Dopaminergic basis of salience dysregulation in psychosis

The underlying neurobiological basis of gray matter volume alterations in schizophrenia with auditory verbal hallucinations: A meta-analytic investigation

Schizophrenia patients with auditory verbal hallucinations (AVH) frequently exhibit brain structural alterations, particularly reductions in gray matter volume (GMV).Understanding the neurobiological mechanisms underlying the changes is essential for advancing treatment strategies. To address this, a meta-analysis was conducted to identify GMV changes in schizophrenia patients with AVH and their associations with gene expression and neurotransmitter receptor profiles. The results indicated significant GMV reductions in the left and the right insula, as well as the left anterior cingulate cortex. Ontology analysis of genes associated with GMV alternations revealed enrichment in biological processes related to ion transport and synaptic transmission. Hub genes from the KCN, SCN, GN, and PRK families, along with neurotransmitter receptors such as D2, VAChT, and mGluR5, showed significant correlations with GMV changes. Furthermore, multivariate linear regression analysis demonstrated that GNB2, GNB4, PRKCG, D2, and mGluR5 significantly predicted GMV alternations. These findings suggest that GMV reductions in schizophrenia with AVH are linked to disruptions in neurobiological processes involving specific genes and neurotransmitter systems, highlighting the potential targets for therapeutic intervention.

Identifying neurobiological heterogeneity in clinical high-risk psychosis: a data-driven biotyping approach using resting-state functional connectivity

To explore the neurobiological heterogeneity within the Clinical High-Risk (CHR) for psychosis population, this study aimed to identify and characterize distinct neurobiological biotypes within CHR using features from resting-state functional networks. A total of 239 participants from the Shanghai At Risk for Psychosis (SHARP) program were enrolled, consisting of 151 CHR individuals and 88 matched healthy controls (HCs). Functional connectivity (FC) features that were correlated with symptom severity were subjected to the single-cell interpretation through multikernel learning (SIMLR) algorithm in order to identify latent homogeneous subgroups. The cognitive function, clinical symptoms, FC patterns, and correlation with neurotransmitter systems of biotype profiles were compared. Three distinct CHR biotypes were identified based on 646 significant ROI-ROI connectivity features, comprising 29.8%, 19.2%, and 51.0% of the CHR sample, respectively. Despite the absence of overall FC differences between CHR and HC groups, each CHR biotype demonstrated unique FC abnormalities. Biotype 1 displayed augmented somatomotor connection, Biotype 2 shown compromised working memory with heightened subcortical and network-specific connectivity, and Biotype 3, characterized by significant negative symptoms, revealed extensive connectivity reductions along with increased limbic-subcortical connectivity. The neurotransmitter correlates differed across biotypes. Biotype 2 revealed an inverse trend to Biotype 3, as increased neurotransmitter concentrations improved functional connectivity in Biotype 2 but reduced it in Biotype 3. The identification of CHR biotypes provides compelling evidence for the early manifestation of heterogeneity within the psychosis spectrum, suggesting that distinct pathophysiological mechanisms may underlie these subgroups.

Distinguished Frontal White Matter Abnormalities Between Psychotic and Nonpsychotic Bipolar Disorders in a Pilot Study

BACKGROUND/OBJECTIVES

Recent studies indicate extensive shared white matter (WM) abnormalities between bipolar disorder (BD) and schizophrenia (SZ). However, the heterogeneity of WM in BD in terms of the presence of psychosis remains a critical issue for exploring the boundaries between BD and SZ. Previous studies comparing WM microstructures in psychotic and nonpsychotic BDs (PBD and NPBD) have resulted in limited findings, probably due to subtle changes, emphasizing the need for further investigation.

METHODS

Diffusion tensor imaging measures were obtained from 8 individuals with PBD, 8 with NPBD, and 22 healthy controls (HC), matched for age, gender, handedness, and educational years. Group comparisons were conducted using tract-based spatial statistics (TBSS). The most significant voxels showing differences between PBD and HC in the TBSS analyses were defined as a TBSS-ROI and subsequently analyzed.

RESULTS

Increased radial diffusivity (RD) in PBD compared to NPBD (p < 0.006; d = 1.706) was observed in TBSS-ROI, distributed in the confined regions of some WM tracts, including the body of the corpus callosum (bCC), the left genu of the CC (gCC), and the anterior and superior corona radiata (ACR and SCR). Additionally, NPBD exhibited significant age-associated RD increases (R2 = 0.822, p < 0.001), whereas the greater RD observed in PBD compared to NPBD remained consistent across middle age.

CONCLUSIONS

Preliminary findings from this small sample suggest severe frontal WM disconnection in the anterior interhemispheric communication, left fronto-limbic circuits, and cortico-striatal-thalamic loop in PBD compared to NPBD. While these results require replication and validation in larger and controlled samples, they provide insights into the pathophysiology of PBD, which is diagnostically located at the boundary between BD and SZ.

Task-based default mode network connectivity predicts cognitive impairment and negative symptoms in first-episode schizophrenia

Individuals diagnosed with schizophrenia (SZ) demonstrate difficulty distinguishing between internally and externally generated stimuli. These aberrations in "source monitoring" have been theorized as contributing to symptoms of the disorder, including hallucinations and delusions. Altered connectivity within the default mode network (DMN) of the brain has been proposed as a mechanism through which discrimination between self-generated and externally generated events is disrupted. Source monitoring abnormalities in SZ have additionally been linked to impairments in selective attention and inhibitory processing, which are reliably observed via the N100 component of the event-related brain potential elicited during an auditory paired-stimulus paradigm. Given overlapping constructs associated with DMN connectivity and N100 in SZ, the present investigation evaluated relationships between these measures of disorder-related dysfunction and sought to clarify the nature of task-based DMN function in SZ. DMN connectivity and N100 measures were assessed using EEG recorded from SZ during their first episode of illness (N = 52) and demographically matched healthy comparison participants (N = 25). SZ demonstrated less evoked theta-band connectivity within DMN following presentation of pairs of identical auditory stimuli than HC. Greater DMN connectivity among SZ was associated with better performance on measures of sustained attention (p = .03) and working memory (p = .09), as well as lower severity of negative symptoms, though it was not predictive of N100 measures. Together, present findings provide EEG evidence of lower task-based connectivity among first-episode SZ, reflecting disruptions of DMN functions that support cognitive processes. Attentional processes captured by N100 appear to be supported by different neural mechanisms.

Robust and replicable functional brain signatures of 22q11.2 deletion syndrome and associated psychosis: a deep neural network-based multi-cohort study

A major genetic risk factor for psychosis is 22q11.2 deletion (22q11.2DS). However, robust and replicable functional brain signatures of 22q11.2DS and 22q11.2DS-associated psychosis remain elusive due to small sample sizes and a focus on small single-site cohorts. Here, we identify functional brain signatures of 22q11.2DS and 22q11.2DS-associated psychosis, and their links with idiopathic early psychosis, using one of the largest multi-cohort data to date. We obtained multi-cohort clinical phenotypic and task-free fMRI data from 856 participants (101 22q11.2DS, 120 idiopathic early psychosis, 101 idiopathic autism, 123 idiopathic ADHD, and 411 healthy controls) in a case-control design. A novel spatiotemporal deep neural network (stDNN)-based analysis was applied to the multi-cohort data to identify functional brain signatures of 22q11.2DS and 22q11.2DS-associated psychosis. Next, stDNN was used to test the hypothesis that the functional brain signatures of 22q11.2DS-associated psychosis overlap with idiopathic early psychosis but not with autism and ADHD. stDNN-derived brain signatures distinguished 22q11.2DS from controls, and 22q11.2DS-associated psychosis with very high accuracies (86-94%) in the primary cohort and two fully independent cohorts without additional training. Robust distinguishing features of 22q11.2DS-associated psychosis emerged in the anterior insula node of the salience network and the striatum node of the dopaminergic reward pathway. These features also distinguished individuals with idiopathic early psychosis from controls, but not idiopathic autism or ADHD. Our results reveal that individuals with 22q11.2DS exhibit a highly distinct functional brain organization compared to controls. Additionally, the brain signatures of 22q11.2DS-associated psychosis overlap with those of idiopathic early psychosis in the salience network and dopaminergic reward pathway, providing substantial empirical support for the theoretical aberrant salience-based model of psychosis. Collectively, our findings, replicated across multiple independent cohorts, advance the understanding of 22q11.2DS and associated psychosis, underscoring the value of 22q11.2DS as a genetic model for probing the neurobiological underpinnings of psychosis and its progression.

Unveiling altered connectivity between cognitive networks and cerebellum in schizophrenia

Cognitive functioning is a crucial aspect in schizophrenia (SZ), and when altered it has devastating effects on patients' quality of life and treatment outcomes. Several studies suggested that they could result from altered communication between the cortex and cerebellum. However, the neural correlates underlying these impairments have not been identified. In this study, we investigated resting state functional connectivity (rsFC) in SZ patients, by considering the interactions between cortical networks supporting cognition and cerebellum. In addition, we investigated the relationship between SZ patients' rsFC and their symptoms. We used fMRI data from 74 SZ patients and 74 matched healthy controls (HC) downloaded from the publicly available database SchizConnect. We implemented a seed-based connectivity approach to identify altered functional connections between specific cortical networks and cerebellum. We considered ten commonly studied resting state networks, whose functioning encompasses specific cognitive functions, and the cerebellum, whose involvement in supporting cognition has been recently identified. We then explored the relationship between altered rsFC values and Positive and Negative Syndrome Scale (PANSS) scores. The SZ group showed increased connectivity values compared with HC group for cortical networks involved in attentive processes, which were also linked to PANSS items describing attention and language-related processing. We also showed decreased connectivity between cerebellar regions, and increased connectivity between them and attentive networks, suggesting the contribution of cerebellum to attentive and affective deficits. In conclusion, our findings highlighted the link between negative symptoms in SZ and altered connectivity within the cerebellum and between the same and cortical networks supporting cognition.

NMDAR dysfunction and the regulation of dopaminergic transmission in schizophrenia

A substantial body of evidence implicates dysfunction in N-methyl-d-aspartate receptors (NMDARs) in the pathophysiology of schizophrenia. This article illustrates how NMDAR dysfunction may give rise to many of the neurobiological phenomena frequently associated with schizophrenia with a particular focus on how NMDAR dysfunction affects the thalamic reticular nucleus (nRT) and pedunculopontine tegmental nucleus (PPTg). Furthermore, this article presents a model for schizophrenia illustrating how dysfunction in the nRT may interrupt prefrontal regulation of midbrain dopaminergic neurons, and how dysfunction in the PPTg may drive increased, irregular burst firing.

Predictive Processing: A Circuit Approach to Psychosis

Predictive processing is a computational framework that aims to explain how the brain processes sensory information by making predictions about the environment and minimizing prediction errors. It can also be used to explain some of the key symptoms of psychotic disorders such as schizophrenia. In recent years, substantial advances have been made in our understanding of the neuronal circuitry that underlies predictive processing in cortex. In this review, we summarize these findings and how they might relate to psychosis and to observed cell type-specific effects of antipsychotic drugs. We argue that quantifying the effects of antipsychotic drugs on specific neuronal circuit elements is a promising approach to understanding not only the mechanism of action of antipsychotic drugs but also psychosis. Finally, we outline some of the key experiments that should be done. The aims of this review are to provide an overview of the current circuit-based approaches to psychosis and to encourage further research in this direction.

What Remains to Be Discovered in Schizophrenia Therapeutics: Contributions by Advancing the Molecular Mechanisms of Drugs for Psychosis and Schizophrenia

Schizophrenia is a frequently debilitating and complex mental disorder affecting approximately 1% of the global population, characterized by symptoms such as hallucinations, delusions, disorganized thoughts and behaviors, cognitive dysfunction, and negative symptoms. Traditional treatment has centered on postsynaptic dopamine antagonists, commonly known as antipsychotic drugs, which aim to alleviate symptoms and improve functioning and the quality of life. Despite the availability of these medications, significant challenges remain in schizophrenia therapeutics, including incomplete symptom relief, treatment resistance, and medication side effects. This opinion article explores advancements in schizophrenia treatment, emphasizing molecular mechanisms, novel drug targets, and innovative delivery methods. One promising approach is novel strategies that target neural networks and circuits rather than single neurotransmitters, acknowledging the complexity of brain region interconnections involved in schizophrenia. Another promising approach is the development of biased agonists, which selectively activate specific signaling pathways downstream of receptors, offering potential for more precise pharmacological interventions with fewer side effects. The concept of molecular polypharmacy, where a single drug targets multiple molecular pathways, is exemplified by KarXT, a novel drug combining xanomeline and trospium to address both psychosis and cognitive dysfunction. This approach represents a comprehensive strategy for schizophrenia treatment, potentially improving outcomes for patients. In conclusion, advancing the molecular understanding of schizophrenia and exploring innovative therapeutic strategies hold promise for addressing the unmet needs in schizophrenia treatment, aiming for more effective and tailored interventions. Future research should focus on these novel approaches to achieve better clinical outcomes and improve the functional level and quality of life for individuals with schizophrenia.

Dynamic aberrances of substantia nigra-relevant coactivation patterns in first-episode treatment-naïve patients with schizophrenia

BACKGROUND

Although dopaminergic disturbances are well-known in schizophrenia, the understanding of dopamine-related brain dynamics remains limited. This study investigates the dynamic coactivation patterns (CAPs) associated with the substantia nigra (SN), a key dopaminergic nucleus, in first-episode treatment-naïve patients with schizophrenia (FES).

METHODS

Resting-state fMRI data were collected from 84 FES and 94 healthy controls (HCs). Frame-wise clustering was implemented to generate CAPs related to SN activation or deactivation. Connectome features of each CAP were derived using an edge-centric method. The occurrence for each CAP and the balance ratio for antagonistic CAPs were calculated and compared between two groups, and correlations between temporal dynamic metrics and symptom burdens were explored.

RESULTS

Functional reconfigurations in CAPs exhibited significant differences between the activation and deactivation states of SN. During SN activation, FES more frequently recruited a CAP characterized by activated default network, language network, control network, and the caudate, compared to HCs (F = 8.54, FDR-p = 0.030). Moreover, FES displayed a tilted balance towards a CAP featuring SN-coactivation with the control network, caudate, and thalamus, as opposed to its antagonistic CAP (F = 7.48, FDR-p = 0.030). During SN deactivation, FES exhibited increased recruitment of a CAP with activated visual and dorsal attention networks but decreased recruitment of its opposing CAP (F = 6.58, FDR-p = 0.034).

CONCLUSION

Our results suggest that neuroregulatory dysfunction in dopaminergic pathways involving SN potentially mediates aberrant time-varying functional reorganizations in schizophrenia. This finding enriches the dopamine hypothesis of schizophrenia from the perspective of brain dynamics.

Dysconnectivity of the Nucleus Accumbens and Amygdala in Youths with Thought Problems: A Dimensional Approach

Background: Youths with thought problems (TP) are at risk to develop psychosis and obsessive-compulsive disorder (OCD). Yet, the pathophysiological mechanisms underpinning TP are still unclear. Functional magnetic resonance imaging (fMRI) studies have shown that striatal and limbic alterations are associated with psychosis-like and obsessive-like symptoms in individuals at clinical risk for psychosis, schizophrenia, and OCD. More specifically, nucleus accumbens (NAcc) and amygdala are mainly involved in these associations. The current study aims to investigate the neural correlates of TP in youth populations using a dimensional approach and explore potential cognitive functions and neurotransmitters associated with it. Methods: Seed-to-voxels functional connectivity analyses using NAcc and amygdala as regions-of-interest were conducted with resting-state fMRI data obtained from 1360 young individuals, and potential confounders related to TP such as anxiety and cognitive functions were included as covariates in multiple regression analyses. Replicability was tested in using an adult cohort. In addition, functional decoding and neurochemical correlation analyses were performed to identify the associated cognitive functions and neurotransmitters. Results: The altered functional connectivities between the right NAcc and posterior parahippocampal gyrus, between the right amygdala and lateral prefrontal cortex, and between the left amygdala and the secondary visual area were the best predictors of TP in multiple regression model. These functional connections are mainly involved in social cognition and reward processing. Conclusions: The results show that alterations in the functional connectivity of the NAcc and the amygdala in neural pathways involved in social cognition and reward processing are associated with severity of TP in youths.

Striatum- and Cerebellum-Modulated Epileptic Networks Varying Across States with and without Interictal Epileptic Discharges

Idiopathic generalized epilepsy (IGE) is characterized by cryptogenic etiology and the striatum and cerebellum are recognized as modulators of epileptic network. We collected simultaneous electroencephalogram and functional magnetic resonance imaging data from 145 patients with IGE, 34 of whom recorded interictal epileptic discharges (IEDs) during scanning. In states without IEDs, hierarchical connectivity was performed to search core cortical regions which might be potentially modulated by striatum and cerebellum. Node-node and edge-edge moderation models were constructed to depict direct and indirect moderation effects in states with and without IEDs. Patients showed increased hierarchical connectivity with sensorimotor cortices (SMC) and decreased connectivity with regions in the default mode network (DMN). In the state without IEDs, striatum, cerebellum, and thalamus were linked to weaken the interactions of regions in the salience network (SN) with DMN and SMC. In periods with IEDs, overall increased moderation effects on the interaction between regions in SN and DMN, and between regions in DMN and SMC were observed. The thalamus and striatum were implicated in weakening interactions between regions in SN and SMC. The striatum and cerebellum moderated the cortical interaction among DMN, SN, and SMC in alliance with the thalamus, contributing to the dysfunction in states with and without IEDs in IGE. The current work revealed state-specific modulation effects of striatum and cerebellum on thalamocortical circuits and uncovered the potential core cortical targets which might contribute to develop new clinical neuromodulation techniques.

65 years of research on dopamine's role in classical fear conditioning and extinction: A systematic review

Dopamine, a catecholamine neurotransmitter, has historically been associated with the encoding of reward, whereas its role in aversion has received less attention. Here, we systematically gathered the vast evidence of the role of dopamine in the simplest forms of aversive learning: classical fear conditioning and extinction. In the past, crude methods were used to augment or inhibit dopamine to study its relationship with fear conditioning and extinction. More advanced techniques such as conditional genetic, chemogenic and optogenetic approaches now provide causal evidence for dopamine's role in these learning processes. Dopamine neurons encode conditioned stimuli during fear conditioning and extinction and convey the signal via activation of D1-4 receptor sites particularly in the amygdala, prefrontal cortex and striatum. The coordinated activation of dopamine receptors allows for the continuous formation, consolidation, retrieval and updating of fear and extinction memory in a dynamic and reciprocal manner. Based on the reviewed literature, we conclude that dopamine is crucial for the encoding of classical fear conditioning and extinction and contributes in a way that is comparable to its role in encoding reward.

Altered Perception of Environmental Volatility During Social Learning in Emerging Psychosis

Paranoid delusions or unfounded beliefs that others intend to deliberately cause harm are a frequent and burdensome symptom in early psychosis, but their emergence and consolidation still remains opaque. Recent theories suggest that overly precise prediction errors lead to an unstable model of the world providing a breeding ground for delusions. Here, we employ a Bayesian approach to test for such an unstable model of the world and investigate the computational mechanisms underlying emerging paranoia. We modelled behaviour of 18 first-episode psychosis patients (FEP), 19 individuals at clinical high risk for psychosis (CHR-P), and 19 healthy controls (HC) during an advice-taking task designed to probe learning about others' changing intentions. We formulated competing hypotheses comparing the standard Hierarchical Gaussian Filter (HGF), a Bayesian belief updating scheme, with a mean-reverting HGF to model an altered perception of volatility. There was a significant group-by-volatility interaction on advice-taking suggesting that CHR-P and FEP displayed reduced adaptability to environmental volatility. Model comparison favored the standard HGF in HC, but the mean-reverting HGF in CHR-P and FEP in line with perceiving increased volatility, although model attributions in CHR-P were heterogeneous. We observed correlations between perceiving increased volatility and positive symptoms generally as well as with frequency of paranoid delusions specifically. Our results suggest that FEP are characterised by a different computational mechanism - perceiving the environment as increasingly volatile - in line with Bayesian accounts of psychosis. This approach may prove useful to investigate heterogeneity in CHR-P and identify vulnerability for transition to psychosis.

Microglia at the Tripartite Synapse during Postnatal Development: Implications for Autism Spectrum Disorders and Schizophrenia

Synapses are the fundamental structures of neural circuits that control brain functions and behavioral and cognitive processes. Synapses undergo formation, maturation, and elimination mainly during postnatal development via a complex interplay with neighboring astrocytes and microglia that, by shaping neural connectivity, may have a crucial role in the strengthening and weakening of synaptic functions, that is, the functional plasticity of synapses. Indeed, an increasing number of studies have unveiled the roles of microglia and astrocytes in synapse formation, maturation, and elimination as well as in regulating synaptic function. Over the past 15 years, the mechanisms underlying the microglia- and astrocytes-dependent regulation of synaptic plasticity have been thoroughly studied, and researchers have reported that the disruption of these glial cells in early postnatal development may underlie the cause of synaptic dysfunction that leads to neurodevelopmental disorders such as autism spectrum disorder (ASD) and schizophrenia.

Emotional interference and attentional control in schizophrenia-spectrum disorders: The special case of neutral faces

BACKGROUND AND OBJECTIVES

Schizophrenia-spectrum disorders (SSD) are characterized by impaired emotion processing and attention. SSD patients are more sensitive to the presence of emotional distractors. But despite growing interest on the emotion-attention interplay, emotional interference in SSD is far from fully understood. Moreover, research to date has not established the link between emotional interference and attentional control in SSD. This study thus aimed to investigate the effects of facial expression and attentional control in SSD, by manipulating perceptual load.

METHODS

Twenty-two SSD patients and 22 healthy controls performed a target-letter discrimination task with task-irrelevant angry, happy, and neutral faces. Target-letter was presented among homogenous (low load) or heterogenous (high load) distractor-letters. Accuracy and RT were analysed using (generalized) linear mixed-effect models.

RESULTS

Accuracy was significantly lower in SSD patients than controls, regardless of perceptual load and facial expression. Concerning RT, SSD patients were significantly slower than controls in the presence of neutral faces, but only at high load. No group differences were observed for angry and happy faces.

LIMITATIONS

Heterogeneity of SSD, small sample size, lack of clinical control group, medication.

CONCLUSIONS

One possible explanation is that neutral faces captured exogenous attention to a greater extent in SSD, thus challenging attentional control in perceptually demanding conditions. This may reflect abnormal processing of neutral faces in SSD. If replicated, these findings will help to understand the interplay between exogenous attention, attentional control, and emotion processing in SSD, which may unravel the mechanism underlying socioemotional dysfunction in SSD.

Integrative Brain Network and Salience Models of Psychopathology and Cognitive Dysfunction in Schizophrenia

Brain network models of cognitive control are central to advancing our understanding of psychopathology and cognitive dysfunction in schizophrenia. This review examines the role of large-scale brain organization in schizophrenia, with a particular focus on a triple-network model of cognitive control and its role in aberrant salience processing. First, we provide an overview of the triple network involving the salience, frontoparietal, and default mode networks and highlight the central role of the insula-anchored salience network in the aberrant mapping of salient external and internal events in schizophrenia. We summarize the extensive evidence that has emerged from structural, neurochemical, and functional brain imaging studies for aberrancies in these networks and their dynamic temporal interactions in schizophrenia. Next, we consider the hypothesis that atypical striatal dopamine release results in misattribution of salience to irrelevant external stimuli and self-referential mental events. We propose an integrated triple-network salience-based model incorporating striatal dysfunction and sensitivity to perceptual and cognitive prediction errors in the insula node of the salience network and postulate that dysregulated dopamine modulation of salience network-centered processes contributes to the core clinical phenotype of schizophrenia. Thus, a powerful paradigm to characterize the neurobiology of schizophrenia emerges when we combine conceptual models of salience with large-scale cognitive control networks in a unified manner. We conclude by discussing potential therapeutic leads on restoring brain network dysfunction in schizophrenia.

Spurious Autobiographical Memory of Psychosis: A Mechanistic Hypothesis for the Resolution, Persistence, and Recurrence of Positive Symptoms in Psychotic Disorders

Psychotic disorders are complex disorders with multiple etiologies. While increased dopamine synthesis capacity has been proposed to underlie psychotic episodes, dopamine-independent processes are also involved (less responsive to dopamine receptor-blocking medications). The underlying mechanism(s) of the reduction in antipsychotic responsiveness over time, especially after repeated relapses, remain unclear. Despite the consistent evidence of dopamine overactivity and hippocampal volume loss in schizophrenia, few accounts have been provided based on the interactive effect of dopamine on hippocampal synapse plasticity mediating autobiographical memory processes. The present hypothesis builds upon previous works showing the potential effects of dopamine overactivity on hippocampal-mediated neuroplasticity underlying autobiographical memory, alongside known patterns of autobiographical memory dysfunction in psychosis. We propose that spurious autobiographical memory of psychosis (SAMP) produced during active psychosis may be a key mechanism mediating relapses and treatment non-responsiveness. In a hyperdopaminergic state, SAMP is expected to be generated at an increased rate during active psychosis. Similar to other memories, it will undergo assimilation, accommodation, and extinction processes. However, if SAMP fails to integrate with existing memory, a discontinuity in autobiographical memory may result. Inadequate exposure to normalizing experiences and hyposalience due to overmedication or negative symptoms may also impede the resolution of SAMP. Residual SAMP is hypothesized to increase the propensity for relapse and treatment non-responsiveness. Based on recent findings on the role of dopamine in facilitating hippocampal synapse plasticity and autobiographical memory formation, the SAMP hypothesis is consistent with clinical observations of DUP effects, including the repetition of contents in psychotic relapses as well as the emergence of treatment non-responsiveness after repeated relapses. Clinical implications of the hypothesis highlight the importance of minimizing active psychosis, integrating psychosis memory, avoiding over-medication, and fostering normalizing experiences.

Progressive trajectories of schizophrenia across symptoms, genes, and the brain

BACKGROUND

Schizophrenia is characterized by complex psychiatric symptoms and unclear pathological mechanisms. Most previous studies have focused on the morphological changes that occur over the development of the disease; however, the corresponding functional trajectories remain unclear. In the present study, we aimed to explore the progressive trajectories of patterns of dysfunction after diagnosis.

METHODS

Eighty-six patients with schizophrenia and 120 healthy controls were recruited as the discovery dataset. Based on multiple functional indicators of resting-state brain functional magnetic resonance imaging, we conducted a duration-sliding dynamic analysis framework to investigate trajectories in association with disease progression. Neuroimaging findings were associated with clinical symptoms and gene expression data from the Allen Human Brain Atlas database. A replication cohort of patients with schizophrenia from the University of California, Los Angeles, was used as the replication dataset for the validation analysis.

RESULTS

Five stage-specific phenotypes were identified. A symptom trajectory was characterized by positive-dominated, negative ascendant, negative-dominated, positive ascendant, and negative surpassed stages. Dysfunctional trajectories from primary and subcortical regions to higher-order cortices were recognized; these are associated with abnormal external sensory gating and a disrupted internal excitation-inhibition equilibrium. From stage 1 to stage 5, the importance of neuroimaging features associated with behaviors gradually shifted from primary to higher-order cortices and subcortical regions. Genetic enrichment analysis identified that neurodevelopmental and neurodegenerative factors may be relevant as schizophrenia progresses and highlighted multiple synaptic systems.

CONCLUSIONS

Our convergent results indicate that progressive symptoms and functional neuroimaging phenotypes are associated with genetic factors in schizophrenia. Furthermore, the identification of functional trajectories complements previous findings of structural abnormalities and provides potential targets for drug and non-drug interventions in different stages of schizophrenia.

Mass Spectrometry based identification of site-specific proteomic alterations and potential pathways underlying the pathophysiology of schizophrenia

BACKGROUND

Schizophrenia (SZ) is a complex multifactorial disorder that affects 1% of the population worldwide with no available effective treatment. Although proteomic alterations are reported in SZ however proteomic expression aberrations among different brain regions are not fully determined. Therefore, the present study aimed spatial differential protein expression profiling of three distinct regions of SZ brain and identification of associated affected biological pathways in SZ progression.

METHODS AND RESULTS

Comparative protein expression profiling of three distinct autopsied human brain regions (i.e., substantia nigra, hippocampus and prefrontal cortex) of SZ was performed with respective healthy controls. Using two-dimensional electrophoresis (2DE)-based nano liquid chromatography tandem mass spectrometry (Nano-LC MS /MS) analysis, 1443 proteins were identified out of which 58 connote to be significantly dysregulated, representing 26 of substantia nigra,14 of hippocampus and 18 of prefrontal cortex. The 58 differentially expressed proteins were further analyzed using Ingenuity pathway analysis (IPA). The IPA analysis provided protein-protein interaction networks of several proteins including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kb), extracellular signal regulated kinases 1/2 (ERK1/2), alpha serine / Threonine-protein kinase (AKT1), cellular tumor antigen p53 (TP53) and amyloid precursor protein (APP), holding prime positions in networks and interacts with most of the identified proteins and their closely interacting partners.

CONCLUSION

These findings provide conceptual insights of novel SZ related pathways and the cross talk of co and contra regulated proteins. This spatial proteomic analysis will further broaden the conceptual framework for schizophrenia research in future.

Does partial blockade of dopamine D2 receptors with Amisulpride cause anhedonia? An experimental study in healthy volunteers

BACKGROUND

Anhedonia is a frequent cause of functional im^pairment in psychosis. Although it is plausible that medication-induced D2 receptor blockade could diminish hedonic responding, there is little experimental research testing this hypothesis in humans.

METHODS

To inspect possible effects of partial D2 blockade on hedonic experiences, we administered 300 mg of Amisulpride or placebo to 85 participants in a randomized, double-blind, placebo-controlled trial. Participants were then subjected to an emotional evocation task utilizing standardized pictorial pleasant, neutral, and unpleasant stimuli.

RESULTS

We observed lower positivity ratings in the Amisulpride group compared to placebo across all stimulus categories (p = .026, f = 0.25) and no group differences in negativity or arousal ratings. The Amisulpride group also showed lower electrodermal responses across all stimulus categories compared to placebo (p = .017, f = 0.27). The electrodermal response was especially diminished for pleasant stimuli.

CONCLUSION

We interpret our findings as evidence that D2 blockade via Amisulpride can reduce at-the-moment hedonic responsivity in healthy volunteers. If these results can be confirmed in drug-naïve clinical samples, this would indicate that antipsychotic medication contributes to clinical anhedonia, probably via antagonistic effects at the dopamine D2 receptor.

Unraveling the mysteries of dendritic spine dynamics: Five key principles shaping memory and cognition

Recent research extends our understanding of brain processes beyond just action potentials and chemical transmissions within neural circuits, emphasizing the mechanical forces generated by excitatory synapses on dendritic spines to modulate presynaptic function. From in vivo and in vitro studies, we outline five central principles of synaptic mechanics in brain function: P1: Stability - Underpinning the integral relationship between the structure and function of the spine synapses. P2: Extrinsic dynamics - Highlighting synapse-selective structural plasticity which plays a crucial role in Hebbian associative learning, distinct from pathway-selective long-term potentiation (LTP) and depression (LTD). P3: Neuromodulation - Analyzing the role of G-protein-coupled receptors, particularly dopamine receptors, in time-sensitive modulation of associative learning frameworks such as Pavlovian classical conditioning and Thorndike's reinforcement learning (RL). P4: Instability - Addressing the intrinsic dynamics crucial to memory management during continual learning, spotlighting their role in "spine dysgenesis" associated with mental disorders. P5: Mechanics - Exploring how synaptic mechanics influence both sides of synapses to establish structural traces of short- and long-term memory, thereby aiding the integration of mental functions. We also delve into the historical background and foresee impending challenges.

Glutamatergic dysfunction leads to a hyper-dopaminergic phenotype through deficits in short-term habituation: a mechanism for aberrant salience

Psychosis in disorders like schizophrenia is commonly associated with aberrant salience and elevated striatal dopamine. However, the underlying cause(s) of this hyper-dopaminergic state remain elusive. Various lines of evidence point to glutamatergic dysfunction and impairments in synaptic plasticity in the etiology of schizophrenia, including deficits associated with the GluA1 AMPAR subunit. GluA1 knockout (Gria1^-/-) mice provide a model of impaired synaptic plasticity in schizophrenia and exhibit a selective deficit in a form of short-term memory which underlies short-term habituation. As such, these mice are unable to reduce attention to recently presented stimuli. In this study we used fast-scan cyclic voltammetry to measure phasic dopamine responses in the nucleus accumbens of Gria1^-/- mice to determine whether this behavioral phenotype might be a key driver of a hyper-dopaminergic state. There was no effect of GluA1 deletion on electrically-evoked dopamine responses in anaesthetized mice, demonstrating normal endogenous release properties of dopamine neurons in Gria1^-/- mice. Furthermore, dopamine signals were initially similar in Gria1^-/- mice compared to controls in response to both sucrose rewards and neutral light stimuli. They were also equally sensitive to changes in the magnitude of delivered rewards. In contrast, however, these stimulus-evoked dopamine signals failed to habituate with repeated presentations in Gria1^-/- mice, resulting in a task-relevant, hyper-dopaminergic phenotype. Thus, here we show that GluA1 dysfunction, resulting in impaired short-term habituation, is a key driver of enhanced striatal dopamine responses, which may be an important contributor to aberrant salience and psychosis in psychiatric disorders like schizophrenia.

Belief Updating in Subclinical and Clinical Delusions

Background and Hypothesis

Current frameworks propose that delusions result from aberrant belief updating due to altered prediction error (PE) signaling and misestimation of environmental volatility. We aimed to investigate whether behavioral and neural signatures of belief updating are specifically related to the presence of delusions or generally associated with manifest schizophrenia.

Methods

Our cross-sectional design includes human participants (n[female/male] = 66[25/41]), stratified into four groups: healthy participants with minimal (n = 22) or strong delusional-like ideation (n = 18), and participants with diagnosed schizophrenia with minimal (n = 13) or strong delusions (n = 13), resulting in a 2 × 2 design, which allows to test for the effects of delusion and diagnosis. Participants performed a reversal learning task with stable and volatile task contingencies during fMRI scanning. We formalized learning with a hierarchical Gaussian filter model and conducted model-based fMRI analysis regarding beliefs of outcome uncertainty and volatility, precision-weighted PEs of the outcome- and the volatility-belief.

Results

Patients with schizophrenia as compared to healthy controls showed lower accuracy and heightened choice switching, while delusional ideation did not affect these measures. Participants with delusions showed increased precision-weighted PE-related neural activation in fronto-striatal regions. People with diagnosed schizophrenia overestimated environmental volatility and showed an attenuated neural representation of volatility in the anterior insula, medial frontal and angular gyrus.

Conclusions

Delusional beliefs are associated with altered striatal PE-signals. Juxtaposing, the potentially unsettling belief that the environment is constantly changing and weaker neural encoding of this subjective volatility seems to be associated with manifest schizophrenia, but not with the presence of delusional ideation.

Magnocellular and parvocellular contributions to brain network dysfunction during learning and memory: Implications for schizophrenia

Memory deficits are core features of schizophrenia, and a central aim in biological psychiatry is to identify the etiology of these deficits. Scrutiny is naturally focused on the dorsolateral prefrontal cortex and the hippocampal cortices, given these structures' roles in memory and learning. The fronto-hippocampal framework is valuable but restrictive. Network-based underpinnings of learning and memory are substantially diverse and include interactions between hetero-modal and early sensory networks. Thus, a loss of fidelity in sensory information may impact memorial and cognitive processing in higher-order brain sub-networks, becoming a sensory source for learning and memory deficits. In this overview, we suggest that impairments in magno- and parvo-cellular visual pathways result in degraded inputs to core learning and memory networks. The ascending cascade of aberrant neural events significantly contributes to learning and memory deficits in schizophrenia. We outline the network bases of these effects, and suggest that any network perspectives of dysfunction in schizophrenia must assess the impact of impaired perceptual contributions. Finally, we speculate on how this framework enriches the space of biomarkers and expands intervention strategies to ameliorate this prototypical disconnection syndrome.

The effects of AUT00206, a novel Kv3.1/3.2 potassium channel modulator, on task-based reward system activation: a test of mechanism in schizophrenia

The pathophysiology of schizophrenia involves abnormal reward processing, thought to be due to disrupted striatal and dopaminergic function. Consistent with this hypothesis, functional magnetic resonance imaging (fMRI) studies using the monetary incentive delay (MID) task report hypoactivation in the striatum during reward anticipation in schizophrenia. Dopamine neuron activity is modulated by striatal GABAergic interneurons. GABAergic interneuron firing rates, in turn, are related to conductances in voltage-gated potassium 3.1 (Kv3.1) and 3.2 (Kv3.2) channels, suggesting that targeting Kv3.1/3.2 could augment striatal function during reward processing. Here, we studied the effect of a novel potassium Kv3.1/3.2 channel modulator, AUT00206, on striatal activation in patients with schizophrenia, using the MID task. Each participant completed the MID during fMRI scanning on two occasions: once at baseline, and again following either 4 weeks of AUT00206 or placebo treatment. We found a significant inverse relationship at baseline between symptom severity and reward anticipation-related neural activation in the right associative striatum (r = -0.461, p = 0.035). Following treatment with AUT00206, there was a significant increase in reward anticipation-related activation in the left associative striatum (t₍₁₃₎ = 4.23, peak-level p(FWE) < 0.05)), but no significant effect in the ventral striatum. This provides preliminary evidence that the Kv3.1/3.2 potassium channel modulator, AUT00206, may address reward-related striatal abnormalities in schizophrenia.

Validation of the aberrant salience inventory in a general and clinical Spanish population

BACKGROUND

The concept of aberrant salience is related to the onset of psychosis. Its study is important for early identification and possible intervention in processes activating later positive symptoms.

OBJECTIVES

This study validated the Spanish Aberrant Salience Inventory (ASI) for adult and clinical populations.

METHODS

The sample consisted of 6178 participants, of whom 4523 were adolescents, 1292 were general population adults and 363 were patients with a psychopathology.

RESULTS

The evidence provided validates the instrument's structure. Invariance of measurement suggests that both men and women, patients and nonclinical population (adults and adolescents) interpreted the items on the ASI similarly. The distribution of scores by age also suggests stabilization of the trend at about 19 years of age, showing a developmental change in motivational response. The hypothesis that patients, and in particular, those diagnosed with schizophrenia and other psychotic disorders and bipolar disorders would have the highest average scores in aberrant salience was met.

CONCLUSIONS

This is a valuable instrument for evaluating a complex process related to abnormal motivation in the development of schizophrenia.

The Interrelation between Interleukin-2 and Schizophrenia

Interleukin-2 (IL-2) is a growth factor that regulates T-cell autocrine secretion and has long been considered to be closely related to immune response. With the advance in neuroinflammation theory and immunology research on schizophrenia, it is interesting and meaningful to discuss the possible role of IL-2 in schizophrenia. Here, we reviewed a series of studies published from the 1990s and found that IL-2 was closely associated with schizophrenia. For example, IL-2 is responsible for mediating toxic reactions, which are the causes of schizophrenia symptoms in patients, and such symptoms resolve after discontinuation of the drug. In addition, we focused on the changes of IL-2 in the onset, progression and treatment of schizophrenia and the possible mechanisms by which IL-2 affects schizophrenia. Our review suggests that IL-2 is associated with schizophrenia and plays a role in its pathogenesis, and progression IL-2 and sIL-2R could serve as potential biomarkers of schizophrenia.

Dopamine activity on the perceptual salience for recognition memory

To survive, animals must recognize relevant stimuli and distinguish them from inconspicuous information. Usually, the properties of the stimuli, such as intensity, duration, frequency, and novelty, among others, determine the salience of the stimulus. However, previously learned experiences also facilitate the perception and processing of information to establish their salience. Here, we propose “perceptual salience” to define how memory mediates the integration of inconspicuous stimuli into a relevant memory trace without apparently altering the recognition of the physical attributes or valence, enabling the detection of stimuli changes in future encounters. The sense of familiarity is essential for successful recognition memory; in general, familiarization allows the transition of labeling a stimulus from the novel (salient) to the familiar (non-salient). The novel object recognition (NOR) and object location recognition (OLRM) memory paradigms represent experimental models of recognition memory that allow us to study the neurobiological mechanisms involved in episodic memory. The catecholaminergic system has been of vital interest due to its role in several aspects of recognition memory. This review will discuss the evidence that indicates changes in dopaminergic activity during exposure to novel objects or places, promoting the consolidation and persistence of memory. We will discuss the relationship between dopaminergic activity and perceptual salience of stimuli enabling learning and consolidation processes necessary for the novel-familiar transition. Finally, we will describe the effect of dopaminergic deregulation observed in some pathologies and its impact on recognition memory.

The lived experience of psychosis: a bottom-up review co-written by experts by experience and academics

Psychosis is the most ineffable experience of mental disorder. We provide here the first co-written bottom-up review of the lived experience of psychosis, whereby experts by experience primarily selected the subjective themes, that were subsequently enriched by phenomenologically-informed perspectives. First-person accounts within and outside the medical field were screened and discussed in collaborative workshops involving numerous individuals with lived experience of psychosis as well as family members and carers, representing a global network of organizations. The material was complemented by semantic analyses and shared across all collaborators in a cloud-based system. The early phases of psychosis (i.e., premorbid and prodromal stages) were found to be characterized by core existential themes including loss of common sense, perplexity and lack of immersion in the world with compromised vital contact with reality, heightened salience and a feeling that something important is about to happen, perturbation of the sense of self, and need to hide the tumultuous inner experiences. The first episode stage was found to be denoted by some transitory relief associated with the onset of delusions, intense self-referentiality and permeated self-world boundaries, tumultuous internal noise, and dissolution of the sense of self with social withdrawal. Core lived experiences of the later stages (i.e., relapsing and chronic) involved grieving personal losses, feeling split, and struggling to accept the constant inner chaos, the new self, the diagnosis and an uncertain future. The experience of receiving psychiatric treatments, such as inpatient and outpatient care, social interventions, psychological treatments and medications, included both positive and negative aspects, and was determined by the hope of achieving recovery, understood as an enduring journey of reconstructing the sense of personhood and re-establishing the lost bonds with others towards meaningful goals. These findings can inform clinical practice, research and education. Psychosis is one of the most painful and upsetting existential experiences, so dizzyingly alien to our usual patterns of life and so unspeakably enigmatic and human.

Affective Dysregulation Precedes Emergence of Psychosis-Like Experiences in a Community Sample of Young Adults

Affective dysregulation (AD) among persons with schizophrenia spectrum disorders, involving the tendency to exhibit sensitivity to minor stress and negative affective states, is an important diagnostic feature and relates to poorer functional and clinical outcomes. Studies of persons with elevated risk for psychosis demonstrate similar AD to those with schizophrenia, and literature suggest a potential influence of AD in the transition from psychosis-like symptoms (PLEs) to disorder. Cross-sectional investigations to date have supported the link between AD and psychosis, and longitudinal studies have mostly yielded mixed findings without demonstration of potential causal relationships between AD and psychosis. This study examined the concurrent and predictive relationships between AD and PLE in a community sample of youth (n = 630) with attention to distinct facets of AD as a latent construct, including low resiliency, low reactive control, and negative emotionality, using structural equation to estimate a longitudinal cross-lagged and autoregressive model across 3 study waves from 15 to 24 years of age. As hypothesized, AD in the mid-teen years predicted subsequent PLE 3 years later. In addition, we found that increasing PLE in the end of the teen years related to a subsequent increase in AD in the early 20s. A cross-sectional relationship between AD and PLE in the mid-teen years was also supported. Findings overall describe important relationships between AD and PLE that appear to vary with developmental stage, implicating various factors to inform approaches for identifying youth who may be at risk for subsequent PLE or other mental health conditions.

Role of Oxytocin in Different Neuropsychiatric, Neurodegenerative, and Neurodevelopmental Disorders

Oxytocin has recently gained significant attention because of its role in the pathophysiology and management of dominant neuropsychiatric disorders. Oxytocin, a peptide hormone synthesized in the hypothalamus, is released into different brain regions, acting as a neurotransmitter. Receptors for oxytocin are present in many areas of the brain, including the hypothalamus, amygdala, and nucleus accumbens, which have been involved in the pathophysiology of depression, anxiety, schizophrenia, autism, Alzheimer's disease, Parkinson's disease, and attention deficit hyperactivity disorder. Animal studies have spotlighted the role of oxytocin in social, behavioral, pair bonding, and mother-infant bonding. Furthermore, oxytocin protects fetal neurons against injury during childbirth and affects various behaviors, assuming its possible neuroprotective characteristics. In this review, we discuss some of the concepts and mechanisms related to the role of oxytocin in the pathophysiology and management of some neuropsychiatric, neurodegenerative, and neurodevelopmental disorders.

Neural Circuitry of Salience and Reward Processing in Psychosis

The processing of salient and rewarding stimuli is integral to engaging our attention, stimulating anticipation for future events, and driving goal-directed behaviors. Widespread impairments in these processes are observed in psychosis, which may be associated with worse functional outcomes or mechanistically linked to the development of symptoms. Here, we summarize the current knowledge of behavioral and functional neuroimaging in salience, prediction error, and reward. Although each is a specific process, they are situated in multiple feedback and feedforward systems integral to decision making and cognition more generally. We argue that the origin of salience and reward processing dysfunctions may be centered in the subcortex during the earliest stages of psychosis, with cortical abnormalities being initially more spared but becoming more prominent in established psychotic illness/schizophrenia. The neural circuits underpinning salience and reward processing may provide targets for delaying or preventing progressive behavioral and neurobiological decline.

The role of aberrant salience in the association between cannabis use frequency and psychotic experiences among racial and ethnic minoritized youth

Prior studies have shown cannabis use is correlated with psychotic symptoms, but few have explored potential underlying mechanisms. The present study examined whether aberrant salience explains the association between cannabis use frequency and psychotic experiences (PE) while accounting for the mediating role of anxiety in this association. A US urban undergraduate sample of 816 racial and ethnic minorities contributed data used in linear regression models to determine associations between recent (3 months) cannabis use frequency, aberrant salience, anxiety, positive subscale Prodromal Questionnaire (PQ) items, and distressing positive PQ items. Results from hierarchical linear regression and mediation models using Hayes PROCESS application indicated the association between cannabis use frequency and PE was significantly explained by higher aberrant salience and anxiety. Furthermore, anxiety's indirect association with cannabis use frequency and PE significantly occurred through aberrant salience's indirect association with cannabis use frequency and PE (i.e., serial mediation). A similar pattern emerged for distressing PE. We also found earlier age of cannabis use onset (age 12-14) was associated with a higher number of PE and distressing PE and that this was partially explained by higher aberrant salience. Anxiety's indirect association between earlier age of onset and PE/distressing PE only occurred through aberrant salience (i.e., serial mediation). Aberrant salience may be the part of psychosis proneness most directly connected to why earlier initiation of cannabis use is a risk factor for psychotic disorders. This should be explored further in future longitudinal work with clinical high-risk populations and among minoritized youth.

Lipopeptide Pepducins as Therapeutic Agents

Pepducins are lipidated peptides that target the intracellular loops of G protein-coupled receptors (GPCRs) in order to modulate transmembrane signaling to internally located effectors. With a wide array of potential activities ranging from partial, biased, or full agonism to antagonism, pepducins represent a versatile class of compounds that can be used to potentially treat diverse human diseases or be employed as novel tools to probe complex mechanisms of receptor activation and signaling in cells and in animals. Here, we describe a number of different pepducins including an advanced compound, PZ-128, that has successfully progressed through phase 2 clinical trials in cardiac patients demonstrating safety and efficacy in suppressing myonecrosis and arterial thrombosis.

Aberrant Learned Irrelevance in Patients with First-Episode Schizophrenia-Spectrum Disorder

Emerging evidence has indicated disrupted learned irrelevance (LIrr), a form of selective attention deficit that may contribute to psychotic symptom formation, in schizophrenia. However, previous research mostly focused on chronic patients. There is a paucity of studies on LIrr in first-episode schizophrenia-spectrum disorder (i.e., schizophrenia and schizophreniform disorder; FES), which were limited by small sample size and have produced mixed results. The current study examined a LIrr effect and its relationship with positive symptom severity in 40 briefly-medicated FES patients and 42 demographically-matched healthy controls using a well-validated computerized LIrr paradigm which has been applied in chronic schizophrenia sample. Positive symptoms were assessed by Positive and Negative Syndrome Scale (PANSS) and Psychotic Symptom Rating Scales (PSYRATS). Our results showed that controls demonstrated intact LIrr, with significantly faster learning about previously predictive (relevant) than previously non-predictive (irrelevant) cues. Lack of such normal attention bias towards predictive over non-predictive cues was observed in FES patients, indicating their failure to distinguish between relevant and irrelevant stimuli. Nonetheless, we failed to reveal any significant correlations between learning scores, in particular learning scores for non-predictive cues, and positive symptom measures in FES patients. Learning scores were also not associated with other symptom dimensions, cognitive functions and antipsychotic dose. In conclusion, our findings indicate aberrant LIrr with impaired allocation of attention to relevant versus irrelevant stimuli in briefly-medicated FES patients. Further prospective research is warranted to clarify the longitudinal trajectory of such selective attention deficit and its association with positive symptoms and treatment response in the early course of illness.

Neural Correlates of Aberrant Salience and Source Monitoring in Schizophrenia and At-Risk Mental States-A Systematic Review of fMRI Studies

Cognitive biases are an important factor contributing to the development and symptom severity of psychosis. Despite the fact that various cognitive biases are contributing to psychosis, they are rarely investigated together. In the current systematic review, we aimed at investigating specific and shared functional neural correlates of two important cognitive biases: aberrant salience and source monitoring. We conducted a systematic search of fMRI studies of said cognitive biases. Eight studies on aberrant salience and eleven studies on source monitoring were included in the review. We critically discussed behavioural and neuroimaging findings concerning cognitive biases. Various brain regions are associated with aberrant salience and source monitoring in individuals with schizophrenia and the risk of psychosis. The ventral striatum and insula contribute to aberrant salience. The medial prefrontal cortex, superior and middle temporal gyrus contribute to source monitoring. The anterior cingulate cortex and hippocampus contribute to both cognitive biases, constituting a neural overlap. Our review indicates that aberrant salience and source monitoring may share neural mechanisms, suggesting their joint role in producing disrupted external attributions of perceptual and cognitive experiences, thus elucidating their role in positive symptoms of psychosis. Account bridging mechanisms of these two biases is discussed. Further studies are warranted.

Effective Connectivity of the Hippocampus Can Differentiate Patients with Schizophrenia from Healthy Controls: A Spectral DCM Approach

We applied spectral dynamic causal modelling (Friston et al. in Neuroimage 94:396–407. 10.1016/j.neuroimage.2013.12.009, 2014) to analyze the effective connectivity differences between the nodes of three resting state networks (i.e. default mode network, salience network and dorsal attention network) in a dataset of 31 male healthy controls (HC) and 25 male patients with a diagnosis of schizophrenia (SZ). Patients showed increased directed connectivity from the left hippocampus (LHC) to the: dorsal anterior cingulate cortex (DACC), right anterior insula (RAI), left frontal eye fields and the bilateral inferior parietal sulcus (LIPS & RIPS), as well as increased connectivity from the right hippocampus (RHC) to the: bilateral anterior insula (LAI & RAI), right frontal eye fields and RIPS. In SZ, negative symptoms predicted the connectivity strengths from the LHC to: the DACC, the left inferior parietal sulcus (LIPAR) and the RHC, while positive symptoms predicted the connectivity strengths from the LHC to the LIPAR and from the RHC to the LHC. These results reinforce the crucial role of hippocampus dysconnectivity in SZ pathology and its potential as a biomarker of disease severity.

Insula to mPFC reciprocal connectivity differentially underlies novel taste neophobic response and learning in mice

To survive in an ever-changing environment, animals must detect and learn salient information. The anterior insular cortex (aIC) and medial prefrontal cortex (mPFC) are heavily implicated in salience and novelty processing, and specifically, the processing of taste sensory information. Here, we examined the role of aIC-mPFC reciprocal connectivity in novel taste neophobia and memory formation, in mice. Using pERK and neuronal intrinsic properties as markers for neuronal activation, and retrograde AAV (rAAV) constructs for connectivity, we demonstrate a correlation between aIC-mPFC activity and novel taste experience. Furthermore, by expressing inhibitory chemogenetic receptors in these projections, we show that aIC-to-mPFC activity is necessary for both taste neophobia and its attenuation. However, activity within mPFC-to-aIC projections is essential only for the neophobic reaction but not for the learning process. These results provide an insight into the cortical circuitry needed to detect, react to- and learn salient stimuli, a process critically involved in psychiatric disorders.

Actualities in immunological markers and electrochemical sensors for determination of dopamine and its metabolites in psychotic disorders (Review)

Psychotic disorders represent a serious health concern. At this moment, anamnestic data, international criteria for diagnosis/classification from the Diagnostic and Statistical Manual of Mental Disorders-5 and the International Classification of Diseases-10 and diagnostic scales are used to establish a diagnosis. The most commonly used biomarkers in psychotic illnesses are those regarding the neuroimmune system, metabolic abnormalities, neurotrophins and neurotransmitter systems and proteomics. A current issue faced by clinicians is the lack of biomarkers to help develop a more accurate diagnosis, with the possibility of initiating the most effective treatment. The detection of biological markers for psychosis has the potential to contribute to improvements in its diagnosis, prognosis and treatment effectiveness. The mixture of multiple biomarkers may improve the ability to differentiate and classify these patients. In this sense, the aim of this study was to analyze the literature concerning the potential biomarkers that could be used in medical practice and to review the newest developments in electrochemical sensors used for dopamine detection, one of the most important exploited biomarkers.

Reduced resting state functional connectivity in the hippocampus-midbrain-striatum network of schizophrenia patients

Contemporary preclinical models suggest that abnormal functioning of a brain network consisting of the hippocampus, midbrain and striatum plays a critical role in the pathophysiology of schizophrenia. Previous neuroimaging studies examined individual aspects of this model in schizophrenia patients and individuals at clinical high risk for psychosis. However, this exact preclinical brain network has not been translated to human neuroimaging studies with schizophrenia patients and therefore it is currently unknown how functioning of this network is altered in patients. Here we investigated resting state functional connectivity in the hippocampus-midbrain-striatum network of schizophrenia patients, using functional Magnetic Resonance Imaging. Based on preclinical models, a network of functionally validated brain regions comprising the anterior subiculum (SUB), limbic striatum (LS), ventral tegmental area (VTA) and associative striatum (AS) was examined in 47 schizophrenia patients and 51 healthy controls. Schizophrenia patients demonstrated significantly lower functional connectivity in this hippocampus-midbrain-striatum network compared with healthy controls (p = 0.036). Particular reductions in connectivity were found between the SUB and LS (0.002 ± 0.315 and 0.116 ± 0.224, p = 0.040) and between the VTA and AS (0.230 ± 0.268 and 0.356 ± 0.285, p = 0.026). In patients, functional connectivity was not significantly associated with positive, negative or general symptom scores. Reduced connectivity is consistent with the concept of functional brain dysconnectivity as a key feature of the disorder. Our results support the notion that functioning of the hippocampus-midbrain-striatum network is significantly altered in the pathophysiology of schizophrenia.

Spine dynamics in the brain, mental disorders and artificial neural networks

In the brain, most synapses are formed on minute protrusions known as dendritic spines. Unlike their artificial intelligence counterparts, spines are not merely tuneable memory elements: they also embody algorithms that implement the brain's ability to learn from experience and cope with new challenges. Importantly, they exhibit structural dynamics that depend on activity, excitatory input and inhibitory input (synaptic plasticity or 'extrinsic' dynamics) and dynamics independent of activity ('intrinsic' dynamics), both of which are subject to neuromodulatory influences and reinforcers such as dopamine. Here we succinctly review extrinsic and intrinsic dynamics, compare these with parallels in machine learning where they exist, describe the importance of intrinsic dynamics for memory management and adaptation, and speculate on how disruption of extrinsic and intrinsic dynamics may give rise to mental disorders. Throughout, we also highlight algorithmic features of spine dynamics that may be relevant to future artificial intelligence developments.

Understanding urbanicity: how interdisciplinary methods help to unravel the effects of the city on mental health

Twenty-first century urbanization poses increasing challenges for mental health. Epidemiological studies have shown that mental health problems often accumulate in urban areas, compared to rural areas, and suggested possible underlying causes associated with the social and physical urban environments. Emerging work indicates complex urban effects that depend on many individual and contextual factors at the neighbourhood and country level and novel experimental work is starting to dissect potential underlying mechanisms. This review summarizes findings from epidemiology and population-based studies, neuroscience, experimental and experience-based research and illustrates how a combined approach can move the field towards an increased understanding of the urbanicity-mental health nexus.

The Interplay Between Postsynaptic Striatal D2/3 Receptor Availability, Adversity Exposure and Odd Beliefs: A [11C]-Raclopride PET Study

BACKGROUND

Between unaffected mental health and diagnosable psychiatric disorders, there is a vast continuum of functioning. The hypothesized link between striatal dopamine signaling and psychosis has guided a prolific body of research. However, it has been understudied in the context of multiple interacting factors, subclinical phenotypes, and pre-postsynaptic dynamics.

METHOD

This work investigated psychotic-like experiences and D2/3 dopamine postsynaptic receptor availability in the dorsal striatum, quantified by in vivo [11C]-raclopride positron emission tomography, in a sample of 24 healthy male individuals. Additional mediation and moderation effects with childhood trauma and key dopamine-regulating genes were examined.

RESULTS

An inverse relationship between nondisplaceable binding potential and subclinical symptoms was identified. D2/3 receptor availability in the left putamen fully mediated the association between traumatic childhood experiences and odd beliefs, that is, inclinations to see meaning in randomness and unfounded interpretations. Moreover, the effect of early adversity was moderated by a DRD2 functional variant (rs1076560). The results link environmental and neurobiological influences in the striatum to the origination of psychosis spectrum symptomology, consistent with the social defeat and diathesis-stress models.

CONCLUSIONS

Adversity exposure may affect the dopamine system as in association with biases in probabilistic reasoning, attributional style, and salience processing. The inverse relationship between D2/3 availability and symptomology may be explained by endogenous dopamine occupying the receptor, postsynaptic compensatory mechanisms, and/or altered receptor sensitivity. This may also reflect a cognitively stabilizing mechanism in non-help-seeking individuals. Future research should comprehensively characterize molecular parameters of dopamine neurotransmission along the psychosis spectrum and according to subtype profiling.

Dopamine: The Neuromodulator of Long-Term Synaptic Plasticity, Reward and Movement Control

Dopamine (DA) is a key neurotransmitter involved in multiple physiological functions including motor control, modulation of affective and emotional states, reward mechanisms, reinforcement of behavior, and selected higher cognitive functions. Dysfunction in dopaminergic transmission is recognized as a core alteration in several devastating neurological and psychiatric disorders, including Parkinson's disease (PD), schizophrenia, bipolar disorder, attention deficit hyperactivity disorder (ADHD) and addiction. Here we will discuss the current insights on the role of DA in motor control and reward learning mechanisms and its involvement in the modulation of synaptic dynamics through different pathways. In particular, we will consider the role of DA as neuromodulator of two forms of synaptic plasticity, known as long-term potentiation (LTP) and long-term depression (LTD) in several cortical and subcortical areas. Finally, we will delineate how the effect of DA on dendritic spines places this molecule at the interface between the motor and the cognitive systems. Specifically, we will be focusing on PD, vascular dementia, and schizophrenia.

Distracting stimuli evoke ventral tegmental area responses in rats during ongoing saccharin consumption

Disruptions in attention, salience and increased distractibility are implicated in multiple psychiatric conditions. The ventral tegmental area (VTA) is a potential site for converging information about external stimuli and internal states to be integrated and guide adaptive behaviours. Given the dual role of dopamine signals in both driving ongoing behaviours (e.g., feeding) and monitoring salient environmental stimuli, understanding the interaction between these functions is crucial. Here, we investigate VTA neuronal activity during distraction from ongoing feeding. We developed a task to assess distraction exploiting self-paced licking in rats. Rats trained to lick for saccharin were given a distraction test, in which three consecutive licks within 1 s triggered a random distractor (e.g. light and tone stimulus). On each trial they were quantified as distracted or not based on the length of their pauses in licking behaviour. We expressed GCaMP6s in VTA neurons and used fibre photometry to record calcium fluctuations during this task as a proxy for neuronal activity. Distractor stimuli caused rats to interrupt their consumption of saccharin, a behavioural effect which quickly habituated with repeat testing. VTA neural activity showed consistent increases to distractor presentations and, furthermore, these responses were greater on distracted trials compared to non-distracted trials. Interestingly, neural responses show a slower habituation than behaviour with consistent VTA responses seen to distractors even after they are no longer distracting. These data highlight the complex role of the VTA in maintaining ongoing appetitive and consummatory behaviours while also monitoring the environment for salient stimuli.

Tonic GABAergic inhibition, via GABAA receptors containing αβƐ subunits, regulates excitability of ventral tegmental area dopamine neurons

The activity of midbrain dopamine neurons is strongly regulated by fast synaptic inhibitory γ‐Aminobutyric acid (GABA)ergic inputs. There is growing evidence in other brain regions that low concentrations of ambient GABA can persistently activate certain subtypes of GABA_A receptor to generate a tonic current. However, evidence for a tonic GABAergic current in midbrain dopamine neurons is limited. To address this, we conducted whole‐cell recordings from ventral tegmental area (VTA) dopamine neurons in brain slices from mice. We found that application of GABA_A receptor antagonists decreased the holding current, indicating the presence of a tonic GABAergic input. Global increases in GABA release, induced by either a nitric oxide donor or inhibition of GABA uptake, further increased this tonic current. Importantly, prolonged inhibition of the firing activity of local GABAergic neurons abolished the tonic current. A combination of pharmacology and immunohistochemistry experiments suggested that, unlike common examples of tonic inhibition, this current may be mediated by a relatively unusual combination of α4βƐ subunits. Lastly, we found that the tonic current reduced excitability in dopamine neurons suggesting a subtractive effect on firing activity.

The Impact of Psychosis on Sexual Functioning: A Systematic Review

BACKGROUND

Sexual dysfunction among psychotic patients is highly prevalent. However, most research has focused on antipsychotic side effects on sexual functioning.

AIM

To provide evidence by means of a systematic review of the literature about the impact of psychosis on sexual functioning among unmedicated patients.

METHODS

Systematic search of MEDLINE (PubMed), Scopus, and Google Scholar for studies that reported sexual functioning among psychotic patients, who were drug-naïve or drug-free for at least 3 weeks before the study. Studies were published in English language between January 1994 and October 2019. We used the approach recommended by PRISMA, and the selection process was carried out by 2 reviewers.

OUTCOMES

The outcome measures were sexual function and sexual dysfunctions.

RESULTS

A total of 734 articles were obtained, 658 were obtained after duplicates were removed, 612 were excluded after reading the title and abstract, and 46 were included for a complete review of the articles. 5 papers were finally included. A total of 770 cases were included in the systematic review. The prevalence of sexual dysfunction in psychosis varied from 16.8% to 70% and in ultra-high state was 50%. It is noteworthy that those ultra-high-risk (prodromal) patients who develop psychosis had higher rates of sexual impairment. Therefore, we found higher rates of sexual dysfunction among untreated patients, both psychotic and ultra-high risk patients, than healthy controls.

CLINICAL IMPLICATIONS

The assessment of sexual behavior should be a part of routine psychiatric examination not only in psychotic but also in ultra-high-risk patients.

STRENGTHS & LIMITATIONS

This is the first systematic review about the impact of psychosis on sexual functioning among unmedicated patients. However, scarce and heterogeneous studies were identified.

CONCLUSIONS

Impaired sexual functioning is common in the onset of psychosis (or during ultra-high-risk state) and prior to the beginning of treatment. This suggests that psychotic symptoms and sexual dysfunction may have common etiological pathways at the psychosocial and neurobiological levels. Vargas-Cáceres S, Cera N, Nobre P, et al. The Impact of Psychosis on Sexual Functioning: A Systematic Review. J Sex Med 2021;18:457-466.

PDE10A Inhibitors-Clinical Failure or Window Into Antipsychotic Drug Action?

PDE10A, a phosphodiesterase that inactivates both cAMP and cGMP, is a unique signaling molecule in being highly and nearly exclusively expressed in striatal medium spiny neurons. These neurons dynamically integrate cortical information with dopamine-signaled value to mediate action selection among available behavioral options. Medium spiny neurons are components of either the direct or indirect striatal output pathways. Selective activation of indirect pathway medium spiny neurons by dopamine D2 receptor antagonists is putatively a key element in the mechanism of their antipsychotic efficacy. While PDE10A is expressed in all medium spiny neurons, studies in rodents indicated that PDE10A inhibition has behavioral effects in several key assays that phenocopy dopamine D2 receptor inhibition. This finding gave rise to the hypothesis that PDE10A inhibition also preferentially activates indirect pathway medium spiny neurons, a hypothesis that is consistent with electrophysiological, neurochemical, and molecular effects of PDE10A inhibitors. These data underwrote industry-wide efforts to investigate and develop PDE10A inhibitors as novel antipsychotics. Disappointingly, PDE10A inhibitors from 3 companies failed to evidence antipsychotic activity in patients with schizophrenia to the same extent as standard-of-care D2 antagonists. Given the notable similarities between PDE10A inhibitors and D2 antagonists, gaining an understanding of why only the latter class is antipsychotic affords a unique window into the basis for this therapeutic efficacy. With this in mind, we review the data on PDE10A inhibition as a step toward back-translating the limited antipsychotic efficacy of PDE10A inhibitors, hopefully to inform new efforts to develop better therapeutics to treat psychosis and schizophrenia.