Neurobiological background of negative symptoms

Cognitive Inflexibility Predicts Negative Symptoms Severity in Patients with First-Episode Psychosis: A 1-Year Follow-Up Study

Negative symptoms and cognitive deficits play a major role in psychosis and significantly influence the functional outcomes of patients, particularly those with a first episode of psychosis (FEP). However, limited research has explored the predictive capacity of cognitive deficits during FEP for subsequent negative symptomatology. Drawing from the Athens FEP research study, we conducted a retrospective longitudinal study in 80 individuals with FEP. All patients were drug naive at admission. Cognitive tests were administered at 1-month and 1-year post-admission, while negative symptomatology was assessed at the same time points using PANSS by trained raters. We considered confounding factors such as age, gender, duration of untreated psychosis (DUP), treatment received, premorbid social adjustment, and premorbid IQ. Univariate regression analysis identified cognitive domains that correlated with negative symptomatology. These, along with the confounders, were incorporated into a multiple regression, with the 1-year PANSS negative scale serving as the dependent variable. Employing the backward elimination technique, we found a statistically significant inverse relationship between the categories completed in the Wisconsin card sorting test (WCST) and the 1-year PANNS negative scale (p = 0.01), beyond the associations with DUP and the 1-month PANSS negative scale. Our results suggest that cognitive flexibility, a key component of executive functions, predicts negative symptom severity one year after FEP.

Functional magnetic resonance imaging in schizophrenia: current evidence, methodological advances, limitations and future directions

Functional neuroimaging emerged with great promise and has provided fundamental insights into the neurobiology of schizophrenia. However, it has faced challenges and criticisms, most notably a lack of clinical translation. This paper provides a comprehensive review and critical summary of the literature on functional neuroimaging, in particular functional magnetic resonance imaging (fMRI), in schizophrenia. We begin by reviewing research on fMRI biomarkers in schizophrenia and the clinical high risk phase through a historical lens, moving from case-control regional brain activation to global connectivity and advanced analytical approaches, and more recent machine learning algorithms to identify predictive neuroimaging features. Findings from fMRI studies of negative symptoms as well as of neurocognitive and social cognitive deficits are then reviewed. Functional neural markers of these symptoms and deficits may represent promising treatment targets in schizophrenia. Next, we summarize fMRI research related to antipsychotic medication, psychotherapy and psychosocial interventions, and neurostimulation, including treatment response and resistance, therapeutic mechanisms, and treatment targeting. We also review the utility of fMRI and data-driven approaches to dissect the heterogeneity of schizophrenia, moving beyond case-control comparisons, as well as methodological considerations and advances, including consortia and precision fMRI. Lastly, limitations and future directions of research in the field are discussed. Our comprehensive review suggests that, in order for fMRI to be clinically useful in the care of patients with schizophrenia, research should address potentially actionable clinical decisions that are routine in schizophrenia treatment, such as which antipsychotic should be prescribed or whether a given patient is likely to have persistent functional impairment. The potential clinical utility of fMRI is influenced by and must be weighed against cost and accessibility factors. Future evaluations of the utility of fMRI in prognostic and treatment response studies may consider including a health economics analysis.

Structure/function interrelationships and illness insight in patients with schizophrenia: a multimodal MRI data fusion study

Illness insight in schizophrenia (SZ) has an important impact on treatment outcome, integration into society and can vary over the course of the disorder. To deal with and treat reduced or absent illness insight, we need to better understand its functional and structural correlates. Previous studies showed regionally abnormal brain volume in brain areas related to cognitive control and self-reference. However, little is known about associations between illness insight and structural and functional network strength in patients with SZ. This study employed a cross-sectional design to examine structural and functional differences between patients with SZ (n = 74) and healthy controls (n = 47) using structural and resting-state functional magnetic resonance imaging (MRI). Voxel-based morphometry was performed on structural data, and the amplitude of low frequency fluctuations (ALFF) was calculated for functional data. To investigate abnormal structure/function interrelationships and their association with illness insight, we used parallel independent component analysis (pICA). Significant group (SZ vs. HC) differences were detected in distinct structural and functional networks, predominantly comprising frontoparietal, temporal and cerebellar regions. Significant associations were found between illness insight and two distinct structural networks comprising frontoparietal (pre- and postcentral gyrus, inferior parietal lobule, thalamus, and precuneus) and posterior cortical regions (cuneus, precuneus, lingual, posterior cingulate, and middle occipital gyrus). Finally, we found a significant relationship between illness insight and functional network comprising temporal regions (superior temporal gyrus). This study suggests that aberrant structural and functional integrity of neural systems subserving cognitive control, memory and self-reference are tightly coupled to illness insight in SZ.

Dimensional characteristics of persistent negative symptoms in schizophrenia and their relationships with schizotypy in first-degree relatives

PURPOSE OF THE ARTICLE

Schizophrenia with persistent negative symptoms (PNS) may have different characteristics regarding negative symptom dimensions and heritability patterns. This study aimed to investigate the dimensional characteristics of PNS and their relationships with schizotypal features in first-degree relatives (FDRs).

MATERIALS AND METHODS

The study included 142 patients, 142 FDRs, and 71 healthy controls (HC). Patients were evaluated with the Positive and Negative Symptom Scale (PANSS), Brief Negative Symptom Scale (BNSS), Calgary Depression Scale for Schizophrenia (CDSS), and Simpson-Angus Scale (SAS). Schizotypy Personality Questionnaire was applied to FDR and HC groups. Clinical symptoms were compared between primary-PNS, secondary-PNS, and non-PNS groups. In addition, schizotypy scores were compared between FDRs and HCs. Then, the relationship between the symptoms of the patients in the PNS group and the schizotypy scores of their relatives was evaluated by multiple regression analysis.

RESULTS

All negative symptom dimension scores were similar in primary-PNS and secondary-PNS and lowest in non-PNS. PNS-FDR had higher in all schizotypy scores than non-PNS-FDR and HC, except for lack of close friends and social anxiety. In the PNS group, positive symptom severity and PANSS experiential deficit scores significantly predicted positive and negative schizotypy scores in relatives. Negative schizotypy was associated with asociality.

CONCLUSIONS

The PNS is likely a subtype in which the genetic basis of negative symptoms is stronger and is associated with genetic abnormalities shared by positive and negative schizotypy dimensions in relatives. Family-based genetic studies will be beneficial in enlightening the genetic etiology of PNS.

Resting-state perfusion in motor and fronto-limbic areas is linked to diminished expression of emotion and speech in schizophrenia

Negative symptoms (NS) are a core component of schizophrenia affecting community functioning and quality of life. We tested neural correlates of NS considering NS factors and consensus subdomains. We assessed NS using the Clinical Assessment Interview for Negative Symptoms and the Scale for Assessment of Negative Symptoms. Arterial spin labeling was applied to measure resting-state cerebral blood flow (rCBF) in 47 schizophrenia patients and 44 healthy controls. Multiple regression analyses calculated the relationship between rCBF and NS severity. We found an association between diminished expression (DE) and brain perfusion within the cerebellar anterior lobe and vermis, and the pre-, and supplementary motor area. Blunted affect was linked to fusiform gyrus and alogia to fronto-striatal rCBF. In contrast, motivation and pleasure was not associated with rCBF. These results highlight the key role of motor areas for DE. Considering NS factors and consensus subdomains may help identifying specific pathophysiological pathways of NS.

Effectiveness of accelerated intermittent theta burst stimulation for social cognition and negative symptoms among individuals with schizophrenia: A randomized controlled trial

BACKGROUND

Social cognitive and negative symptoms impairment may increase the risk of mental disability in individuals with schizophrenia. However, randomized controlled studies on the effectiveness of accelerated intermittent theta burst stimulation (iTBS) for social cognition and negative symptoms in individuals with schizophrenia are very limited.

METHODS

A total of 125 individuals with schizophrenia were recruited, 66 of whom were randomly divided into an active iTBS group (n=34) and sham iTBS group (n=32) by stratified sampling. Participants received either active iTBS or sham iTBS targeting the left dorsolateral prefrontal cortex (DLPFC) 20 sessions for 4 weeks under navigation. The Facial Emotion Recognition Test (FERT), Hinting Task (HT), and Positive and Negative Syndrome Scale (PANSS) were measured at baseline, 2 weeks, and 4 weeks. The trial protocol was registered with the Chinese Clinical Trial Registry (ChiCTR2100051984).

RESULTS

Sixty patients (90.90%) completed the intervention and the 4-week follow-up, including 29 women (43.94%) and 37 men (56.06%) with a mean (SD) age of 47.53 (10.17) years. The primary outcomes showed FERT scores (week 2; 0.27 [95% CI, 0.09 to 0.45]; P< .01; ES 0.14) (week 4; 0.63 [95% CI, 0.45 to 0.80]; P< .001; ES 0.47) and HT scores (week 2; 1.00 [95% CI, -0.02 to 1.98]; P< .05; ES 0.67) (week 4; 2.13 [95% CI, 1.21 to 3.06]; P< .001; ES 0.27) in the active iTBS group were significantly different from those in the sham iTBS group at 2 and 4 weeks of follow-up. The secondary outcome showed that the negative symptom score (-3.43 [95% CI, -4.85 to -2.01]; P< .001; ES 0.29) of the active iTBS group was significantly different from that of the sham iTBS group at the 4th week of follow-up.

CONCLUSIONS

Accelerated iTBS can effectively ameliorate the social cognition and negative symptoms of individuals with schizophrenia. These results suggest that accelerated iTBS may be a safe and effective neuromodulation technique to improve the overall functional recovery of individuals with schizophrenia, and has a good clinical application prospect.

Resting-State Brain Activity Dysfunctions in Schizophrenia and Their Associations with Negative Symptom Domains: An fMRI Study

The aim of the present study was to examine the neurobiological correlates of the two negative symptom domains of schizophrenia, the Motivational Deficit domain (including avolition, anhedonia, and asociality) and the Expressive Deficit domain (including blunted affect and alogia), focusing on brain areas that are most commonly found to be associated with negative symptoms in previous literature. Resting-state (rs) fMRI data were analyzed in 62 subjects affected by schizophrenia (SZs) and 46 healthy controls (HCs). The SZs, compared to the HCs, showed higher rs brain activity in the right inferior parietal lobule and the right temporoparietal junction, and lower rs brain activity in the right dorsolateral prefrontal cortex, the bilateral anterior dorsal cingulate cortex, and the ventral and dorsal caudate. Furthermore, in the SZs, the rs brain activity in the left orbitofrontal cortex correlated with negative symptoms (r = -0.436, p = 0.006), in particular with the Motivational Deficit domain (r = -0.424, p = 0.002), even after controlling for confounding factors. The left ventral caudate correlated with negative symptoms (r = -0.407, p = 0.003), especially with the Expressive Deficit domain (r = -0.401, p = 0.003); however, these results seemed to be affected by confounding factors. In line with the literature, our results demonstrated that the two negative symptom domains might be underpinned by different neurobiological mechanisms.

Methylation pattern and mRNA expression of synapse-relevant genes in the MAM model of schizophrenia in the time-course of adolescence

Schizophrenia is highly heritable and aggregating in families, but genetics alone does not exclusively explain the pathogenesis. Many risk factors, including childhood trauma, viral infections, migration, and the use of cannabis, are associated with schizophrenia. Adolescence seems to be the critical period where symptoms of the disease manifest. This work focuses on studying an epigenetic regulatory mechanism (the role of DNA methylation) and its interaction with mRNA expression during development, with a particular emphasis on adolescence. The presumptions regarding the role of aberrant neurodevelopment in schizophrenia were tested in the Methyl-Azoxy-Methanol (MAM) animal model. MAM treatment induces neurodevelopmental disruptions and behavioral deficits in off-springs of the treated animals reminiscent of those observed in schizophrenia and is thus considered a promising model for studying this pathology. On a gestational day-17, adult pregnant rats were treated with the antimitotic agent MAM. Experimental animals were divided into groups and subgroups according to substance treatment (MAM and vehicle agent [Sham]) and age of analysis (pre-adolescent and post-adolescent). Methylation and mRNA expression analysis of four candidate genes, which are often implicated in schizophrenia, with special emphasis on the Dopamine hypothesis i.e., Dopamine receptor D₂ (Drd2), and the "co-factors" Disrupted in schizophrenia 1 (DISC1), Synaptophysin (Syp), and Dystrobrevin-binding protein 1 (Dtnbp1), was performed in the Gyrus cingulum (CING) and prefrontal cortex (PFC). Data were analyzed to observe the effect of substance treatment between groups and the impact of adolescence within-group. We found reduced pre-adolescent expression levels of Drd2 in both brain areas under the application of MAM. The "co-factor genes" did not show high deviations in mRNA expression levels but high alterations of methylation rates under the application of MAM (up to ~20%), which diminished in the further time course, reaching a comparable level like in Sham control animals after adolescence. The pre-adolescent reduction in DRD2 expression might be interpreted as downregulation of the receptor due to hyperdopaminergic signaling from the ventral tegmental area (VTA), eventually even to both investigated brain regions. The notable alterations of methylation rates in the three analyzed co-factor genes might be interpreted as attempt to compensate for the altered dopaminergic neurotransmission.

Effects of bilateral, bipolar-nonbalanced, frontal transcranial Direct Current Stimulation (tDCS) on negative symptoms and neurocognition in a sample of patients living with schizophrenia: Results of a randomized double-blind sham-controlled trial

Negative symptoms (NS), conceived as Avolition-Apathy (AA) and Expressive Deficit (EXP) domains, and neurocognitive impairments represent unmet therapeutic needs for patients with schizophrenia. The present study investigated if bilateral bipolar-nonbalanced frontal transcranial Direct Current Stimulation (tDCS) could improve these psychopathological dimensions. This randomized, double-blind, sham-controlled study (active-tDCS versus sham-tDCS, both, n = 25) included 50 outpatients diagnosed with schizophrenia clinically stabilized. Patients received 20-min 2 mA active-tDCS or sham-tDCS (anode: left Dorsolateral Prefrontal Cortex; cathode: right orbitofrontal region). Primary outcomes included: PANSS-Negative subscale, Negative Factor (Neg-PANSS), AA and EXP domains; neurocognitive performance at Brief Assessment of Cognition in Schizophrenia. Secondary outcomes included: PANSS subscales and total score, Disorganized/Concrete (DiscC-PANSS) and Positive Factors, Clinical Global Impression (CGI) scores, clinical insight at Scale to Assess Unawareness of Mental Disorder (SUMD). Analysis of covariance (ANCOVA) was performed evaluating between-group changes over time. Significant improvements following active-tDCS were observed for all NS measures (all, p < 0.001; d > 0.8) and for working memory (p = 0.025, d = 0.31). Greater variations following to active treatment emerged also for PANSS-General Psychopathology subscale (p < 0.001; d = 0.54), PANSS total score (p < 0.001; d = 0.69), CGI indexes (all, p < 0.001; d > 0.6), DiscC-PANSS (p < 0.001; d = 0.80) and SUMD-general Unawareness index (p = 0.005; d = 0.15) but not for positive symptoms and others insight measures. Good safety/tolerability profiles were found. Bilateral bipolar-nonbalanced frontal-tDCS is a non-pharmacological approach in schizophrenia effectively improving NS, particularly the AA and EXP domains, probably acting by modulating dysfunctional cortical-subcortical networks. Preliminary results also suggest working memory improvements following tDCS. Further studies are needed to confirm the neurobiological basis of these results.

Peripheral inflammation levels associated with degree of advanced brain aging in schizophrenia

Brain structural abnormalities have been demonstrated in schizophrenia (SZ); these resemble those seen in typical aging, but are seen at younger ages. Furthermore, SZ is associated with accelerated global brain aging, as measured by brain structure-based brain predicted age difference (Brain-PAD). High heterogeneity exists in the degree of brain abnormalities in SZ, and individual differences may be related to levels of peripheral inflammation and may relate to cognitive deficits and negative symptoms. The goal of our study was to investigate the relationship between brain aging, peripheral inflammation, and symptoms of SZ. We hypothesized older brain-PAD in SZ vs. healthy comparison (HC) participants, as well as positive relationships of brain-PAD with peripheral inflammation markers and symptoms in SZ. We analyzed data from two cross-sectional studies in SZ (n = 26; M/F: 21/5) and HC (n = 28; 20/8) (22-64 years). Brain-PAD was calculated using a previously validated Gaussian process regression model applied to raw T1-weighted MRI data. Plasma levels of inflammatory biomarkers (CRP, Eotaxin, Fractalkine, IP10, IL6, IL10, ICAM1, IFNγ, MCP1, MIP1β, SAA, TNFα, VEGF, VCAM1) and cognitive and negative symptoms were assessed. We observed a higher brain-PAD in SZ vs. HC, and advanced brain age relative to chronological age was related to higher peripheral levels of TNFα in the overall group and in the SZ group; other inflammatory markers were not related to brain-PAD. Within the SZ group, we observed no association between cognitive or negative symptoms and brain-PAD. These results support our hypothesis of advanced brain aging in SZ. Furthermore, our findings on the relationship of the pro-inflammatory cytokine TNFα with higher brain-PAD of SZ are relevant to explain heterogeneity of brain ages in SZ, but we did not find strong evidence for cognitive or negative symptom relationships with brain-PAD.

Cluster analysis of negative symptoms identifies distinct negative symptom subgroups

The heterogeneity of schizophrenia has been acknowledged for decades because of the diverse presentation of symptoms, illness course, and treatment response noted between individuals diagnosed with the disorder. Cluster analysis has been used as a statistical method to determine whether schizophrenia subgroups might be identified based on symptom heterogeneity. However, there is very limited research examining whether heterogeneity in negative symptoms might be useful in establishing schizophrenia subtypes, particularly research examining newer models of negative symptoms based on five latent constructs including anhedonia, asociality, avolition, blunted affect, and alogia. The Brief Negative Symptom Scale was used to assess the five negative symptoms domains in a sample of 220 outpatients diagnosed with schizophrenia or schizoaffective disorder. Cluster analysis supported a four-cluster solution, comprising clusters of subjects with low negative symptoms (LNS), severe negative symptoms (SNS), and two clusters with moderate negative symptoms, one with predominantly elevated blunted affect (BA) and one with elevated avolition (AV). The LNS, SNS, BA, and AV clusters significantly differed on external validators including clinical characteristics, neurocognition, and functional outcome. Findings suggest that schizophrenia heterogeneity can be parsed according to negative symptom subtypes that have distinct clinical and neuropsychological profiles. Implications for diagnosis and treatment are discussed.

Medial temporal lobe and basal ganglia volume trajectories in persistent negative symptoms following a first episode of psychosis

BACKGROUND

Persistent negative symptoms (PNS, e.g., avolition, anhedonia, alogia) are present in up to 30% of individuals diagnosed with a first episode of psychosis and greatly impact functional outcomes. PNS and secondary PNS (sPNS: concomitant with positive, depressive, or extrapyramidal symptoms) may index distinct pathophysiologies reflected by structural brain changes, particularly in the medial temporal lobe (MTL) and basal ganglia.

AIMS

We sought to characterize dynamic brain changes related to PNS over the course of 2 years following a first episode of psychosis.

METHOD

Longitudinal volumetric trajectories within the MTL (hippocampus, parahippocampal gyrus, entorhinal cortex, perirhinal cortex) and basal ganglia (caudate, putamen, pallidum) were investigated in 98 patients with first-episode psychosis and 86 healthy controls using generalized estimating equations.

RESULTS

In left hippocampus, PNS (n = 25 at baseline) showed decreased volumes over time, sPNS (n = 26) volumes remained stable, and non-PNS (n = 47) volumes increased over time to control levels. PNS-specific changes were observed in left hippocampus and left perirhinal cortex, with the greatest decline from 12 to 24 months to levels significantly below those of non-PNS and controls. Affective/non-affective diagnosis, antipsychotic medication dosage and adherence at baseline did not significantly impact these findings. Basal ganglia volume trajectories did not distinguish between PNS and sPNS.

CONCLUSIONS

The current study highlights distinct structural brain trajectories in PNS that are prominent in the left MTL. Basal ganglia alterations may contribute to PNS irrespective of their etiology. Left MTL volume reductions were most evident after 1 year of treatment, highlighting the importance of targeted early interventions.

Dopaminergic dysfunction and excitatory/inhibitory imbalance in treatment-resistant schizophrenia and novel neuromodulatory treatment

Antipsychotic drugs are the mainstay in the treatment of schizophrenia. However, one-third of patients do not show adequate improvement in positive symptoms with non-clozapine antipsychotics. Additionally, approximately half of them show poor response to clozapine, electroconvulsive therapy, or other augmentation strategies. However, the development of novel treatment for these conditions is difficult due to the complex and heterogenous pathophysiology of treatment-resistant schizophrenia (TRS). Therefore, this review provides key findings, potential treatments, and a roadmap for future research in this area. First, we review the neurobiological pathophysiology of TRS, particularly the dopaminergic, glutamatergic, and GABAergic pathways. Next, the limitations of existing and promising treatments are presented. Specifically, this article focuses on the therapeutic potential of neuromodulation, including electroconvulsive therapy, repetitive transcranial magnetic stimulation, transcranial direct current stimulation, and deep brain stimulation. Finally, we propose multivariate analyses that integrate various perspectives of the pathogenesis, such as dopaminergic dysfunction and excitatory/inhibitory imbalance, thereby elucidating the heterogeneity of TRS that could not be obtained by conventional statistics. These analyses can in turn lead to a precision medicine approach with closed-loop neuromodulation targeting the detected pathophysiology of TRS.

Updated perspectives on the clinical significance of negative symptoms in patients with schizophrenia

INTRODUCTION

Negative symptoms in schizophrenia are associated with poor response to available treatments, poor quality of life, and functional outcome. Therefore, they represent a substantial burden for people with schizophrenia, their families, and health-care systems.

AREAS COVERED

In this manuscript, we will provide an update on the conceptualization, assessment, and treatment of this complex psychopathological dimension of schizophrenia.

EXPERT OPINION

Despite the progress in the conceptualization of negative symptoms and in the development of state-of-the-art assessment instruments made in the last decades, these symptoms are still poorly recognized, and not always assessed in line with current conceptualization. Every effort should be made to disseminate the current knowledge on negative symptoms, on their assessment instruments and available treatments whose efficacy is supported by research evidence. Longitudinal studies should be promoted to evaluate the natural course of negative symptoms, improve our ability to identify the different sources of secondary negative symptoms, provide effective interventions, and target primary and persistent negative symptoms with innovative treatment strategies. Further research is needed to identify pathophysiological mechanisms of primary negative symptoms and foster the development of new treatments.

The effects of catechol-O-methyltransferase single nucleotide polymorphisms on positive and negative symptoms of schizophrenia: A systematic review and meta-analysis

The catechol-O-methyltransferase (COMT) gene is thought to have an important role in the etiopathogenesis of schizophrenia, but there are conflicting results regarding its role in clinical presentation. We aimed to elucidate the relationship between the single nucleotide polymorphisms (SNPs) in the COMT gene and the severity of positive and negative symptoms. In order to investigate the relationship, the PubMed, PubMed Central, Scopus, and Cochrane CENTRAL databases were screened for eligible articles. Thirty-eight studies, including 4443 adult patients with schizophrenia, were included in the quantitative analyses, and four studies were qualitatively assessed. Quantitative analyses were performed for acutely ill and clinically stable patient subgroups regarding the different genotypes of rs4680 SNP. Our results showed that the severity of negative symptoms was higher in patients who were rs4680 Met homozygous compared to Val/Met heterozygotes only in acutely ill samples. There was no other significant difference between genotypes. Meta-regression did not reveal any significant moderator effect on the difference in negative symptoms. General psychopathology, positive, negative, and total psychotic symptom levels also were similar between Val homozygotes and Met carriers. Nonetheless, there are some limitations in the study. First, SNPs except for rs4680 were under-researched because of the limited number of studies. Second, high heterogeneity across studies was the main concern. Our results suggested that the COMT rs4680 Met allele was associated with higher levels of negative symptoms within acutely ill patients. Future studies should focus on specific patient subgroups to reveal the moderating effects of SNPs.

Serum BDNF levels, glycolipid metabolism in deficit schizophrenia: A case-control study

BACKGROUND

Few studies have compared serum BDNF and glycolipid profiles in patients with deficit schizophrenia (DS) and non-deficit schizophrenia (NDS). We aimed to compare BDNF and glycolipid profiles between DS and NDS patients and healthy controls, and to investigate the relationship between BDNF, glycolipid profiles in DS and NDS patients.

METHODS

A total of 591 patients with chronic schizophrenia (SZ) and 238 healthy controls participated in this study. According to Proxy for the Deficit Syndrome Scale, SZ patients were divided into DS (n = 158) and NDS (n = 273) patients. Psychiatric symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). Serum BDNF levels were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

BDNF levels were significantly lower in SZ patients than those in healthy controls (7.81 ± 2.98 ng/ml vs. 11.96 ± 2.29 ng/ml, P < 0.01). Furthermore, BDNF levels were lower in DS group than those in NDS group (P = 0.007, OR = 0.846, 95% CI = 0.750-0.955). Lower triglyceride levels were also an independent predictor for DS patients (P = 0.007, OR = 0.846, 95% CI = 0.750-0.955). Serum BDNF levels were negatively associated with the severity of deficit syndrome in SZ patients (β = -1.151, t = -2.559, P = 0.011). In DS group, triglycerides were associated with PANSS negative subscore (β = -0.262, t = -2.994, P = 0.003) and depressive factor subscore (β = 0.282, t = 2.146, P = 0.035).

CONCLUSION

Serum BDNF and triglycerides may be informative biomarkers of DS in SZ patients. The differences in glycolipid metabolism patterns between DS and NDS patients indicate that deficit syndrome is an independent endophenotype of SZ patients.

Two Factors, Five Factors, or Both? External Validation Studies of Negative Symptom Dimensions in Schizophrenia

OBJECTIVES

Negative symptom studies frequently use single composite scores as indicators of symptom severity and as primary endpoints in clinical trials. Factor analytic and external validation studies do not support this practice but rather suggest a multidimensional construct. The current study used structural equation modeling (SEM) to compare competing dimensional models of negative symptoms to determine the number of latent dimensions that best capture variance in biological, psychological, and clinical variables known to have associations with negative symptoms.

METHODS

Three independent studies (total n = 632) compared unidimensional, two-factor, five-factor, and hierarchical conceptualizations of negative symptoms in relation to cognition, psychopathology, and community functioning (Study 1); trait emotional experience and defeatist performance beliefs (Study 2); and glutamate and gamma-aminobutyric acid levels in the anterior cingulate cortex quantified using proton magnetic resonance spectroscopy (Study 3).

RESULTS

SEM favored the five-factor and hierarchical models over the unidimensional and two-factor models regardless of the negative symptom measure or external validator. The five dimensions-anhedonia, asociality, avolition, blunted affect, and alogia-proved vital either as stand-alone domains or as first-order domains influenced by second-order dimensions-motivation and pleasure and emotional expression. The two broader dimensions sometimes masked important associations unique to the five narrower domains. Avolition, anhedonia, and blunted affect showed the most domain-specific associations with external variables across study samples.

CONCLUSIONS

Five domains and a hierarchical model reflect the optimal conceptualization of negative symptoms in relation to external variables. Clinical trials should consider using the two dimensions as primary endpoints and the five domains as secondary endpoints.

Negative symptoms in alcohol use disorder: A pilot study applying the two-factor model of negative symptoms to patients with alcohol use disorder

BACKGROUND AND AIMS

Alcohol Use Disorder (AUD) is characterized by a reduction in goal-directed behavior, with alcohol use taking precedence over other areas of life. These features in AUD resemble negative symptoms in schizophrenia, especially the reduction in motivation and pleasure (MAP). Given the clinical similarities of negative symptoms across diagnostic categories, it comes as a surprise that there are few investigations on negative symptoms in alcohol and other substance use disorders. To our knowledge, our study is the first to assess negative symptoms in AUD based on a two-factorial approach, and to investigate the interrelation of these dimensions with the severity of AUD, and alcohol craving.

MATERIALS AND METHODS

We examined a sample of 42 patients with AUD at the Psychiatric University Hospital in Zurich. Participants provided self-report and interview-based measures of the severity of AUD, negative symptoms, and alcohol craving. Finally, we used data from the electronic health records of the patients.

RESULTS

Patients with AUD show negative symptoms to a similar extent as patients with schizophrenia or bipolar disorder. We found a positive correlation between the extent of impairment within the MAP factor and overall severity of AUD. Furthermore, MAP negative symptoms were correlated with alcohol craving. In a linear regression, negative symptoms predicted alcohol craving whereas depression did not.

SUMMARY

Negative symptoms as conceptualized for schizophrenia are prevalent in patients with AUD and associated with the severity of AUD. More specifically, severity of AUD correlates with diminished motivation and pleasure, highlighting the importance of disturbances in motivational functions in AUD. This is further supported by the correlation between negative symptoms and craving, a hallmark of AUD. Taken together, our findings suggest that negative symptoms might be a highly relevant but hitherto often neglected therapeutic target in AUD.

A Literature Mini-Review of Transcranial Direct Current Stimulation in Schizophrenia

Transcranial direct current stimulation (tDCS) is a non-invasive neurostimulation method that utilizes the effect of low-current on brain tissue. In recent years, the effect of transcranial direct current stimulation has been investigated as a therapeutic modality in various neuropsychiatric indications, one of them being schizophrenia. This article aims to provide an overview of the potential application and effect of tDCS in treating patients with schizophrenia. A literature search was performed using the PubMed, Web of Science, and Google Scholar databases for relevant research published from any date until December 2021. Eligible studies included those that used randomized controlled parallel-group design and focused on the use of transcranial direct current stimulation for the treatment of positive, negative, or cognitive symptoms of schizophrenia. Studies were divided into groups based on the focus of research and an overview is provided in separate sections and tables in the article. The original database search yielded 705 results out of which 27 randomized controlled trials met the eligibility criteria and were selected and used for the purpose of this article. In a review of the selected trials, transcranial direct current stimulation is a safe and well-tolerated method that appears to have the potential as an effective modality for the treatment of positive and negative schizophrenic symptoms and offers promising results in influencing cognition. However, ongoing research is needed to confirm these conclusions and to further specify distinct application parameters.

Corpus callosum in schizophrenia with deficit and non-deficit syndrome: a statistical shape analysis

Background

The corpus callosum (CC) is the most targeted region in the cerebrum that integrates cognitive data between homologous areas in the right and left hemispheres.

Aims

Our study used statistical analysis to determine whether there was a correlation between shape changes in the CC in patients with schizophrenia (SZ) (deficit syndrome (DS) and non-deficit syndrome (NDS)) and healthy control (HC) subjects.

Methods

This study consisted of 27 HC subjects and 50 schizophrenic patients (20 with DS and 30 with NDS). 3 patients with DS and 4 patients with NDS were excluded. Three-dimensional, sagittal, T1-spoiled, gradient-echo imaging was used. Standard anatomical landmarks were selected and marked on each image using specific software.

Results

As to comparing the Procrustes mean shapes of the CC, statistically significant differences were observed between HC and SZ (DS+NDS) (p=0.017, James’s F_j=73.732), HC and DS (p<0.001, James’s F_j=140.843), HC and NDS (p=0.006, James’s F_j=89.178) and also DS and NDS (p<0.001, James’s F_j=152.967). Shape variability in the form of CC was 0.131, 0.085, 0.082 and 0.086 in the HC, SZ (DS+NDS), DS and NDS groups, respectively.

Conclusions

This study reveals callosal shape variations in patients with SZ and their DS and NDS subgroups that take into account the CC’s topographic distribution.

Investigating the Relationship between White Matter Connectivity and Motivational Circuits in Subjects with Deficit Schizophrenia: A Diffusion Tensor Imaging (DTI) Study

Deficit schizophrenia is a subtype of schizophrenia presenting primary and enduring negative symptoms (NS). Although one of the most updated hypotheses indicates a relationship between NS and impaired motivation, only a few studies have investigated abnormalities of motivational circuits in subjects with deficit schizophrenia (DS). Our aim was to investigate structural connectivity within motivational circuits in DS. We analyzed diffusion tensor imaging (DTI) data from 46 subjects with schizophrenia (SCZ) and 35 healthy controls (HCs). SCZ were classified as DS (n = 9) and non-deficit (NDS) (n = 37) using the Schedule for Deficit Syndrome. The connectivity index (CI) and the Fractional Anisotropy (FA) of the connections between selected brain areas involved in motivational circuits were examined. DS, as compared with NDS and HCs, showed increased CI between the right amygdala and dorsal anterior insular cortex and increased FA of the pathway connecting the left nucleus accumbens with the posterior insular cortex. Our results support previous evidence of distinct neurobiological alterations underlying different clinical subtypes of schizophrenia. DS, as compared with NDS and HCs, may present an altered pruning process (consistent with the hyperconnectivity) in cerebral regions involved in updating the stimulus value to guide goal-directed behavior.

Pars Triangularis Volume Asymmetry and Schneiderian First Rank Symptoms in Antipsychotic-naïve Schizophrenia

Objective

Schizophrenia is a disorder of language and self, with first-rank symptoms (FRS) as one of the predominant features in a subset of patients. Abnormal language lateralization is hypothesized to underlie the neurobiology of FRS in schizophrenia. The role of Broca's area with its right-hemispheric counterpart, consisting of pars triangularis (PTr) and pars opercularis (POp) of the inferior frontal gyrus in FRS is undetermined. We compared the volumes and asymmetries of PTr & POp in anti-psychotic-naive schizophrenia patients with FRS (FRS[＋]) with those without FRS (FRS[-]) and healthy-controls (HC) using three dimensional, interactive, semi-automated volumetric morphometry.

Methods

Antipsychotic naïve FRS(＋) (n = 27), FRS(-) (n = 24) and HC (n = 51) were carefully assessed with structured and semi-structured clinical tools. T1-weighted images were acquired in a 3T scanner. Volumes of regions of interest were measured independently for both sides using slicer-3D software, and asymmetry indices were calculated.

Results

FRS(＋) but not FRS(-) had a significant volume deficit in right PTr after controlling for the potential confounding effects of age, sex, and intracranial volume (p = 0.029). There was a significant leftward asymmetry of PTr in patients with FRS (i.e., leftward asymmetry in patients) (p = 0.026). No significant volume/asymmetry abnormalities were observed in POp.

Conclusion

Study findings suggest reduced right PTr volume with leftward asymmetry to be associated with FRS in schizophrenia. This is consistent with the loss of Yakovlevian torque in schizophrenia. Role of PTr in the neurobiology of schizophrenia as a disorder of self, speech, and social cognition needs further systematic evaluation in future research.

Review and meta-analysis of add-on tranylcypromine with antipsychotic drugs for the treatment of schizophrenia with predominant negative symptoms: a restoration of evidence

BACKGROUND

Treatment using add-on antidepressants with antipsychotic drugs in negative symptoms of schizophrenia has been reviewed recently in comprehensive meta-analyses. Tranylcypromine (TCP), an irreversible monoamine oxidase (MAO)-A/B inhibitor applied in treatment resistant depression, was not included because of strict requirements for quality of study design. To get a clear picture of available evidence for this resource in the treatment of schizophrenia, we conducted a review and meta-analysis of add-on TCP in the treatment of predominant negative symptoms of schizophrenia (negative schizophrenia).

METHODS

Seven controlled studies of add-on TCP in schizophrenia with predominant negative symptoms were found in a search of multiple databases. A subset of four studies of the prospective and parallel comparison of add-on TCP with antipsychotic drugs vs. antipsychotic drug monotherapy and meeting minimum quality criteria formed the primary meta-analysis. The effect size was calculated as the natural logarithm of the odds ratio (logOR) of responders and non-responders.

RESULTS

In the primary meta-analysis, a pooled logOR = 1.092 with 95%CI 0.410-1.774 (I² = 43.4%, moderate heterogeneity) was calculated according to a fixed-effect model. Heterogeneity was reduced for three double-blind studies of add-on TCP with trifluoperazine (TFP) vs. TFP-monotherapy and resulted a pooled logOR = 0.916 with 95%CI 0.216-1.616 (I² negative, no heterogeneity). A significant logOR = 1.558 with 95%CI 0.340-2.776 was found for TCP/TFP compared to placebo in one study. In a meta-analysis of extrapyramidal adverse effects, studies were very heterogeneous and revealed no significant differences between treatments. The risk of exacerbation of positive symptoms with add-on TCP was found to be very low for a duration of treatment of 12-16 weeks. No cases of hypertensive crisis were reported. The main methodical limitations were insufficient description of randomization or matching of patients without randomization. The main clinical limitation is a gap of data for add-on TCP with second-generation antipsychotics.

CONCLUSION

New studies are needed for add-on TCP with antipsychotic drugs in schizophrenia with predominant negative symptoms. Trials of this treatment may be possible in rare and selected cases. The therapeutic effect of add-on TCP may be explained by a strong dopaminergic activity.

Global hypomyelination of the brain white and gray matter in schizophrenia: quantitative imaging using macromolecular proton fraction

Myelin deficiency is commonly recognized as an important pathological feature of brain tissues in schizophrenia (SZ). In this pilot study, global myelin content abnormalities in white matter (WM) and gray matter (GM) of SZ patients were non-invasively investigated using a novel clinically-targeted quantitative myelin imaging technique, fast macromolecular proton fraction (MPF) mapping. MPF maps were obtained from 23 healthy subjects and 31 SZ patients using a clinical 1.5T magnetic resonance imaging (MRI) scanner. Mean MPF in WM and GM was compared between the healthy control subjects and SZ patients with positive and negative leading symptoms using the multivariate analysis of covariance. The SZ patients had significantly reduced MPF in GM (p < 0.001) and WM (p = 0.02) with the corresponding relative decrease of 5% and 3%, respectively. The effect sizes for the myelin content loss in SZ relative to the control group were 1.0 and 1.5 for WM and GM, respectively. The SZ patients with leading negative symptoms had significantly lower MPF in GM (p < 0.001) and WM (p = 0.003) as compared to the controls and showed a significant MPF decrease in WM (p = 0.03) relative to the patients with leading positive symptoms. MPF in WM significantly negatively correlated with the disease duration in SZ patients (Pearson's r = -0.51; p = 0.004). This study demonstrates that chronic SZ is characterized by global microscopic brain hypomyelination of both WM and GM, which is associated with the disease duration and negative symptoms. Myelin deficiency in SZ can be detected and quantified by the fast MPF mapping method.

Neurocognitive functions in persistent negative symptoms following a first episode of psychosis

Negative symptoms are present at the onset of psychosis and their persistence is significantly associated with poor psychosocial functioning and lower quality of life. Persistent negative symptoms (PNS) may be idiopathic or secondary to other factors such as depression, positive symptoms, and medication side-effects. Several studies have examined neurocognitive functions in early psychosis patients with PNS relative to non-PNS, but have not systematically controlled for secondary PNS (sPNS). The latter may have a distinct neurocognitive profile that could obscure differences between PNS and non-PNS. Using a large (n = 425) sample, we examined neurocognitive functions in PNS, sPNS, and non-PNS and hypothesized that PNS would be associated with greater impairments relative to non-PNS. Following admission to an early intervention program, a neurocognitive battery was administered after at least 3 months of treatment, and symptom data collected during a subsequent 6-month period were used to classify patients as PNS, sPNS and non-PNS. At month 12, both PNS and sPNS groups had significantly lower level of functioning relative to the non-PNS group but the sPNS group experienced higher levels of depressive and positive symptoms and were on a higher dose of antipsychotics. Relative to non-PNS, PNS patients exhibited significant impairments in verbal memory and working memory, whereas sPNS patients exhibited a trend towards greater impairments in verbal memory. This study confirms that the presence of PNS or sPNS negatively influences functioning with more selective cognitive impairments found in PNS, providing evidence that these groups of patients could benefit from different personalised interventions.

Association of Candidate Single Nucleotide Polymorphisms Related to Candidate Genes in Patients With Schizophrenia

Introduction:

Schizophrenia is a chronic heterogenic neurodevelopment disorder. Many genes interfere in the development of SCZ. All four genes, NrCAM, PRODH, ANK3, and ANKK1, which were evaluated in this study, were previously reported to be associated with Schizophrenia. The NrCAM contributes to creating cognitive deficiencies through the CAM’s signaling pathway. PRODH plays a vital role in creating SCZ negative symptoms through the signaling pathway of glutamatergic and NMDA receptors. ANK3 affects ion channel and molecular adhesion in Ranvier and initial segments of axons, leading to mental retardation, sleep disorder, and SCZ. ANKK1 encodes a protein kinase and was reported to be associated with alcohol addiction, Attention Deficit Hyperactivity Disorder (ADHD), and SCZ.

Methods:

The subjects were selected from Schizophrenic patients referring to the Psychiatric Ward of Imam-Hussein Hospital and Schizophrenic Patients Support Institution (AHEBBA). 95 (30 Schizoaffective patients, 57 Paranoid patients, and 8 disorganized) patients were recruited as the subjects in the present case-control association study. 120 healthy subjects were recruited from the Tehran Medical Genetics Laboratory staff and a group of students from the Islamic Azad University of Science and Research in Tehran. The genotypes were determined with molecular genotyping techniques of PCR-RFLP, ARMS-PCR, and Cycle sequencing. Results were analyzed by the Chi-Square test using SPSS V. 24 and R, SNP STATE Package to investigate significant differences between cases and controls.

Results:

The incidence of schizophrenia was 68% and 32% among men and women, respectively. The evaluation of the allelic association between schizophrenia and all the candidate SNPs showed a significant association between NrCAM’s SNP rs10235968 and SCZ (P=0.001). Haplotype T, T, C in rs10235968, rs6967368, rs3763463, respectively, within the NrCAM gene, showed significant association with schizophrenia disorder (P=0.0001).

Conclusion:

No association was found between other candidate SNPs and SCZ among the subjects.

Intermittent theta burst stimulation for negative symptoms of schizophrenia-A double-blind, sham-controlled pilot study

Optimal noninvasive brain stimulation parameters for the treatment of negative symptoms of schizophrenia remain unclear. Here, we aimed to investigate the clinical and biological effects of intermittent theta burst transcranial magnetic stimulation (iTBS) in patients with treatment-resistant negative symptoms of schizophrenia (NCT00875498). In a randomized sham-controlled 2-arm study, 22 patients with schizophrenia and treatment-resistant negative symptoms received 20 sessions of either active (n = 12) or sham (n = 10) iTBS. Sessions were delivered twice a day on 10 consecutive working days. Negative symptom severity was assessed 5 times using the Scale for the Assessment of Negative Symptoms (SANS): before iTBS, after iTBS, and 1, 3, and 6 months after iTBS. As a secondary objective, we explored the acute effects of iTBS on functional connectivity of the left dorsolateral prefrontal cortex (DLPFC) using seed-based resting-state functional connectivity MRI (rsFC fMRI) images acquired before and after iTBS. Active iTBS over the left DLPFC significantly decreased negative symptoms severity compared to sham iTBS (F_(3,60) = 3.321, p = 0.026). Post hoc analyses revealed that the difference between groups was significant 6 months after the end of stimulation sessions. Neuroimaging revealed an increase in rsFC between the left DLPFC and a brain region encompassing the right lateral occipital cortex and right angular gyrus and a right midbrain region that may encompass dopamine neuron cell bodies. Thus, iTBS over the left DLPFC can alleviate negative symptoms of schizophrenia. The effect might be driven by significant modulation of dopamine transmission.

Neuroanatomy of Patients with Deficit Schizophrenia: An Exploratory Quantitative Meta-Analysis of Structural Neuroimaging Studies

Little is known regarding the neuroanatomical correlates of patients with deficit schizophrenia or persistent negative symptoms. In this meta-analysis, we aimed to determine whether patients with deficit schizophrenia have characteristic brain abnormalities. We searched PubMed, CINAHL and Ovid to identify studies that examined the various regions of interest amongst patients with deficit schizophrenia, patients with non-deficit schizophrenia and healthy controls. A total of 24 studies met our inclusion criteria. A random-effects model was used to calculate a combination of outcome measures, and heterogeneity was assessed by the I² statistic and Cochran’s Q statistic. Our findings suggested that there was statistically significant reduction in grey matter volume (−0.433, 95% confidence interval (CI): −0.853 to −0.014, p = 0.043) and white matter volume (−0.319, 95% CI: −0.619 to −0.018, p = 0.038) in patients with deficit schizophrenia compared to healthy controls. There is also statistically significant reduction in total brain volume (−0.212, 95% CI: −0.384 to −0.041, p = 0.015) and white matter volume (−0.283, 95% CI: −0.546 to −0.021, p = 0.034) in patients with non-deficit schizophrenia compared to healthy controls. Between patients with deficit and non-deficit schizophrenia, there were no statistically significant differences in volumetric findings across the various regions of interest.

Intersection of verbal memory and expressivity on cortical contrast and thickness in first episode psychosis

BACKGROUND

Longitudinal studies of first episode of psychosis (FEP) patients are critical to understanding the dynamic clinical factors influencing functional outcomes; negative symptoms and verbal memory (VM) deficits are two such factors that remain a therapeutic challenge. This study uses white-gray matter contrast at the inner edge of the cortex, in addition to cortical thickness, to probe changes in microstructure and their relation with negative symptoms and possible intersections with verbal memory.

METHODS

T1-weighted images and clinical data were collected longitudinally for patients (N = 88) over a two-year period. Cognitive data were also collected at baseline. Relationships between baseline VM (immediate/delayed recall) and rate of change in two negative symptom dimensions, amotivation and expressivity, were assessed at the behavioral level, as well as at the level of brain structure.

RESULTS

VM, particularly immediate recall, was significantly and positively associated with a steeper rate of expressivity symptom decline (r = 0.32, q = 0.012). Significant interaction effects between baseline delayed recall and change in expressivity were uncovered in somatomotor regions bilaterally for both white-gray matter contrast and cortical thickness. Furthermore, interaction effects between immediate recall and change in expressivity on cortical thickness rates were uncovered across higher-order regions of the language processing network.

CONCLUSIONS

This study shows common neural correlates of language-related brain areas underlying expressivity and VM in FEP, suggesting deficits in these domains may be more linked to speech production rather than general cognitive capacity. Together, white-gray matter contrast and cortical thickness may optimally inform clinical investigations aiming to capture peri-cortical microstructural changes.

Frontal white matter abnormalities reveal the pathological basis underlying negative symptoms in antipsychotic-naïve, first-episode patients with adolescent-onset schizophrenia: Evidence from multimodal brain imaging

A major challenge in schizophrenia is to uncover the pathophysiological basis of its negative symptoms. Recent neuroimaging studies revealed that disrupted structural properties of frontal white matter (FWM) are associated with the negative symptoms of schizophrenia. However, there is little direct functional evidence of FWM for negative symptoms in schizophrenia. To address this issue, we combined resting-state connectome-wide functional connectivity (FC) and diffusion tensor imaging tractography to investigate the alteration of FWM underlying the negative symptoms in 39 drug-naive patients with adolescent-onset schizophrenia (AOS) and 31 age- and sex- matched healthy controls (HCs). Results revealed that the intrinsic FC and structural properties (fraction anisotropy and fibers) of the left FWM correspond to individual negative symptoms in AOS. Moreover, the serotonin network (raphe nuclei, anterior and posterior cingulate cortices, and prefrontal and inferior parietal cortices) and FWM-cingulum network were found to contributed to the negative symptom severity in AOS. Furthermore, the patients showed abnormal functional and structural connectivities between the interhemispheric FWM compared with HCs. Importantly, the decreased fiber counts between the interhemispheric FWM were inversely correlated with the negative symptoms in AOS. Our findings demonstrated the association between FWM and negative symptoms, and offered initial evidence by using WM connectome to uncover WM functional information in schizophrenia.

Association of family history of schizophrenia and history of obstetric complications at birth: relationship with age at onset and psychopathology dimensions in a Nigerian cohort

Background

The nature of the association between obstetric complications (OCs) at birth and the genetic aetiology of schizophrenia remains unclear, as some authors suggest that it is an independent risk factor while others support either interactionism or an epiphenomenon perspective.

Objective

To examine the association of family history of schizophrenia (FHS) with history of OCs, with a view to assessing whether this relationship moderates clinical phenotypes such as symptom dimensions and age at onset of illness.

Methods

This study examined OCs among schizophrenia probands using the Obstetric Complications Scale. An inquiry into family history was performed using the Family history method. Psychopathological symptom dimensions were assessed using standard scales. Data were analyzed to examine the interaction of FHS and history of OCs with age at onset and symptom dimensions, using ANCOVA.

Results

FHS was significantly associated with the disorganized symptoms dimension (p=0.03). History of OCs was significantly associated with earlier age at onset (p=0.007). However, in ANCOVA, the effect of the interaction between FHS and history of OCs was not significant for age at onset and symptom dimensions (P = 0.059).

Conclusion

FHS was significantly associated with disorganization syndrome, and OCs was significantly associated with age at onset.

Associations between schizophrenia polygenic risk and apathy in schizophrenia spectrum disorders and healthy controls

OBJECTIVE

Apathy is a central predictor of a poor functional outcome in schizophrenia. Schizophrenia polygenic risk scores (PRSs) are used to detect genetic associations to key clinical phenotypes in schizophrenia. We explored the associations between schizophrenia PRS and apathy levels in schizophrenia spectrum disorders (n = 281) and matched healthy controls (n = 298), and further how schizophrenia PRS contributed in predicting apathy when added to premorbid and clinical factors in the patient sample.

METHOD

Schizophrenia PRSs were computed for each participant. Apathy was assessed with the Apathy Evaluation Scale. Bivariate correlation analyses were used to investigate associations between schizophrenia PRS and apathy, and between apathy and premorbid and clinical factors. Multiple hierarchical regression analyses were employed to evaluate the contributions of clinical variables and schizophrenia PRS to apathy levels.

RESULTS

We found no significant associations between schizophrenia PRS and apathy in patients and healthy controls. Several premorbid and clinical characteristics significantly predicted apathy in patients, but schizophrenia PRS did not.

CONCLUSION

Since the PRSs are based on common genetic variants, our results do not preclude associations to other types of genetic factors. The results could also indicate that environmentally based biological or psychological factors contribute to apathy levels in schizophrenia.

Association of the brain-derived neurotrophic factor Val66Met polymorphism with negative symptoms severity, but not cognitive function, in first-episode schizophrenia spectrum disorders

Objective

A functional polymorphism of the brain-derived neurotrophic factor gene (BDNF) Val66Met has been associated with cognitive function and symptom severity in patients with schizophrenia. It has been suggested that the Val66Met polymorphism has a role as a modulator in a range of clinical features of the illness, including symptoms severity, therapeutic responsiveness, age of onset, brain morphology and cognitive function. However, little work has been done in first-episode schizophrenia (FES) spectrum disorders. The objective of this study is to investigate the association of the BDNF Val66Met polymorphism on cognitive function and clinical symptomatology in FES patients.

Methods

Using a cross-sectional design in a cohort of 204 patients with FES or a schizophrenia spectrum disorder and 204 healthy matched controls, we performed BDNF Val66Met genotyping and tested its relationship with cognitive testing (attention, working memory, learning/verbal memory and reasoning/problem-solving) and assessment of clinical symptom severity.

Results

There was no significant influence of the BDNF allele frequency on cognitive factor scores in either patients or controls. An augmented severity of negative symptoms was found in FES patients that carried the Met allele.

Conclusions

The results of this study suggest that in patients with a first-episode of schizophrenia or a schizophrenia spectrum disorder, the BDNF Val66Met polymorphism does not exert an influence on cognitive functioning, but is associated with negative symptoms severity. BDNF may serve as suitable marker of negative symptomatology severity in FES patients within the schizophrenia spectrum.

Modulating NMDA receptors to treat MK-801-induced schizophrenic cognition deficit: effects of clozapine combining with PQQ treatment and possible mechanisms of action

BACKGROUND

Clozapine has remarkable efficacy on both negative and cognitive symptoms of schizophrenia due to its slight activation of NMDA receptor. In fact, much evidence to the contrary. NMDAR is a complex containing specific binding sites, which are regulated to improve negative symptoms and cognitive deficits associated with individuals affected by schizophrenia. PQQ is a powerful neuroprotectant that specifically binds with NMDA receptors in the brain to produce beneficial physiological and cognitive outcomes. The aim of this study was to enhance NMDAR function and improve cognitive ability in schizophrenia by PQQ combined with clozapine.

METHODS

Rats were divided into four groups (n = 5) including control (saline), model (MK-801, 0.5 mg·kg^- 1·d^- 1), atypical antipsychotic (MK-801 (0.5 mg·kg^- 1·d^- 1) + Clozapine (1.0 mg·kg^- 1·d^- 1), and co-agonist NMDA receptor (MK-801 (0.5 mg·kg^- 1·d^- 1) + Clozapine (0.5 mg·kg^- 1·d^- 1) + PQQ (1.0 μg·kg^- 1·d^- 1) group. Each group of rats was injected subcutaneously every day for 6 weeks. Behavior test, including stereotyped behavior, locomotor hyperactivity, learning and memory, was performed. The Western blot assay was performed to analyze the expression of GSK-3β, Akt, NMDAR1, and MGLUR in rat hippocampus.

RESULTS

Results indicated that clozapine and PQQ combination therapy can improve MK801-induced schizophrenia behavior including stereotyped behavior, locomotor hyperactivity and cognitive impairment. Furthermore, we found that modulating NMDA receptors could ameliorate the memory impairments in Mk-801 induced schizophrenia rats by reducing the expression of NMDAR1 and MGLUR3, decreasing hippocampal tau hyperphosphorylation and inhibiting apoptosis through Akt /GSK-3β signaling pathway.

CONCLUSIONS

These findings suggest that combination therapy for enhancing NMDA receptors may be able to rescue cognition deficit in schizophrenia. More studies are needed to better elucidate these mechanisms.

Plasma Levels of Neuron- and Astrocyte-Derived Exosomal Amyloid Beta1-42, Amyloid Beta1-40, and Phosphorylated Tau Levels in Schizophrenia Patients and Non-psychiatric Comparison Subjects: Relationships With Cognitive Functioning and Psychopathology

Introduction: Cognitive deficits in people with schizophrenia (PWS) are a major predictor of disability and functioning, yet the underlying pathophysiology remains unclear. A possible role of amyloid and tau biomarkers (hallmarks of Alzheimer's disease) is still speculative in schizophrenia. Exosomes or extracellular vesicles, involved with cell-to-cell communication and waste removal, can be used to assay brain-based proteins from peripheral blood. To our knowledge, this is the first study of exosomal amyloid and tau protein levels in PWS. Methods: This cross-sectional study included 60 PWS and 60 age- and sex-comparable non-psychiatric comparison subjects (NCs), age range 26-65 years. Assessments of global cognitive screening, executive functioning, psychopathology, and physical measures were conducted. Exosomes were extracted and precipitated from fasting plasma and identified as neuron-derived exosomes (NDEs) or astrocyte-derived exosomes (ADEs). Human-specific ELISAs were used to assay levels of amyloid-beta 1-42 (Aβ42), amyloid-beta 1-40 (Aβ40), and phosphorylated T181 tau (P-T181-tau). Plasma assays for aging biomarkers (C-reactive protein and F2-isoprostanes) were also performed. Results: ADE-Aβ42 levels were higher in PWS compared to NCs, though the other exosomal markers were similar between the two groups. Higher ADE-P-T181-tau levels were associated with worse executive functioning. Among PWS, higher ADE-P-T181-tau levels were associated with less severe negative symptoms and increased F2-isoprostane levels. Astrocyte-derived Aβ marker levels were sensitive and specific in differentiating between diagnostic groups. Among PWS, Aβ40 levels differed most by exosomal origin. Discussion: Exosomal markers may provide novel insights into brain-based processes (e.g., aging, oxidative stress) from peripheral blood samples.

Reduced mu opioid receptor availability in schizophrenia revealed with [11C]-carfentanil positron emission tomographic Imaging

Negative symptoms, such as amotivation and anhedonia, are a major cause of functional impairment in schizophrenia. There are currently no licensed treatments for negative symptoms, highlighting the need to understand the molecular mechanisms underlying them. Mu-opioid receptors (MOR) in the striatum play a key role in hedonic processing and reward function and are reduced post-mortem in schizophrenia. However, it is unknown if mu-opioid receptor availability is altered in-vivo or related to negative symptoms in schizophrenia. Using [¹¹C]-carfentanil positron emission tomography (PET) scans in 19 schizophrenia patients and 20 age-matched healthy controls, here we show a significantly lower MOR availability in patients with schizophrenia in the striatum (Cohen's d = 0.7), and the hedonic network. In addition, we report a marked global increase in inter-regional covariance of MOR availability in schizophrenia, largely due to increased cortical-subcortical covariance.

Antipsychotics: Mechanisms underlying clinical response and side-effects and novel treatment approaches based on pathophysiology

Antipsychotic drugs are central to the treatment of schizophrenia and other psychotic disorders but are ineffective for some patients and associated with side-effects and nonadherence in others. We review the in vitro, pre-clinical, clinical and molecular imaging evidence on the mode of action of antipsychotics and their side-effects. This identifies the key role of striatal dopamine D2 receptor blockade for clinical response, but also for endocrine and motor side-effects, indicating a therapeutic window for D2 blockade. We consider how partial D2/3 receptor agonists fit within this framework, and the role of off-target effects of antipsychotics, particularly at serotonergic, histaminergic, cholinergic, and adrenergic receptors for efficacy and side-effects such as weight gain, sedation and dysphoria. We review the neurobiology of schizophrenia relevant to the mode of action of antipsychotics, and for the identification of new treatment targets. This shows elevated striatal dopamine synthesis and release capacity in dorsal regions of the striatum underlies the positive symptoms of psychosis and suggests reduced dopamine release in cortical regions contributes to cognitive and negative symptoms. Current drugs act downstream of the major dopamine abnormalities in schizophrenia, and potentially worsen cortical dopamine function. We consider new approaches including targeting dopamine synthesis and storage, autoreceptors, and trace amine receptors, and the cannabinoid, muscarinic, GABAergic and glutamatergic regulation of dopamine neurons, as well as post-synaptic modulation through phosphodiesterase inhibitors. Finally, we consider treatments for cognitive and negative symptoms such dopamine agonists, nicotinic agents and AMPA modulators before discussing immunological approaches which may be disease modifying. This article is part of the issue entitled 'Special Issue on Antipsychotics'.

Persistent negative symptoms in individuals at Ultra High Risk for psychosis

Persistent negative symptoms (PNS) defined as negative symptoms that persist for at least six months in the absence of high levels of positive, depressive and extrapyramidal symptoms, are evident early in the course of schizophrenia from the first episode of psychosis. However, their presence even earlier in the illness, in those at Ultra High Risk of psychosis, has not been investigated. In this study, we examined the prevalence, baseline correlates and outcome of PNS in 363 Ultra High Risk individuals. Assessments were conducted at baseline and 2-14 years later (mean follow up time 7.4 years). Baseline assessments included demographic, clinical and neurocognitive measures, which were repeated at follow up. The prevalence of PNS in the UHR group was 6.1%. Poor premorbid social adjustment, deficits in verbal fluency and childhood maltreatment, specifically emotional neglect, were evident at baseline in the PNS group compared to the group without PNS. PNS were associated with poor psychosocial functioning and deficits in processing speed at follow up. Our findings suggest that PNS can be detected early, allowing for the identification of a subset of Ultra High Risk patients who are likely to have poor outcome. These individuals could be the target for specific intervention. Further research is needed into the pathophysiology of these PNS to develop specific interventions.

MK212, a 5-hydroxytryptamine 2C receptor agonist, inhibits conditioned avoidance responses independent of blocking endogenous dopamine release in rats

Although it is widely accepted that 5-hydroxytryptamine (5-HT) 2C receptor agonists produce antipsychotic effects by reducing endogenous dopamine release from presynaptic neurons, no direct evidence supports this. The aim of the present study was to investigate whether the antipsychotic effects induced by 5-HT_2C receptor agonists are dependent on the inhibition of endogenous dopamine release. We developed a novel conditioned avoidance response paradigm to test this hypothesis. In this assay, rats in which dopamine was depleted by reserpine failed to show conditioned avoidance responses, and the acute administration of quinpirole reversed the disruption of avoidance responses induced by reserpine. This suggests that animals successfully showed conditioned avoidance responses independent of endogenous dopamine release under these experimental conditions. Our results revealed that MK212 (0.5 mg/kg) reduced avoidance responses triggered by quinpirole in dopamine-depleted rats. Therefore, 5-HT_2C receptor agonists can inhibit conditioned avoidance responses independent of blocking endogenous dopamine release. Furthermore, the 5-HT_2C receptor agonist, MK212, decreased the extracellular concentration of glutamate in the nucleus accumbens, indicating that this mechanism may be critical for the antipsychotic effects of 5-HT_2C receptor agonists.

Schizophrenia, Not a Psychotic Disorder: Bleuler Revisited

Current diagnostic criteria delineate schizophrenia as a discrete entity essentially defined by positive symptoms. However, the role of positive symptoms in psychiatry is being questioned. There is compelling evidence that psychotic manifestations are expressed in the population in a continuum of varying degrees of severity, ranging from normality to full-blown psychosis. In most cases, these phenomena do not persist, but they constitute risk factors for psychiatric disorders in general. Psychotic symptoms are also present in most non-psychotic psychiatric diagnoses, being a marker of severity. Research revealed that hallucinations and delusions appear to have distinct, independent biological underpinnings-in the general population, in psychotic, and in non-psychotic disorders as well. On the other hand, negative symptoms were seen to be far more restricted to schizophrenia, have other underlying pathophysiology than positive symptoms, predict outcome and treatment response in schizophrenia, and start before the first psychotic outbreak. The current work discusses the concept of schizophrenia, suggesting that a greater emphasis should be put on cases where psychotic symptoms emerge in a premorbid subtly increasing negative/cognitive symptoms background. In those cases, psychosis would have a different course and outcome while psychosis occurring in the absence of such background deterioration would be more benign-probably having no, or a milder, underlying degenerative process. This reformulation should better drive psychopathological classification, face positive symptoms as epiphenomenon of the schizophrenia process, and dishevel stigma from schizophrenia and from delusions and hallucinations.

Potential Role of Antipsychotic-Galantamine-Memantine Combination in the Treatment of Positive, Cognitive, and Negative Symptoms of Schizophrenia

Schizophrenia is, in part, a cognitive illness. There are no approved medications for cognitive impairments associated with schizophrenia (CIAS) and primary negative symptoms. Cholinergic and glutamatergic systems, alpha-7 nicotinic acetylcholine (α-7nACh) and N-methyl-D-aspartate (NMDA) receptors, kynurenic acid (KYNA), and mismatch negativity have been implicated in the pathophysiology of CIAS and negative symptoms. Galantamine is an acetylcholinesterase inhibitor that is also a positive allosteric modulator at the α4β2 and α7nACh receptors. Memantine is a noncompetitive NMDA receptor antagonist. Galantamine and memantine alone and in combination were effective for cognition in animals and people with Alzheimer's disease. The objective of this article is to critically dissect the published randomized controlled trials with galantamine and memantine for CIAS to highlight the efficacy signal. These studies may have failed to detect a clinically meaningful efficacy signal due to limitations, methodological issues, and possible medication nonadherence. There is evidence from a small open-label study that the galantamine-memantine combination may be effective for CIAS with kynurenine pathway metabolites as biomarkers to detect the severity of cognitive impairments. Given that there are no available treatments for cognitive impairments and primary negative symptoms in schizophrenia, testing of this "five-pronged strategy" (quintuple hypotheses: dopamine, nicotinic-cholinergic, glutamatergic/NMDA, GABA, and KYNA) is a "low-risk high-gain" approach that could be a major breakthrough in the field. The galantamine-memantine combination has the potential to treat positive, cognitive, and negative symptoms, and targeting the quintuple hypotheses concurrently may lead to a major scientific advancement - from antipsychotic treatment to antischizophrenia treatment.

Negative symptoms, anxiety, and depression as mechanisms of change of a 12-month trial of assertive community treatment as part of integrated care in patients with first- and multi-episode schizophrenia spectrum disorders (ACCESS I trial)

Assertive community treatment (ACT) has shown to be effective in improving both functional deficits and quality of life (QoL) in patients with severe mental illness. However, the mechanisms of this beneficial effect remained unclear. We examined mechanisms of change by testing potential mediators including two subdomains of negative symptoms, i.e. social amotivation as well as expressive negative symptoms, anxiety, and depression within a therapeutic ACT model (ACCESS I trial) in a sample of 120 first- and multi-episode patients with a schizophrenia spectrum disorder (DSM-IV). Path modelling served to test the postulated relationship between the respective treatment condition, i.e. 12-month ACT as part of integrated care versus standard care, and changes in functioning and QoL. The final path model resulted in 3 differential pathways that were all significant. Treatment-induced changes in social amotivation served as a starting point for all pathways, and had a direct beneficial effect on functioning and an additional indirect effect on it through changes in anxiety. Expressive negative symptoms were not related to functioning but served as a mediator between changes in social amotivation and depressive symptoms, which subsequently resulted in improvements in QoL. Our results suggest that social amotivation, expressive negative symptoms, depression, and anxiety functioned as mechanisms of change of ACCESS. An integrated and sequential treatment focusing on these mediators may optimise the generalisation effects on functioning as well as on QoL by targeting the most powerful mechanism of change that fits best to the individual patient.

Neurophysiological correlates of Avolition-apathy in schizophrenia: A resting-EEG microstates study

Background

The “Avolition-apathy” domain of the negative symptoms was found to include different symptoms by factor analytic studies on ratings derived by different scales. In particular, the relationship of anhedonia with this domain is controversial. Recently introduced negative symptom rating scales provide a better assessment of anhedonia, allowing the distinction of anticipatory and consummatory aspects, which might be related to different psychopathological dimensions. The study of associations with external validators, such as electrophysiological, brain imaging or cognitive indices, might shed further light on the status of anhedonia within the Avolition-apathy domain.

Objectives

We used brain electrical microstates (MSs), which represent subsecond periods of quasi-stable scalp electrical field, associated with resting-state neural networks (and thus with global patterns of functional connectivity), to test whether the component symptoms of Avolition-apathy share the same correlates.

Method

We analyzed multichannel resting EEGs in 142 individuals with schizophrenia (SCZ) and in 64 healthy controls (HC), recruited within the add-on EEG study of the Italian Network for Research on Psychoses. Relative time contribution, duration and occurrence of four MS classes (MS-A/-B/-C/−D) were calculated. Group differences on MS parameters (contribution and duration) and their associations with negative symptom domains (assessed using the Brief Negative Symptoms Scale) were investigated.

Results

SCZ, in comparison to HC, showed increased contribution and duration of MS-C. The contribution of MS-A positively correlated with Avolition-apathy, but not with Expressive deficit. Within the Avolition-apathy domain, anticipatory anhedonia, avolition and asociality, but not consummatory anhedonia, showed the same correlations with MS-A contribution.

Conclusion

Our findings support the existence of distinct electrophysiological correlates of Avolition-apathy with respect to Expressive deficit, and lend support to the hypothesis that only the anticipatory component of anhedonia shares the same pathophysiological underpinnings of the Avolition-apathy domain.

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Microstate C contribution and duration were increased in SCZ compared to HC.

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Avolition-apathy was correlated with the contribution of microstate A.

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Avolition-apathy might be associated with sensory processing deficit.

Functional connectivity of the ventral tegmental area and avolition in subjects with schizophrenia: a resting state functional MRI study

Avolition, a deficit in goal-directed behavior, is a key aspect of negative symptoms. It is highly prevalent in schizophrenia and is associated to poor functional outcome and to measures of real life motivation, indicating that central to the concept is the lack of interest and motivation. In this study we tested the hypothesis that avolition is related to altered connectivity within dopaminergic cortico-striatal circuits involved in motivation processes. Since dopamine input to these circuits derives mostly from the ventro-tegmental area (VTA), we investigated the relationships between the resting-state functional connectivity (RS-FC) of the VTA and avolition in twenty-six subjects with schizophrenia (SCZ), treated with second-generation antipsychotics only, compared to twenty-two healthy controls (HC). SCZ, in comparison to HC, showed significantly reduced RS-FC of the VTA with bilateral ventro-lateral prefrontal cortex (VLPFC), bilateral insular cortex (IC) and right (R) lateral occipital complex (LOC) and increased RS-FC of the VTA with bilateral dorso-lateral prefrontal cortex (DLPFC). Significant negative correlations were found between avolition and RS-FC of the VTA with the bilateral IC, R VLPFC and R LOC. According to our findings, avolition is linked to a disconnectivity of the VTA from several key cortical regions involved in the integration of value information with action selection. These findings are in line with translational animal models of "auto-activation apathy".

Relationship Between Persistent Negative Symptoms and Findings of Neurocognition and Neuroimaging in Schizophrenia

Negative symptoms are defined as loss or reduction of otherwise present behaviors or functions in illness situation, and they have constituted an important aspect of schizophrenia. Although negative symptoms have usually been considered as a single entity, neurobiological investigations yielded discrepant results. To overcome challenges that derive from this discrepancy, researchers have proposed several approaches to structure negative symptoms into more homogenous constructs. Concept of persistent negative symptoms (PNS) is one of the proposed approaches, and includes both primary and secondary negative symptoms that persist after adequate treatment. PNS is relatively easy to assess, and by definition, more inclusive; yet it represents an unmet therapeutic need. Therefore, it is a target of several neurobiological and pharmacological studies. There are several structural and functional brain alterations associated with negative symptoms. On the other hand, neurocognitive investigations in patients with schizophrenia have revealed deficits in several domains that showed correlations with negative symptoms. There are several shared features between negative symptoms and neurocognitive deficits in schizophrenia such as prevalence rates, course through the illness, prognostic importance, and impact on social functioning. However, exact mechanisms behind the neurobiology of PNS and how it interacts with neurocognition remain to be explained. Earlier reviews on neuroimaging and neurocognitive correlates of PNS have been focused on studies with broadly defined negative symptoms that were selected by methodological closeness to PNS. In this review, we focus on neural correlates and neurocognitive associations of PNS, and we discuss PNS findings available to date.