Changes in neurocognitive functioning during transition to manifest disease: comparison of individuals at risk for schizophrenic and bipolar affective psychoses

Longitudinal change in neurocognitive functioning in children and adolescents at clinical high risk for psychosis: a systematic review

Clinical high risk of psychosis (CHR-P) population has become an attractive area of interest in preventing transitions to psychosis. The consequences of developing a psychotic disorder may be worse in cases of early onset. Thus, childhood and adolescence represent a critical developmental window, where opportunities to gain social and adaptive abilities depend on the individuals' neurocognitive performance. There have been previous syntheses of the evidence regarding neurocognitive functioning in CHR-P individuals and its longitudinal changes. However, there has been less focus on children and adolescents at CHR-P. A multistep literature search was performed from database inception until July 15th, 2022. PRIMSA/MOOSE compliant systematic review and PROSPERO protocol were used to identify studies reporting on longitudinal changes in neurocognitive functioning in children and adolescents (mean age of sample ≤ 18 years) at CHR-P and matched healthy control (HC) group. A systematic review of identified studies was then undertaken. Three articles were included, resulting in a total sample size of 151 CHR-P patients [mean (SD) age, 16.48 (2.41) years; 32.45% female] and 64 HC individuals [mean (SD) age, 16.79 (2.38) years; 42.18% female]. CHR-P individuals had worse outcomes in verbal learning, sustained attention and executive functioning domains compared to HC. Individuals taking antidepressants had better outcomes in verbal learning in contrast with those taking antipsychotics. In children and adolescents, neurocognition may be already impaired before the psychosis onset, and remains stable during the transition to psychosis. Further study should be performed to obtain more robust evidence.

Neuropsychological Performance Among Individuals at Clinical High-Risk for Psychosis vs Putatively Low-Risk Peers With Other Psychopathology: A Systematic Review and Meta-Analysis

BACKGROUND AND HYPOTHESIS

Youth at clinical high-risk (CHR) for psychosis present with neuropsychological impairments relative to healthy controls (HC), but whether these impairments are distinguishable from those seen among putatively lower risk peers with other psychopathology remains unknown. We hypothesized that any excess impairment among CHR cohorts beyond that seen in other clinical groups is minimal and accounted for by the proportion who transition to psychosis (CHR-T).

STUDY DESIGN

We performed a systematic review and meta-analysis of studies comparing cognitive performance among CHR youth to clinical comparators (CC) who either sought mental health services but did not meet CHR criteria or presented with verified nonpsychotic psychopathology.

STUDY RESULTS

Twenty-one studies were included representing nearly 4000 participants. Individuals at CHR showed substantial cognitive impairments relative to HC (eg, global cognition: g = -0.48 [-0.60, -0.34]), but minimal impairments relative to CC (eg, global cognition: g = -0.13 [-0.20, -0.06]). Any excess impairment among CHR was almost entirely attributable to CHR-T; impairment among youth at CHR without transition (CHR-NT) was typically indistinguishable from CC (eg, global cognition, CHR-T: g = -0.42 [-0.64, -0.19], CHR-NT: g = -0.09 [-0.18, 0.00]; processing speed, CHR-T: g = -0.59 [-0.82, -0.37], CHR-NT: g = -0.12 [-0.25, 0.07]; working memory, CHR-T: g = -0.42 [-0.62, -0.22], CHR-NT: g = -0.03 [-0.14, 0.08]).

CONCLUSIONS

Neurocognitive impairment in CHR cohorts should be interpreted cautiously when psychosis or even CHR status is the specific clinical syndrome of interest as these impairments most likely represent a transdiagnostic vs psychosis-specific vulnerability.

Meta-analysis of longitudinal neurocognitive performance in people at clinical high-risk for psychosis

Persons at clinical high-risk for psychosis (CHR) are characterised by specific neurocognitive deficits. However, the course of neurocognitive performance during the prodromal period and over the onset of psychosis remains unclear. The aim of this meta-analysis was to synthesise results from follow-up studies of CHR individuals to examine longitudinal changes in neurocognitive performance. Three electronic databases were systematically searched to identify articles published up to 31 December 2021. Thirteen studies met inclusion criteria. Study effect sizes (Hedges' g) were calculated and pooled for each neurocognitive task using random-effects meta-analyses. We examined whether changes in performance between baseline and follow-up assessments differed between: (1) CHR and healthy control (HC) individuals, and (2) CHR who did (CHR-T) and did not transition to psychosis (CHR-NT). Meta-analyses found that HC individuals had greater improvements in performance over time compared to CHR for letter fluency (g = -0.32, p = 0.029) and digit span (g = -0.30, p = 0.011) tasks. Second, there were differences in longitudinal performance of CHR-T and CHR-NT in trail making test A (TMT-A) (g = 0.24, p = 0.014) and symbol coding (g = -0.51, p = 0.011). Whilst CHR-NT improved in performance on both tasks, CHR-T improved to a lesser extent in TMT-A and had worsened performance in symbol coding over time. Together, neurocognitive performance generally improved in all groups at follow-up. Yet, evidence suggested that improvements were less pronounced for an overall CHR group, and specifically for CHR-T, in processing speed tasks which may be a relevant domain for interventions aimed to enhance neurocognition in CHR populations.

A systematic review of premorbid cognitive functioning and its timing of onset in schizophrenia spectrum disorders

Cognitive impairments are core features of established schizophrenia spectrum disorders (SSD). However, it remains unclear whether specific cognitive functions are differentially impaired pre-onset and at what age these impairments can be detected. The purpose of this review was to elucidate these issues through a systematic summary of results from longitudinal studies investigating impairment in specific cognitive domains as antecedents of SSD. Relevant studies were identified by electronic and manual literature searches and included any original study of cognitive domains any time pre-onset of SSDs that included a control group. Effect sizes were calculated by domain for studies comparing high-risk participants who developed SSD with those who did not. The strongest evidence for impairment pre-onset was for mental processing speed, verbal learning and memory, executive function, and social cognition. Some verbal impairments, like language abilities at age 3 and verbal learning and memory at age 7, may develop as static deficits. Conversely, some non-verbal impairments, like mental processing speed, visuospatial abilities, and visual working memory manifest as developmental lag and become significant later in life. Most effect sizes were small to moderate, except for verbal fluency (d' = 0,85), implying this impairment as central in high-risk participants who develop SSD. The present review documents extensive cognitive impairments pre-onset of SSD, and that these impairments start early in life, in line with the neurodevelopmental hypothesis of schizophrenia. Increased knowledge about cognitive impairments preonset can provide a better basis for understanding the complex pathogenesis of SSD as well as informing cognitive remediation programs.

Study protocol for a pilot high-intensity interval training intervention in inpatient mental health settings: a two-part study using a randomised controlled trial and naturalistic study design

BACKGROUND

Severe mental illnesses (SMI), including schizophrenia spectrum disorder, bipolar disorder and major depressive disorder, are associated with physical health comorbidities and premature mortality. Physical activity and structured exercise have a beneficial impact on cardiometabolic risk and ameliorate mental health symptomology and cognition. This protocol describes a feasibility study for a high-intensity interval training (HIIT) intervention among inpatients with SMI, to improve their physical and mental health.

METHODS

The feasibility study follows a two-part design owing to COVID-19-related adaptations to project design: (a) a non-blinded randomised controlled trial (RCT) of 12 weeks of bicycle-based HIIT, delivered twice weekly in a face-to-face, one-to-one setting, compared to treatment as usual (TAU) and (b) a naturalistic study of inpatient HIIT; eligible participants will be invited to two sessions of HIIT per week, delivered by the research team remotely or in person. Additionally, participants in the naturalistic study may use the bike to conduct self-directed sessions of their chosen length and intensity. We will measure the feasibility and acceptability of the HIIT intervention as primary outcomes, alongside secondary and tertiary outcomes evaluating the physical, mental and cognitive effects of HIIT. The study aims to recruit 40 patients to the RCT and 6-8 patients to the naturalistic design.

DISCUSSION

Exercise is a modifiable lifestyle barrier that can reverse cardiometabolic disease risk. If HIIT is found to be feasible and acceptable in inpatients with SMI, there would be scope for large-scale work to evaluate the clinical, cost and implementation effectiveness of HIIT in inpatient mental health settings.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03959735 . Registered June 22, 2019.

Perspectives on implementing HIIT interventions for service users in inpatient mental health settings: A qualitative study investigating patient, carer and staff attitudes

BACKGROUND

High intensity interval training (HIIT) may have beneficial effects among people living with severe mental illness (SMI), however there remains an absence of information on attitudes of key stakeholders (e.g. family carers, healthcare professionals) towards offering HIIT interventions in psychiatric inpatient settings. This study sought to qualitatively investigate, in inpatients with SMI, carer and staff groups, perspectives on implementing HIIT interventions for patient groups in inpatient settings.

METHODS

Seven focus groups and one individual interview were conducted. These included three focus groups held with inpatients with SMI (n=13), two held with carers (n=15), and two held with healthcare professionals working in inpatient settings (n=11). An additional individual interview was conducted with one patient participant.

RESULTS

Two key themes emerged from the data, across all participants, that reflected the 'Positivity' in the application of HIIT interventions in psychiatric inpatient settings with beliefs that it would help patients feel more relaxed, build their fitness, and provide a break from the monotony of ward environments. The second theme related to 'Implementation concerns', that reflected subthemes about i) patient motivation, ii) patient safety and iii) practical logistical factors, including having access to the right sports clothing and staff availability.

LIMITATIONS

Investigations were limited to one mental health service provider and participants might already be those with an interest in exercise-based interventions.

CONCLUSIONS

HIIT interventions for SMI inpatients were perceived positively by key stakeholders. However, individual and organisational barriers to successful implementation are identified and should be addressed in advance.

Predicting the individual risk of psychosis conversion in at-risk mental state (ARMS): a multivariate model reveals the influence of nonpsychotic prodromal symptoms

To improve the prediction of the individual risk of conversion to psychosis in UHR subjects, by considering all CAARMS' symptoms at first presentation and using a multivariate machine learning method known as logistic regression with Elastic-net shrinkage. 46 young individuals who sought help from the specialized outpatient unit at Sainte-Anne hospital and who met CAARMS criteria for UHR were assessed, among whom 27 were reassessed at follow-up (22.4 ± 6.54 months) and included in the analysis. Elastic net logistic regression was trained, using CAARMS items at baseline to predict individual evolution between converters (UHR-P) and non-converters (UHR-NP). Elastic-net was used to select the few CAARMS items that best predict the clinical evolution. All validations and significances of predictive models were computed with non-parametric re-sampling strategies that provide robust estimators even when the distributional assumption cannot be guaranteed. Among the 25 CAARMS items, the Elastic net selected 'obsessive-compulsive symptoms' and 'aggression/dangerous behavior' as risk factors for conversion while 'anhedonia' and 'mood swings/lability' were associated with non-conversion at follow-up. In the ten-fold stratified cross-validation, the classification achieved 81.8% of sensitivity (P = 0.035) and 93.7% of specificity (P = 0.0016). Non-psychotic prodromal symptoms bring valuable information to improve the prediction of conversion to psychosis. Elastic net logistic regression applied to clinical data is a promising way to switch from group prediction to an individualized prediction.

Clinical Validity of DSM-5 Attenuated Psychosis Syndrome: Advances in Diagnosis, Prognosis, and Treatment

IMPORTANCE

Since the release of the DSM-5 diagnosis of attenuated psychosis syndrome (DSM-5-APS) in 2013, several research studies have investigated its clinical validity. Although critical and narrative reviews have reviewed these progresses, no systematic review has comprehensively summarized the available evidence regarding the clinical validity of DSM-5-APS.

OBJECTIVE

To provide current evidence on the clinical validity of DSM-5-APS, focusing on recent advances in diagnosis, prognosis, and treatment.

EVIDENCE REVIEW

A multistep literature search using the Web of Science database, Cochrane Central Register of Reviews, Ovid/PsychINFO, conference proceedings, and trial registries from database inception to June 16, 2019, was conducted following PRISMA and MOOSE guidelines and PROSPERO protocol. Studies with original data investigating individuals diagnosed using DSM-5-APS or meeting comparable criteria were included. The results of the systematic review were summarized in tables and narratively synthesized against established evidence-based antecedent, concurrent, and prognostic validators. A quantitative meta-analysis was conducted to explore the cumulative risk of psychosis onset at 6, 12, 24, and 36 months in individuals diagnosed using DSM-5-APS criteria.

FINDINGS

The systematic review included 56 articles, which reported on 124 validators, including 15 antecedent, 55 concurrent, and 54 prognostic validators. The epidemiological prevalence of the general non-help-seeking young population meeting DSM-5-APS criteria was 0.3%; the prevalence of individuals meeting DSM-5-APS criteria was variable in clinical samples. The interrater reliability for DSM-5-APS criteria was comparable with that of other DSM-5 mental disorders and can be optimized by the use of specific psychometric instruments. DSM-5-APS criteria were associated with frequent depressive comorbid disorders, distress, suicidality, and functional impairment. The meta-analysis included 23 prospective cohort studies, including 2376 individuals. The meta-analytical risk of psychosis onset was 11% at 6 months, 15% at 12 months, 20% at 24 months, and 23% at 36 months. Research into predisposing and precipitating epidemiological factors, neurobiological correlates, and effective treatments for DSM-5-APS criteria has been limited.

CONCLUSIONS AND RELEVANCE

Over recent years, DSM-5-APS criteria have received substantial concurrent and prognostic validation, mostly driven by research into the clinical high-risk state for psychosis. Precipitating and predisposing factors, neurobiological correlates, and effective treatments are undetermined to date.

Can high intensity interval training improve health outcomes among people with mental illness? A systematic review and preliminary meta-analysis of intervention studies across a range of mental illnesses

BACKGROUND

High intensity interval training (HIIT) may have beneficial effects among people with mental illnesses. The aim of this systematic review was to establish the benefits, safety and adherence of HIIT interventions across all categories of mental illness.

METHODS

Major databases were searched from inception to 18/2/2019 for intervention studies investigating HIIT among people with mental illnesses. Study quality was assessed via the PEDro scale, intervention characteristics were reported using the TIDier and CERT checklists and findings narratively summarised. A preliminary meta-analysis was undertaken where possible.

RESULTS

12 intervention studies, (including 7 RCTs), were included. Evidence suggested HIIT improved cardiorespiratory fitness (5/8 intervention studies,63%), anthropometric variables (3/4,75%), mental health outcomes (9/12, 75%), cardiovascular fitness (5/9,56%), physical fitness (1/1,100%) and motor skills (1/1,100%), compare to pre-training. The preliminary meta-analysis of pre-post changes found HIIT reduced depression severity (Standardised mean difference (SMD):-1.36 [95%CI-1.63;-1.089], p<0.0001) and possibly improved VO2max (SMD:0.18 [95%CI -0.02; 0.37], p = 0.08) in people with depression. HIIT increased High-Density-Lipoprotein (SMD:0.373 [95%CI 0.18; 0.57], p = 0.0002) and possibly reduced general psychopathology (SMD:-1.58 [95%CI -3.35; 0.18], p = 0.08) in people with schizophrenia-spectrum disorders. No acute injuries were reported, mean adherence to HIIT sessions ranged from 64-94%, and dropout ranged from 0--50%.

LIMITATIONS

Results were limited to a small number of low-to-moderate quality intervention studies.

CONCLUSION

These findings suggest HIIT may improve a range of physical and mental health outcomes among people with mental illnesses. Nonetheless, high-quality well-powered trials are needed to reaffirm these findings, and future research should address the seemingly high rate of dropout.

Current understandings of the trajectory and emerging correlates of cognitive impairment in bipolar disorder: An overview of evidence

OBJECTIVES

Cognitive dysfunction affects a significant proportion of people with bipolar disorder (BD), but the cause, trajectory and correlates of such dysfunction remains unclear. Increased understanding of these factors is required to progress treatment development for this symptom dimension.

METHODS

This paper provides a critical overview of the literature concerning the trajectories and emerging correlates of cognitive functioning in BD. It is a narrative review in which we provide a qualitative synthesis of current evidence concerning clinical, molecular, neural and lifestyle correlates of cognitive impairment in BD across the lifespan (in premorbid, prodromal, early onset, post-onset, elderly cohorts).

RESULTS

There is emerging evidence of empirical links between cognitive impairment and an increased inflammatory state, brain structural abnormalities and reduced neuroprotection in BD. However, evidence regarding the progressive nature of cognitive impairment is mixed, since consensus between different cross-sectional data is lacking and does not align to the outcomes of the limited longitudinal studies available. Increased recognition of cognitive heterogeneity in BD may help to explain some inconsistencies in the extant literature.

CONCLUSIONS

Large, longitudinally focussed studies of cognition and its covariation alongside biological and lifestyle factors are required to better define cognitive trajectories in BD, and eventually pave the way for the application of a precision medicine approach for individual patients in clinical practice.

Neurococognitive and neuroimaging correlates of obesity and components of metabolic syndrome in bipolar disorder: a systematic review

BACKGROUND

Individuals with bipolar disorder (BD) have a higher prevalence of obesity and metabolic syndrome (MetS) compared with the general population. Obesity and MetS are associated with cognitive deficits and brain imaging abnormalities in the general population. Obesity and components of MetS might potentially associate with neuroimaging and neurocognitive findings in BD.

METHODS

A literature search of studies investigating the association between obesity (and other components of MetS) and neurocognitive and neuroimaging findings in BD was conducted. In addition to a systematic review, a random-effects meta-analysis was conducted when sufficient data were available.

RESULTS

Twenty-three studies were included in the current systematic review. Overweight/obese patients were significantly associated with impaired neurocognition compared normal weight individuals with BD (d = 0.37). The most robust association between obesity and cognitive deficits in BD was observed in the cognitive subdomain of executive functions (d = 0.61). There was also evidence for a significant relationship between cognitive impairment in BD and other components of MetS including hypertension, dyslipidemia, and diabetes. Overweight/obese individuals with BD had more pronounced brain imaging abnormalities than normal weight individuals with BD.

CONCLUSIONS

Obesity and related cardiovascular risk factors significantly are associated with more severe cognitive and brain imaging abnormalities in BD. Medical co-morbidities can potentially contribute to functional decline observed in some patients throughout the course of BD.

EPA guidance on physical activity as a treatment for severe mental illness: a meta-review of the evidence and Position Statement from the European Psychiatric Association (EPA), supported by the International Organization of Physical Therapists in Mental Health (IOPTMH)

Physical activity (PA) may be therapeutic for people with severe mental illness (SMI) who generally have low PA and experience numerous life style-related medical complications. We conducted a meta-review of PA interventions and their impact on health outcomes for people with SMI, including schizophrenia-spectrum disorders, major depressive disorder (MDD) and bipolar disorder. We searched major electronic databases until January 2018 for systematic reviews with/without meta-analysis that investigated PA for any SMI. We rated the quality of studies with the AMSTAR tool, grading the quality of evidence, and identifying gaps, future research needs and clinical practice recommendations. For MDD, consistent evidence indicated that PA can improve depressive symptoms versus control conditions, with effects comparable to those of antidepressants and psychotherapy. PA can also improve cardiorespiratory fitness and quality of life in people with MDD, although the impact on physical health outcomes was limited. There were no differences in adverse events versus control conditions. For MDD, larger effect sizes were seen when PA was delivered at moderate-vigorous intensity and supervised by an exercise specialist. For schizophrenia-spectrum disorders, evidence indicates that aerobic PA can reduce psychiatric symptoms, improves cognition and various subdomains, cardiorespiratory fitness, whilst evidence for the impact on anthropometric measures was inconsistent. There was a paucity of studies investigating PA in bipolar disorder, precluding any definitive recommendations. No cost effectiveness analyses in any SMI condition were identified. We make multiple recommendations to fill existing research gaps and increase the use of PA in routine clinical care aimed at improving psychiatric and medical outcomes.

Differentiating between clinical and behavioral phenotypes in first-episode psychosis during maintenance of visuospatial working memory

INTRODUCTION

We probed the neural basis of working memory in individuals with first episode of psychosis (FEP) and assessed how these neural abnormalities are associated with behavioral performance and/or core to psychosis pathophysiology.

METHODS

FEP (N=35) and matched controls (N=25) performed a visuospatial working memory task during fMRI acquisition. We isolated neural activity during the maintenance period and examined neural activity within regions typically engaged during a working memory task. Functional connectivity estimates were derived using psychophysiological interaction analysis. We examined correlations between brain function and behavioral performance and clinical symptomatology.

RESULTS

FEP had reduced accuracy and slower reaction times compared to controls (p<0.05, q<0.05). During the maintenance period, FEP exhibited reduced right dorsolateral prefrontal cortex (DLPFC) activation compared to controls (p=0.007, q=0.01), even when behavioral performance was matched between groups (p=0.01, q=0.03). Unlike controls, FEP failed to show increased dorsal anterior cingulate (dACC) activity with increased load level (p=0.02, q=0.06). Compared to controls, FEP showed increased negative DLPFC-dACC coupling during the maintenance period (p=0.05). Increased DLPFC activation was significantly associated with greater negative symptoms (p<0.005, q=0.02), while greater dACC activation was significantly associated with better performance in FEP (p<0.05, q<0.17).

CONCLUSION

WM impairment in psychosis may be specific to abnormalities in the ability of frontal systems processing executive commands (DLPFC) and monitoring performance (dACC) during the maintenance of information. Our results add to accumulating evidence indicating that DLPFC abnormalities may be core to psychosis psychopathology. We also provide new insights regarding how DLPFC abnormalities may undermine dACC processing during the maintenance of information.

Is Schizophrenia a Disorder of Consciousness? Experimental and Phenomenological Support for Anomalous Unconscious Processing

Decades ago, several authors have proposed that disorders in automatic processing lead to intrusive symptoms or abnormal contents in the consciousness of people with schizophrenia. However, since then, studies have mainly highlighted difficulties in patients' conscious experiencing and processing but rarely explored how unconscious and conscious mechanisms may interact in producing this experience. We report three lines of research, focusing on the processing of spatial frequencies, unpleasant information, and time-event structure that suggest that impairments occur at both the unconscious and conscious level. We argue that focusing on unconscious, physiological and automatic processing of information in patients, while contrasting that processing with conscious processing, is a first required step before understanding how distortions or other impairments emerge at the conscious level. We then indicate that the phenomenological tradition of psychiatry supports a similar claim and provides a theoretical framework helping to understand the relationship between the impairments and clinical symptoms. We base our argument on the presence of disorders in the minimal self in patients with schizophrenia. The minimal self is tacit and non-verbal and refers to the sense of bodily presence. We argue this sense is shaped by unconscious processes, whose alteration may thus affect the feeling of being a unique individual. This justifies a focus on unconscious mechanisms and a distinction from those associated with consciousness.

Predictive value of premorbid IQ, negative symptoms, and age for cognitive and social functions in Japanese patients with schizophrenia: A study using the Japanese version of the Brief Assessment of Cognition in Schizophrenia

Enduring cognitive impairment in patients with schizophrenia represents a global health burden. The Japanese-language version of the Brief Assessment of Cognition in Schizophrenia (BACS) and the Japanese Adult Reading Test were administered to 288 patients with chronic schizophrenia and 308 unrelated healthy control subjects. The Japanese version of self-reported Social Functioning Scale (SFS) was administered to a subpopulation of 157 patients with schizophrenia. In patients with schizophrenia, premorbid IQ and age were significantly related to most of the BACS subdomains, composite score, and intra-individual variability of BACS subdomains, whereas negative symptoms were significantly related to all BACS indices. Dosages of the first-generation antipsychotics had a significant negative impact on Tower of London task and intra-individual variability of BACS subdomains. The relationship of symbol coding with age was significantly lower in patients than in healthy control subjects. Multiple regression analysis revealed that negative symptoms were significantly negatively related to the total SFS scale, whereas better performance of token motor task was associated with higher total SFS. The present study revealed the role of premorbid IQ, age, and negative symptoms in predicting cognitive performance, and the significant correlation of negative symptoms and token motor task with social function in patients with schizophrenia.

Psychotic Experiences and Working Memory: A Population-Based Study Using Signal-Detection Analysis

Psychotic Experiences (PEs) during adolescence index increased risk for psychotic disorders and schizophrenia in adult life. Working memory (WM) deficits are a core feature of these disorders. Our objective was to examine the relationship between PEs and WM in a general population sample of young people in a case control study. 4744 individuals of age 17–18 from Bristol and surrounding areas (UK) were analyzed in a cross-sectional study nested within the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort study. The dependent variable was PEs, assessed using the semi-structured Psychosis-Like Symptom Interview (PLIKSi). The independent variable was performance on a computerized numerical n-back working memory task. Signal-Detection Theory indices, including standardized hits rate, false alarms rate, discriminability index (d’) and response bias (c) from 2-Back and 3-Back tasks were calculated. 3576 and 3527 individuals had complete data for 2-Back and 3-Back respectively. Suspected/definite PEs prevalence was 7.9% (N = 374). Strongest evidence of association was seen between PEs and false alarms on the 2-Back, (odds ratio (OR) = 1.17 [95% confidence intervals (CI) 1.01, 1.35]) and 3-back (OR = 1.35 [1.18, 1.54]) and with c (OR = 1.59 [1.09, 2.34]), and lower d’ (OR = 0.76 [0.65, 0.89]), on the 3-Back. Adjustment for several potential confounders, including general IQ, drug exposure and different psycho-social factors, and subsequent multiple imputation of missing data did not materially alter the results. WM is impaired in young people with PEs in the general population. False alarms, rather than poor accuracy, are more closely related to PEs. Such impairment is consistent with different neuropsychological models of psychosis focusing on signal-to-noise discrimination, probabilistic reasoning and impaired reality monitoring as a basis of psychotic symptoms.

Early Adolescent Emergence of Reversal Learning Impairments in Isolation-Reared Rats

Cognitive impairments appear early in the progression of schizophrenia, often preceding the symptoms of psychosis. Thus, the systems subserving these functions may be more vulnerable to, and mechanistically linked with, the initial pathology. Understanding the trajectory of behavioral and anatomical abnormalities relevant to the schizophrenia prodrome and their sensitivity to interventions in relevant models will be critical to identifying early therapeutic strategies. Isolation rearing of rats is an environmental perturbation that deprives rodents of social contact from weaning through adulthood and produces behavioral and neuronal abnormalities that mirror some pathophysiology associated with schizophrenia, e.g. frontal cortex abnormalities and prepulse inhibition (PPI) of startle deficits. Previously, we showed that PPI deficits in isolation-reared rats emerge in mid-adolescence (4 weeks after weaning; approx. postnatal day 52) but are not present when tested at 2 weeks after weaning (approx. postnatal day 38). Because cognitive deficits are reported during early adolescence, are relevant to the prodrome, and are linked to functional outcome, we examined the putative time course of reversal learning deficits in isolation-reared rats. Separate groups of male Sprague Dawley rats were tested in a two-choice discrimination task at 2 and 8 weeks after weaning, on postnatal day 38 and 80, respectively. The isolation-reared rats displayed impaired reversal learning at both time points. Isolation rearing was also associated with deficits in PPI at 4 and 10 weeks after weaning. The reversal learning deficits in the isolated rats were accompanied by reductions in parvalbumin immunoreactivity, a marker for specific subpopulations of GABAergic neurons, in the hippocampus. Hence, isolation rearing of rats may offer a unique model to examine the ontogeny of behavioral and neurobiological alterations that may be relevant to preclinical models of prodromal psychosis. © 2015 S. Karger AG, Basel.