLUSIONS

Cognitive insight complements clinical insight in affecting medication adherence in schizophrenia patients.

From retrospective to prospective memory research: a framework for investigating the deactivation of intentions

The definition of episodic memory has evolved into a multifaceted concept that gathered great attention in several research areas in psychology and neuroscience. Prospective memory (PM), or the ability to remember to perform delayed intentions at a later moment in the future, represents one side of this capacity for which that has been a growing interest. In this review, we examined a counterintuitive finding: PM intentions may persist and affect our behaviour despite successful goal attainment and task completion, which in daily life may be as serious as taking medication twice. This review aims to elucidate the existing knowledge and identify some unresolved questions concerning this specific memory failure. Therefore, this review provides an overview of the uprising research dedicated to both PM omission and commission errors, including an analysis of its definitions, of the current theoretical approaches of PM retrieval, and the main procedures used in this field to offer an integrative perspective on this topic. Finally, the last section is devoted to discussing future directions to test the predictions of our suggested theoretical explanations for PM deactivation. This might be an avenue for research that is likely to extend our understanding of episodic memory's usefulness in everyday life.

The Relationship between Life Course Socioeconomic Conditions and Objective and Subjective Memory in Older Age

While objective memory performance in older adults was primarily shown to be affected by education as indicator of life course socioeconomic conditions, other life course socioeconomic conditions seem to relate to subjective memory complaints. However, studies differ in which life course stages were investigated. Moreover, studies have explored these effects in an isolated way, but have not yet investigated their unique effect when considering several stages of the life course simultaneously. This study, therefore, examined the respective influence of socioeconomic conditions from childhood up to late-life on prospective memory (PM) performance as an objective indicator of everyday memory as well as on subjective memory complaints (SMC) in older age using structural equation modeling. Data came from two waves of the Vivre-Leben-Vivere aging study (n=993, Mage=80.56). The results indicate that only socioeconomic conditions in adulthood significantly predicted late-life PM performance. PM performance was also predicted by age and self-rated health. In contrast, SMC in older age were not predicted by socioeconomic conditions at any stage of the life course but were predicted by level of depression. In line with the cognitive reserve hypothesis, present results highlight the significance of education and occupation (adulthood socioeconomic conditions) for cognitive functioning in later life.

Correlations between age, biomedical variables, and cognition in patients with schizophrenia

Objective

To illustrate the influence of clinical variables on cognition performance in patients with schizophrenia (SCZ).

Methods

Using the 66nao Brain Training device (a novel measurement tool), the cognitive performance of 99 patients with SCZ was evaluated. Patients were diagnosed by the ICD-10 diagnostic criteria for SCZ, and their age were 16–68 years old. Furthermore, we explored the relationship between age, biomedical variables and specific cognitive domains in patients with SCZ. Patients were divided into two groups: various of cognitive domains impairment group and non-impairment group according to the norm scores. All data were analyzed using RStudio Version 1.0.44 (RStudio, Inc.)

Results

Patients with SCZ had obvious cognitive impairment in total and five subdomains of cognitive function. We found that 1) SCZ patients with impaired cognitive total score experienced significant older age and longer illness duration compared with those with normal cognitive total score. 2) SCZ patients with impaired memory experienced significant older age compared with those with normal memory. 3) SCZ patients with impaired attention showed significant lower serum triglyceride (TG) level compared with those with normal attention. 4) SCZ patients with impaired flexibility performed significant longer illness duration compared with those with normal flexibility. 5) SCZ patients with impaired cognitive agility performed significant older age, longer duration, and higher systolic blood pressure (SBP) compared with those with normal cognitive agility. 6) The age, illness duration and SBP in patients with impaired time perception were marginally different from those of subjects with normal time perception.

Conclusion

There are five dimensions (memory, attention, flexibility, cognitive agility, and time perception) of cognitive dysfunction in SCZ patients. Age, illness duration, TG, and SBP might play vital roles in various subdomains of the cognitive deficits respectively in patients with SCZ.

Fine structure analysis of perineuronal nets in the ketamine model of schizophrenia

Perineuronal nets (PNNs) represent a highly condensed specialized form of brain extracellular matrix (ECM) enwrapping mostly parvalbumin-positive interneurons in the brain in a mesh-like fashion. PNNs not only regulate the onset and completion of the critical period during postnatal brain development, control cell excitability, and synaptic transmission but are also implicated in several brain disorders including schizophrenia. Holes in the perineuronal nets, harboring the synaptic contacts, along with hole-surrounding ECM barrier can be viewed as PNN compartmentalization units that might determine the properties of synapses and heterosynaptic communication. In this study, we developed a novel open-source script for Fiji (ImageJ) to semi-automatically quantify structural alterations of PNNs such as the number of PNN units, area, mean intensity of PNN marker expression in 2D and 3D, shape parameters of PNN units in the ketamine-treated Sprague-Dawley rat model of schizophrenia using high-resolution confocal microscopic images. We discovered that the mean intensity of ECM within PNN units is inversely correlated with the area and the perimeter of the PNN holes. The intensity, size, and shape of PNN units proved to be three major principal factors to describe their variability. Ketamine-treated rats had more numerous but smaller and less circular PNN units than control rats. These parameters allowed to correctly classify individual PNNs as derived from control or ketamine-treated groups with ≈85% reliability. Thus, the proposed multidimensional analysis of PNN units provided a robust and comprehensive morphometric fingerprinting of fine ECM structure abnormalities in the experimental model of schizophrenia.

Risk Factors for Psychotic Relapse After Dose Reduction or Discontinuation of Antipsychotics in Patients With Chronic Schizophrenia: A Systematic Review and Meta-analysis

High doses of antipsychotics in patients with chronic schizophrenia might lead to more severe side effects and possibly hamper recovery, but dose reduction carries the risk of psychotic relapse. It would be helpful to establish risk factors for relapse during dose reduction. We systematically searched MEDLINE, EMBASE, and PsycINFO from January 1950 through June 2019 and reviewed studies that reported on relapse rates (event rates [ERs]) after dose reduction or discontinuation of antipsychotics in cohorts of patients with chronic schizophrenia. We calculated ERs (with 95% CIs) per person-year and sought to identify potential risk factors, such as patient characteristics, dose reduction/discontinuation characteristics, and study characteristics. Of 165 publications, 40 describing dose reduction or discontinuation in 46 cohorts (1677 patients) were included. The pooled ER for psychotic relapse was 0.55 (95% CI 0.46–0.65) per person-year. The ER was significantly higher in inpatients, patients with a shorter duration of illness, patients in whom antipsychotics were discontinued or in whom the dose was reduced to less than 5 mg haloperidol equivalent, studies with a short follow-up or published before 1990, and studies in which relapse was based on clinical judgment (ie, rating scales were not used). Clinicians should consider several robust risk factors for psychotic relapse in case of dose reduction in chronic schizophrenia.

The effect of implementation intentions on prospective memory performance in patients with schizophrenia: A multinomial modeling approach

Patients with schizophrenia (SCZ) consistently show prospective memory (PM) impairments, and the technique of implementation intentions has been shown to improve PM performance in these patients. PM is considered to have prospective and retrospective components. However, it remains unclear which component of PM is impaired in patients with SCZ and which component(s) is facilitated by implementation intentions (II). The present study aimed to examine these two issues. Forty-two patients with SCZ and 42 matched healthy controls were randomly assigned to an II group or a typical instruction group. All participants were administered a color-matching PM task. Results showed that, using a multinomial-modeling approach, patients with SCZ exhibited impairment in the retrospective component of PM. In addition, while II improved the prospective PM component in healthy controls, both prospective and retrospective PM components in patients with SCZ were improved. Together, our results shed light on the mechanism of PM impairment in SCZ patients and the mechanism of II in improving PM performance.

Effects of Exercise on Memory Interference in Neuropsychiatric Disorders

There are several mechanisms that cause memory impairment, including motivated forgetting, active forgetting, natural decay, and memory interference. Interference occurs when one is attempting to recall something specific, but there is conflicting information making it more difficult to recall the target stimuli. In laboratory settings, it is common to measure memory interference with paired associate tasks-usually utilizing the AB-CD, AB-AC, AB-ABr, or AB-DE AC-FG method. Memory impairments are frequent among those with neuropsychiatric disorders such as depression, schizophrenia, and multiple sclerosis. The memory effects of each condition differ, but are all related to alterations in brain physiology and general memory deterioration. Exercise, or physical activity, has been demonstrated to attenuate memory interference in some cases, but the mechanisms are still being determined. Further research is needed on memory interference, in regard to exercise and neuropsychiatric disorders.

Cognition and Related Neural Findings on Methamphetamine Use Disorder: Insights and Treatment Implications From Schizophrenia Research

Despite the prevalence of methamphetamine (meth) use disorder, research on meth is disproportionately scarce compared to research on other illicit drugs. Existing evidence highlights cognitive deficits as an impediment against daily function and treatment of chronic meth use. Similar deficits are also observed in schizophrenia, and this review therefore draws on schizophrenia research by examining similarities and differences between the two disorders on cognition and related neural findings. While meth use disorder and schizophrenia are two distinct disorders, they are highly co-morbid and share impairments in similar cognitive domains and altered brain structure/function. This narrative review specifically identifies overlapping features such as deficits in learning and memory, social cognition, working memory and inhibitory/impulse control. We report that while working memory deficits are a core feature of schizophrenia, such deficits are inconsistently observed following chronic meth use. Similar structural and functional abnormalities are also observed in cortical and limbic regions between the two disorders, except for cingulate activity where differences are observed. There is growing evidence that targeting cognitive symptoms may improve functional outcome in schizophrenia, with evidence of normalized abnormal brain activity in regions associated with cognition. Considering the overlap between meth use disorder and schizophrenia, targeting cognitive symptoms in people with meth use disorder may also improve treatment outcome and daily function.

Prospective memory in clinical populations

OBJECTIVE

Prospective memory (PM) has emerged as a form of episodic memory that is frequently impaired in a variety of clinical populations. Neuropsychologists who routinely evaluate these populations are often unaware of the possibility of PM deficits or the impact these deficits may have on everyday functioning. The objective of this special issue is to provide an overview of the nature of prospective deficits in a range of clinical populations, to discuss neuropsychological assessment techniques, and to critically evaluate management strategies.

METHOD

We solicited papers from established researchers and issued a general call for papers for the special issue on PM in clinical populations.

RESULTS

We received submissions from the nine authors that we solicited. These submissions range from developmental disorders, including autism, attention deficit hyperactivity disorder, and dyslexia; to disorders of adulthood, such as schizophrenia, HIV, brain injury, and multiple sclerosis; and finally disorders that tend to occur at older ages, such as Parkinson's disease and mild cognitive impairment. In addition, we have included four original research articles that provide novel data on other populations. These are children and adolescents with 22q11.2 deletion syndrome, first-degree relatives of people with schizophrenia, individuals with mild brain injury, and individuals with idiopathic REM sleep behavioral disorder.

CONCLUSIONS

The issue highlights the need for clinical neuropsychologists to be aware of the possible existence of deficits in PM in a variety of clinical populations and the importance of both assessment and management strategies to reduce the impact on daily life.

A comparison of different types of prospective memory reminders in schizophrenia

People with schizophrenia often experience difficulties with prospective memory (PM), but few empirical studies have directly compared the effectiveness of different types of reminders in remediating these difficulties. In the present study, two distinct types of reminders were compared to a standard (no reminder) condition in outpatients with schizophrenia (n = 30) and controls (n = 30). Using an adapted version of the well-validated laboratory PM measure, Virtual Week, participants were asked to complete three different conditions (counterbalanced), in which they were (i) provided with access to self-initiated reminders, (ii) provided with experimenter-initiated reminders, and (iii) completed a standard (no-reminder) condition. Both groups benefited from the provision of reminders, but self-initiated reminders were the most beneficial, particularly for time-based tasks. These data align with a broader literature that shows PM can be enhanced by the use of reminders. However, it extends this literature in an important way by showing that these benefits are equivalent for people with schizophrenia, and may be greatest where access to reminders is self-initiated. The implications of these data for the development of rehabilitative interventions are discussed.