Search Results (316)

The serotonergic system, originating in the raphe nuclei, differentially modulates the dorsal and ventral hippocampus, which are implicated in cognition and emotion, respectively. Emerging evidence from rodent models (e.g., neonatal ventral hippocampal lesion, pharmacological NMDA receptor antagonist exposure) and human postmortem studies indicates dorsoventral serotonergic alterations in schizophrenia. These data include elevated 5-HT1A receptor expression in the dorsal hippocampus, linking serotonergic hypofunction to cognitive deficits, and hyperactive 5-HT2A/3 receptor signaling and denser serotonergic innervation in the ventral hippocampus driving local hyperexcitability associated with psychosis and stress responsivity. These dorsoventral serotonergic alterations are shown to disrupt the excitation–inhibition balance, impair synaptic plasticity, and disturb network oscillations, as established by in vivo electrophysiology and functional imaging. Synthesizing these multi-level findings, we propose a novel “dorsoventral serotonin imbalance” model of schizophrenia, in which ventral hyperactivation predominantly contributes to psychotic symptoms and dorsal hypoactivity underlies cognitive deficits. We further highlight promising preclinical evidence that selective targeting of region- and receptor-specific targeting, using both pharmacological agents and emerging delivery technologies, may offer novel therapeutic opportunities enabling symptom-specific strategies in schizophrenia. Full article

The insular cortex has emerged as a key region implicated in a wide array of cognitive, emotional, and sensory processes. The anterior part of the insula (AIC) is central to emotional awareness, decision-making, and interoception, while the posterior insula (PIC) is more associated with somatosensory processing. The insula acts as a functional hub within the salience network and integrates homeostatic, affective, and cognitive information; thus, its role in different mental disorders seems to be prominent. Altered structure and connectivity of the insular cortex are evident in several psychiatric conditions. In schizophrenia, reductions in insular volume—especially on the left—correlate with hallucinations, emotional dysregulation, and cognitive deficits. Bipolar and major depressive disorders exhibit AIC volume loss and aberrant connectivity patterns linked to impaired affect regulation and interoceptive awareness. Anxiety disorders show functional hyperactivity of the insula, especially in response to fear-inducing stimuli, though findings on structural changes are mixed. Overall, growing evidence underscores the insular cortex’s central role in psychiatric pathophysiology and highlights its potential as a target for future diagnostic and therapeutic strategies. Full article

Over the past three turbulent decades, research has profoundly reshaped our understanding of chronic Toxoplasma gondii infection—traditionally regarded as harmless in immunocompetent individuals—unveiling its surprising impact on human health, performance, and behavior. This review emphasizes the effects of chronic Toxoplasma infection on physical and mental health, cognitive performance, and behavioral changes, highlighting key findings from studies investigating these domains, with a particular focus on both ultimate and proximate mechanisms underlying the observed effects. To this end, the primary focus will be on human studies; however, animal model studies will also be thoroughly considered when necessary and appropriate, to provide context and additional important information. Research demonstrates that chronic Toxoplasma infection may contribute to a broad spectrum of physical health issues. Ecological studies have revealed correlations between toxoplasmosis prevalence and increased morbidity and mortality from various conditions, including cardiovascular diseases, neurological disorders, and certain cancers. Large-scale cross-sectional studies have further shown that infected individuals report a higher incidence of numerous health complaints and diagnosed diseases, suggesting a significant impact on overall physical well-being. In addition to physical health, lifelong Toxoplasma infection (subclinical toxoplasmosis) has been implicated in cognitive impairments and behavioral changes. Studies have reported associations between infection and poorer performance in areas such as reaction time, processing speed, working memory, and executive function. Many of these behavioral changes likely relate to worsened health and a shift towards a “fast life history strategy.” These cognitive deficits can have significant implications for daily functioning and performance. Furthermore, the role of Toxoplasma infection in the development or exacerbation of mental health disorders has been extensively investigated. Meta-analyses, ecological studies, and large-scale observational studies have demonstrated associations between Toxoplasma infection and an increased risk of disorders such as schizophrenia and obsessive–compulsive disorder. While the precise mechanisms underlying these associations remain under investigation, research suggests that neuroinflammation and alterations in neurotransmitter systems are likely to play a role. Far from being harmless, subclinical toxoplasmosis is increasingly recognized as a hidden factor influencing human health, behavior, and cognitive performance—with implications that extend well beyond the individual to public health at large. Further research is warranted to elucidate the complex interplay between Toxoplasma infection, host physiology, and the development of various physical, cognitive, behavioral, and mental health conditions. Full article

Autistic traits—such as social communication deficits, cognitive rigidity, and repetitive behaviors—are increasingly recognized in individuals with schizophrenia, particularly in early-onset cases and subtypes with predominant negative symptoms. This overlap has prompted investigations into shared pathophysiological mechanisms. One emerging area of focus is the role of neuroinflammation in schizophrenia, which may contribute to the manifestation of autistic features. Immunological research indicates the presence of chronic low-grade inflammation, microglial activation, and disruption of the blood–brain barrier in schizophrenia. In particular, an imbalance in T-helper (Th) cell responses—specifically a shift toward Th2 dominance or concurrent Th1/Th2 activation—may lead to dysregulated cytokine production and disturbances in neural function. These findings highlight the importance of exploring immunological pathways as a basis for specific symptom profiles. Additionally, current efforts aim to identify reliable inflammatory biomarkers in schizophrenia that could support diagnosis, predict disease course, and guide treatment. Evaluating neuroinflammatory markers in patients with autistic features may provide novel insight into schizophrenia subtypes and help tailor immunomodulatory therapies. This review explores the expression of autistic traits in schizophrenia and examines the role of neuroinflammation and Th1/Th2 imbalance as potential mechanisms and biomarkers. Full article

Background/Objectives: Endocrine hormones play critical roles in regulating physiological processes, and previous studies have reported their associations with psychiatric disorders. Levels of endocrine hormones and the risk of developing psychiatric disorders are influenced by both genetic and non-genetic factors. However, the shared genetic basis underlying these associations remains largely unexplored. This study aims to dually evaluate the genetic correlations among endocrine hormones, including thyroid and sex hormones, as well as between endocrine hormone metrics and psychiatric disorders to identify potential shared genetic architectures. Methods: We obtained genome-wide association study summary statistics for six thyroid hormone metrics, three sex hormone metrics, and ten psychiatric disorders from predominantly European-ancestry populations. Genetic correlations were computed using linkage disequilibrium score regression after harmonizing variant data to ensure consistency across studies. Results: Significant genetic correlations were observed among thyroid and sex hormone metrics, indicating a strong shared genetic basis. Sex hormones exhibited multiple genetic correlations with psychiatric disorders, including negative correlations between sex hormone-binding globulin and attention-deficit hyperactivity disorder (ADHD) (p = 3.95 × 10⁻¹²) and major depressive disorder (p = 4.67 × 10⁻⁵), and positive genetic correlations with anorexia nervosa (p = 2.86 × 10⁻¹²) and schizophrenia (p = 2.00 × 10⁻⁴). Testosterone and estradiol had negative genetic correlations with ADHD and major depressive disorder, while testosterone had positive genetic correlations with anorexia nervosa and schizophrenia. Although thyroid hormone metrics did not exhibit Bonferroni-significant genetic correlations, nominal associations were observed, such as a negative genetic correlation between thyroid-stimulating hormone and major depressive disorder (p = 2.33 × 10⁻²). Conclusions: These findings suggest a shared genetic basis between endocrine hormones and psychiatric disorders, particularly for sex hormones. Future studies leveraging larger, more diverse populations are warranted to validate and extend the genetic correlations observed in this study. Full article

Introduction: Cerebellar transcranial magnetic stimulation (TMS) has emerged as a promising neuromodulatory intervention for addressing motor, cognitive, and socio-affective deficits across a range of clinical populations. Materials and Methods: This systematic review aimed to synthesize recent evidence (2015–2025) on the efficacy, safety, and methodological characteristics of multi-session cerebellar TMS protocols used in rehabilitation settings. Following PRISMA guidelines, a comprehensive search of PubMed and Scopus was conducted to identify peer-reviewed studies applying multi-session cerebellar TMS in clinical populations for motor, cognitive, or affective rehabilitation. A total of 1750 records were screened, and 46 studies met the inclusion criteria. Data extraction included sample characteristics, study design, TMS protocol, targeted symptoms, outcomes, and risk of bias. Results: The results show that repeated sessions of cerebellar TMS are safe, well-tolerated, and associated with functional improvements primarily in motor disorders—such as spinocerebellar ataxia, Parkinson’s disease, multiple system atrophy, essential tremor, and post-stroke deficits—as well as in psychiatric populations, particularly patients with schizophrenia. Discussion: Evidence regarding the effects of cerebellar TMS on cognitive functions remains limited, though promising. Despite overall positive findings, the literature is limited by variability in stimulation parameters, protocol designs, and outcome measures, small sample sizes and potential publication bias. Conclusions: The review highlights the need for further large-scale and well-controlled trials to refine stimulation protocols, explore long-term effects, and clarify the underlying mechanisms of cerebellar TMS across motor, cognitive, and affective domains. This systematic review has been registered on PROSPERO (registration number: CRD420251067308). Full article

Background/Objectives: Schizophrenia Spectrum Disorders (SSDs) carry a debilitating burden of disease which, even after pharmacological and psychological treatment are optimized, remains difficult to fully target. New online-delivered and user-led interventions may provide an appropriate, cost-effective answer to this problem. This study aims to retrieve the currently gathered findings on the efficacy of these interventions across several outcomes, such as symptom severity, social cognition, functioning and others. Methods: A systematic review of the current available literature was conducted. Of 29 potentially relevant articles, 26 were included and assigned at least one of four intervention types: Web-Based Therapy (WBT), Web-Based Psycho-Education (WBP), Online Peer Support (OPS) and Prompt-Based Intervention (PBI). Results: The findings were grouped based on outcome. Of 24 studies evaluating the effects of symptom severity, 14 have achieved statistically significant results, and 10 have not. WBT (such as online-delivered Cognitive Behavioral Therapy, Acceptance and Commitment Therapy, social cognition training and Mindfulness Training) seemed to be the most effective at targeting symptoms. Of 14 studies evaluating functioning, seven achieved significant results, four involving a form of social or neurocognitive training, suggesting a potential pathway towards functional improvements through interventions targeting cognition and motivation. Regarding social cognition, all seven studies measuring the effects of an intervention on this outcome produced significant results, indicating that this outcome lends itself well to remote, online administration. This may be linked with the nature of social cognition exercises, as they are commonly administered through a digital medium (such as pictures, videos and auditory exercises), a delivery method that suits the online-user led model very well. Conclusions: Online user-led interventions show promise as a new way to tackle functional deficits in SSD patients and achieve these improvements through targeting social cognition, a hard-to-reach component of the burden of SSDs which seems to be successfully targetable in a remote, user-led fashion. Symptomatic improvements can also be achievable, through the combination of these interventions with treatment as usual. Full article

Kynurenic acid (KYNA), a putative neuroprotective agent, modulates glutamatergic pathways in schizophrenia and Parkinson’s disease but is limited by acute motor activity impairments (e.g., ataxia). Research leveraging animal disease models explores its structure–activity relationship to enhance therapeutic efficacy while mitigating adverse effects, addressing global neuropsychiatric disorders affecting over 1 billion people. Structural analogs of KYNA (SZR-72, SZR-73, and SZR-81) were designed to uncouple therapeutic benefits from motor toxicity; yet, systematic comparisons of their acute behavioral profiles remain unexplored. Here, we assess the motor safety, time-dependent effects, and therapeutic potential of these analogs in mice. Using acute intracerebroventricular dosing, we evaluated motor coordination (rotarod), locomotor activity (open-field), and stereotypic behaviors. KYNA induced significant ataxia and stereotypic behaviors at 15 min, resolving by 45 min. In contrast, all analogs avoided acute motor deficits, with SZR-73 maintaining baseline rotarod performance and eliciting a delayed decrease in ambulation and inquisitiveness in open-field assays. These findings demonstrate that the structural optimization of KYNA successfully mitigates motor toxicity while retaining neuromodulatory activity. Here, we show that SZR-73 emerges as a lead candidate, combining transient therapeutic effects with preserved motor coordination. This study advances the development of safer neuroactive compounds, bridging a critical gap between preclinical innovation and clinical translation. Future work must validate chronic efficacy, disease relevance, and mechanistic targets to harness the full potential of KYNA analogs in treating complex neuropsychiatric disorders. Full article

Mirror neurons (MNs), a set of neurons that are activated during the processes of observation and execution of actions, have drawn significant attention in the research of neurodegenerative and psychological disorders. Research in the field of Autism Spectrum Disorder (ASD) and schizophrenia demonstrates evidence in favour of common underlying neural mechanisms underlying the two conditions, especially with respect to mu rhythm suppression, a proxy for MN activation and socio-cognitive impairments. This paper aims to review the most recent studies on the neurological underpinnings of social cognition deficits and cognitive discrepancies shared by ASD and schizophrenia, as detected by measuring the functionality and activation of the mirror neuron system. The findings of the review reveal a lack of consensus with respect to the validity of the “broken mirror” theory. The review also shows that further research is warranted to shed light on the implications of mirror neuron dysfunction in neuropsychiatric conditions and assist the development of technological interventions and treatments. Full article

Oligodendrocyte precursor cells (OPCs) are a dynamic and heterogeneous population of glial cells essential for brain development and myelination. Beyond their well-established role in oligodendrogenesis, emerging evidence suggests that OPCs contribute to synaptic regulation, neuronal communication, and brain plasticity. Recent studies have increasingly implicated OPC dysfunction in the pathophysiology of psychiatric disorders, particularly schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD). This narrative review integrates clinical, genetic, transcriptomic, and histological findings to examine the role of OPC alterations in mental illnesses. In SCZ, OPC abnormalities predominantly affect myelination, but recent data also suggest deficits in non-canonical functions, including neuron–OPC communication. Findings in BD largely mirror those in SCZ, implying shared OPC-related mechanisms across these disorders. In contrast, OPC involvement in MDD appears more complex, with evidence supporting both myelination deficits and non-canonical dysfunctions, such as impaired neuro–glial interactions and perineuronal network alterations. The developmental timing of OPC dysfunction may represent a common denominator underlying psychiatric disorders, as early-life stress and neurodevelopmental disturbances have been linked to OPC impairments. Moreover, given the shared developmental origins of OPCs and parvalbumin-positive interneurons, disruptions in their mutual interactions may contribute to broader neural network dysregulation. Despite these insights, the field remains in its infancy. Future studies integrating independent human cohorts with robust preclinical models are needed to clarify the extent of OPC involvement in psychiatric pathophysiology. Understanding OPC dysfunction may reveal novel biomarkers and open new avenues for individualized therapeutic interventions and preventive strategies in mental health. Full article

Background and Objectives: Neuropsychiatric disorders, including schizophrenia, bipolar disorder, and major depression, constitute a leading global public health challenge due to their high prevalence, chronicity, and profound cognitive and functional impact. This systematic review explores the role of electroencephalography (EEG)-based cognitive biomarkers in improving the understanding, diagnosis, monitoring, and treatment of these conditions. It evaluates how EEG-derived markers can reflect neuro-cognitive dysfunction and inform personalized and scalable mental health interventions. Materials and Methods: A systematic review was conducted following PRISMA guidelines. The databases searched included PubMed, Scopus, PsycINFO, and Web of Science for peer-reviewed empirical studies published between 2014 and 2025. Inclusion criteria focused on EEG-based investigations in clinical populations with neuropsychiatric diagnoses, emphasizing studies that assessed associations with cognitive function, symptom severity, treatment response, or functional outcomes. Of the 447 initially identified records, 132 studies were included in the final synthesis. Results: This review identifies several EEG markers—such as mismatch negativity (MMN), P300, frontal alpha asymmetry, and theta/beta ratios—as reliable indicators of cognitive impairments across psychiatric populations. These biomarkers are associated with deficits in attention, memory, and executive functioning, and show predictive utility for treatment outcomes and disease progression. Methodological trends indicate an increasing use of machine learning and multimodal neuroimaging integration to enhance diagnostic specificity. While many studies exhibit moderate risk of bias, the overall findings support EEG biomarkers’ reproducibility and translational relevance. Conclusions: EEG-based cognitive biomarkers offer a valuable, non-invasive means of capturing the neurobiological underpinnings of psychiatric disorders. Their diagnostic and prognostic potential, as well as high temporal resolution and portability, supports their use in clinical and public health contexts. The field, however, requires further standardization, cross-validation, and investment in scalable applications. Advancing EEG biomarker research holds promise for precision psychiatry and proactive mental health strategies at the population level. Full article

In animal models, ketamine, a non-competitive N-methyl-D-aspartate (NMDA) antagonist, induces schizophrenia-like symptoms, such as positive and negative symptoms, as well as cognitive deficits. In the present study, we evaluated the behavioral responses and the number of EODs (electric organ discharges) of the weakly electric fish Gnathonemus petersii using the novel object recognition task (NORT). We aimed to investigate whether pharmacological modulation of the glutamatergic system would impair cognitive functions by administering the NMDA receptor antagonist ketamine, and whether these impairments could be suppressed by the administration of typical (first-generation) and atypical (second-generation) antipsychotics—clozapine and haloperidol, respectively. G. petersii preferred the familiar object over the novel object in the NORT paradigm. Although no significant differences were observed when exploring the two identical objects during the training session, the fish spent less time, moved a shorter distance, and emitted fewer EODs in the testing phase with the novel object. No direct relationship was detected between the EODs and behavioral responses to the administration of ketamine and typical antipsychotics. Ketamine administered with atypical antipsychotic clozapine disrupted the perception of the original object, where one of the objects was preferred. In the novel object trial, the time spent on the original and new objects was attenuated to the same level. Full article

Background: Cognitive impairment is a common feature of schizophrenia spectrum disorders and has been associated with functional disruption preceding the onset of psychosis. Understanding how cognitive deficits interact with clinical symptoms and functioning in early psychosis remains challenging. In this study, we aim to investigate whether a distinct “cognitive signature” characterizes functional disruption at the onset of psychosis. Material and Methods: Clinical, cognitive, and functional data were collected from 101 first episode psychosis patients at their first hospitalization. Stepwise regression models were used to identify predictors of global functioning and symptom severity at the time of onset, as well as diagnostic outcomes at discharge. Path analysis was used to explore the relationship among symptom severity, cognition, and functional outcomes. Results: Deficits in visual memory were selectively predictive of lower functioning and higher global symptom severity at the time of psychosis onset. Reduced visual-spatial abilities were also associated with unemployment at the time preceding hospitalization and predicted a non-affective schizophrenia spectrum diagnosis at discharge. Path analysis found that visual memory fully mediated the relationship between negative symptoms and level of functioning. Conclusions: Impairment in visual cognition seems to be uniquely associated with functional impairment and global symptom severity at the onset of psychosis and to mediate the relationship between negative symptoms and functioning. The results might indicate a primary relevance of visual cognitive aspects in marking functional disruption and symptom exacerbation at psychosis onset. This might have implications for early detection and inform treatment plans. Full article

Schizophrenia (SCZ) is a severe, chronic mental disorder of unknown etiology and limited therapeutic options. Bioenergetic deficits in the oxidative phosphorylation system (OXPHOS) during early postnatal brain development may underlie disrupted neuronal metabolism and synaptic signaling, contributing to the neurodevelopmental and behavioral disturbances observed in patients. This narrative review summarizes updated evidence linking mitochondrial-OXPHOS dysfunction to SCZ pathophysiology. The novelty lies in the focus on OXPHOS dysfunction at the enzymatic/functional level, rather than on genetic, transcriptional, or oxidative parameters. While complex I impairment has long been highlighted and proposed as a peripheral marker of the disease, recent studies also report alterations in other OXPHOS complexes and their precursors. These findings suggest that OXPHOS dysfunction is not isolated to a single enzymatic component but affects broader mitochondrial function, alongside oxidative stress, contributing to disease progression through mechanisms involving apoptosis, accelerated aging, and synaptic deterioration. OXPHOS dysfunction in both central and peripheral tissues further supports its relevance to SCZ. Overall, the literature points to mitochondrial OXPHOS abnormalities as a significant biological feature of SCZ. Whether these alterations are causal factors or consequences of disease processes remains unclear. Understanding OXPHOS dysregulation may open new avenues for targeted therapies. Full article

Schizophrenia is a complex neuropsychiatric disorder composed of primary cluster-positive symptoms, negative symptoms, disorganization, neurocognitive deficits, and social cognitive impairments. While traditional antipsychotics primarily target dopamine pathways, they provide limited efficacy against cognitive deficits and negative symptoms. Growing evidence implicates glutamatergic dysregulation, particularly N-methyl-D-aspartate receptor (NMDA-R) hypofunction, in the pathophysiology of schizophrenia, making glutamate modulation a promising therapeutic approach. This review explores emerging glutamate-based treatment strategies, including NMDA receptor modulators, metabotropic glutamate receptor (mGluR) agents, glutamate transporter regulators, and kynurenine pathway inhibitors. We summarize preclinical and clinical findings on NMDA co-agonists (D-serine and glycine), glycine transporter inhibitors, D-amino acid oxidase inhibitors, and mGluR-targeted therapies, highlighting their mechanisms, efficacy, and limitations. In addition, we discuss novel interventions aimed at restoring glutamate homeostasis, including neuroinflammatory modulation and synaptic plasticity enhancers. Despite promising results, many glutamate-targeting therapies have yielded inconsistent clinical outcomes, underscoring the need for biomarker-driven patient selection and optimized treatment protocols. We propose that integrating glutamate modulators with existing antipsychotic regimens may enhance therapeutic response while minimizing side effects. Future research should focus on refining glutamate-based interventions, identifying predictive biomarkers, and addressing the heterogeneity in schizophrenia pathology. With continued advancements, glutamate modulation has the potential to transform schizophrenia treatment, particularly for cognitive and negative symptoms that remain largely unaddressed by current therapies. Full article