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1.
Schizophr Bull ; 2024 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-38451304

RESUMO

This article describes the rationale, aims, and methodology of the Accelerating Medicines Partnership® Schizophrenia (AMP® SCZ). This is the largest international collaboration to date that will develop algorithms to predict trajectories and outcomes of individuals at clinical high risk (CHR) for psychosis and to advance the development and use of novel pharmacological interventions for CHR individuals. We present a description of the participating research networks and the data processing analysis and coordination center, their processes for data harmonization across 43 sites from 13 participating countries (recruitment across North America, Australia, Europe, Asia, and South America), data flow and quality assessment processes, data analyses, and the transfer of data to the National Institute of Mental Health (NIMH) Data Archive (NDA) for use by the research community. In an expected sample of approximately 2000 CHR individuals and 640 matched healthy controls, AMP SCZ will collect clinical, environmental, and cognitive data along with multimodal biomarkers, including neuroimaging, electrophysiology, fluid biospecimens, speech and facial expression samples, novel measures derived from digital health technologies including smartphone-based daily surveys, and passive sensing as well as actigraphy. The study will investigate a range of clinical outcomes over a 2-year period, including transition to psychosis, remission or persistence of CHR status, attenuated positive symptoms, persistent negative symptoms, mood and anxiety symptoms, and psychosocial functioning. The global reach of AMP SCZ and its harmonized innovative methods promise to catalyze the development of new treatments to address critical unmet clinical and public health needs in CHR individuals.

2.
Neuroimage Clin ; 41: 103570, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38309185

RESUMO

Impaired motion perception in schizophrenia has been associated with deficits in social-cognitive processes and with reduced activation of visual sensory regions, including the middle temporal area (MT+) and posterior superior temporal sulcus (pSTS). These findings are consistent with the recent proposal of the existence of a specific 'third visual pathway' specialized for social perception in which motion is a fundamental component. The third visual pathway transmits visual information from early sensory visual processing areas to the STS, with MT+ acting as a critical intermediary. We used functional magnetic resonance imaging to investigate functioning of this pathway during processing of naturalistic videos with explicit (real) motion and static images with implied motion cues. These measures were related to face emotion recognition and motion-perception, as measured behaviorally. Participants were 28 individuals with schizophrenia (Sz) and 20 neurotypical controls. Compared to controls, individuals with Sz showed reduced activation of third visual pathway regions (MT+, pSTS) in response to both real- and implied-motion stimuli. Dysfunction of early visual cortex and pulvinar were also associated with aberrant real-motion processing. Implied-motion stimuli additionally engaged a wide network of brain areas including parietal, motor and frontal nodes of the human mirror neuron system. The findings support concepts of MT+ as a mediator between visual sensory areas and higher-order brain and argue for greater focus on MT+ contributions to social-cognitive processing, in addition to its well-documented role in visual motion processing.


Assuntos
Percepção de Movimento , Esquizofrenia , Humanos , Esquizofrenia/diagnóstico por imagem , Vias Visuais/diagnóstico por imagem , Lobo Temporal , Encéfalo/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Mapeamento Encefálico , Percepção de Movimento/fisiologia , Estimulação Luminosa/métodos
3.
Schizophr Res Cogn ; 36: 100302, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38323136

RESUMO

Background: Cognitive alterations have been reported in early stages of psychosis including people with First Episode Psychosis (FEP), Clinical High-Risk Mental State (CHR), and Psychotic-Like Experience (PLE). This study aimed to compare the cognitive function in early stages of psychosis using the Montreal Cognitive Assessment (MoCA), a low-cost and brief assessment tool of cognitive functions. Methods: A total of 154 individuals, including 35 with FEP, 38 CHR, 44 PLE, and 37 healthy controls (HC), were evaluated with the MoCA in Santiago, Chile. We calculated the mean total score of the MoCA and the standard deviation of the mean. Groups were assessed for a trend to lower scores in a pre-determined sequence (HC > PLE > CHR > FEP) using the Jonckheere-Terpstra test (TJT). Results: The mean total MoCA scores were 24.8 ± 3.3 in FEP, 26.4 ± 2.4 in CHR, 26.4 ± 2.3 in PLE, and 27.2 ± 1.8 in HC. The analyses revealed a significant trend (p < 0.05) toward lower MoCA individual domain scores and MoCA total scores in the following order: HC > PLE > CHR > FEP. The mean total scores of all groups were above the cut-off for cognitive impairment (22 points). Conclusions: The MoCA describes lower scores in cognition across early stages of psychosis and may be a useful low-cost assessment instrument in early intervention centers of poorly resourced settings.

4.
Artigo em Inglês | MEDLINE | ID: mdl-37641537

RESUMO

AIM: To harmonize two ascertainment and severity rating instruments commonly used for the clinical high risk syndrome for psychosis (CHR-P): the Structured Interview for Psychosis-risk Syndromes (SIPS) and the Comprehensive Assessment of At-Risk Mental States (CAARMS). METHODS: The initial workshop is described in the companion report from Addington et al. After the workshop, lead experts for each instrument continued harmonizing attenuated positive symptoms and criteria for psychosis and CHR-P through an intensive series of joint videoconferences. RESULTS: Full harmonization was achieved for attenuated positive symptom ratings and psychosis criteria, and modest harmonization for CHR-P criteria. The semi-structured interview, named Positive SYmptoms and Diagnostic Criteria for the CAARMS Harmonized with the SIPS (PSYCHS), generates CHR-P criteria and severity scores for both CAARMS and SIPS. CONCLUSIONS: Using the PSYCHS for CHR-P ascertainment, conversion determination, and attenuated positive symptom severity rating will help in comparing findings across studies and in meta-analyses.

5.
medRxiv ; 2023 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-37461678

RESUMO

Background and Hypothesis: Motion processing deficits in schizophrenia have been linked to impairments in higher-order social-cognitive processes. The neural underpinnings are not fully understood but it has been hypothesized that middle temporal area (MT+) may serve as a bridge between purely sensory and more cognitive proceseses. We investigated the interrelationship between MT+ sensory processing deficits and impairments in higher-order processing using naturalistic videos with explicit motion and static images with implied-motion cues. Study Design: Functional magnetic resonance imaging was used to evaluate cortical and subcortical brain regions associated with real- and implied-motion processing in 28 individuals with schizophrenia and 20 neurotypical controls. These measures were related to face emotion recognition and motion-perception deficits, as measured behaviorally. Study Results: Activation of MT+ was abnormal in schizophrenia during both real- and implied-motion processing. Dysfunction of early visual cortex and pulvinar were also associated with impaired real-motion processing. During implied-motion-perception, MT+ participated in a wider network involving sensorimotor and prefrontal nodes of the human mirror neuron system, known to play a role in social-cognitive processes. Perception of both real- and implied-motion engaged the posterior superior temporal sulcus, a key node of the social brain network. Conclusions: The findings support concepts of MT+ as a bridge between visual sensory areas and higher-order brain regions especially in relationship to face emotion recognition and social cognition. Our data argue for greater focus on MT+ contributions to social-cognitive processing, in addition to its well-documented role in visual motion processing.

6.
Schizophrenia (Heidelb) ; 8(1): 53, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35853943

RESUMO

Automated language analysis of speech has been shown to distinguish healthy control (HC) vs chronic schizophrenia (SZ) groups, yet the predictive power on first-episode psychosis patients (FEP) and the generalization to non-English speakers remain unclear. We performed a cross-sectional and longitudinal (18 months) automated language analysis in 133 Spanish-speaking subjects from three groups: healthy control or HC (n = 49), FEP (n = 40), and chronic SZ (n = 44). Interviews were manually transcribed, and the analysis included 30 language features (4 verbal fluency; 20 verbal productivity; 6 semantic coherence). Our cross-sectional analysis showed that using the top ten ranked and decorrelated language features, an automated HC vs SZ classification achieved 85.9% accuracy. In our longitudinal analysis, 28 FEP patients were diagnosed with SZ at the end of the study. Here, combining demographics, PANSS, and language information, the prediction accuracy reached 77.5% mainly driven by semantic coherence information. Overall, we showed that language features from Spanish-speaking clinical interviews can distinguish HC vs chronic SZ, and predict SZ diagnosis in FEP patients.

7.
Front Psychiatry ; 12: 662407, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34220575

RESUMO

Brain Derived Neurotrophic Factor (BDNF) has been linked to cognitive symptoms of schizophrenia, which has been documented in previous reviews by several authors. However, a trend has recently emerged in this field moving from studying schizophrenia as a disease to studying psychosis as a group. This review article focuses on recent BDNF studies in relation to cognition in human subjects during different stages of the psychotic process, including subjects at high risk of developing psychosis, patients at their first episode of psychosis, and patients with chronic schizophrenia. We aim to provide an update of BDNF as a biomarker of cognitive function on human subjects with schizophrenia or earlier stages of psychosis, covering new trends, controversies, current research gaps, and suggest potential future developments in the field. We found that most of current research regarding BDNF and cognitive symptoms in psychosis is done around schizophrenia as a disease. Therefore, it is necessary to expand the study of the relationship between BDNF and cognitive symptoms to psychotic illnesses of different stages and origins.

8.
Front Behav Neurosci ; 15: 787383, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-35237135

RESUMO

One important aspect for managing social interactions is the ability to perceive and respond to facial expressions rapidly and accurately. This ability is highly dependent upon intact processing within both cortical and subcortical components of the early visual pathways. Social cognitive deficits, including face emotion recognition (FER) deficits, are characteristic of several neuropsychiatric disorders including schizophrenia (Sz) and autism spectrum disorders (ASD). Here, we investigated potential visual sensory contributions to FER deficits in Sz (n = 28, 8/20 female/male; age 21-54 years) and adult ASD (n = 20, 4/16 female/male; age 19-43 years) participants compared to neurotypical (n = 30, 8/22 female/male; age 19-54 years) controls using task-based fMRI during an implicit static/dynamic FER task. Compared to neurotypical controls, both Sz (d = 1.97) and ASD (d = 1.13) participants had significantly lower FER scores which interrelated with diminished activation of the superior temporal sulcus (STS). In Sz, STS deficits were predicted by reduced activation of early visual regions (d = 0.85, p = 0.002) and of the pulvinar nucleus of the thalamus (d = 0.44, p = 0.042), along with impaired cortico-pulvinar interaction. By contrast, ASD participants showed patterns of increased early visual cortical (d = 1.03, p = 0.001) and pulvinar (d = 0.71, p = 0.015) activation. Large effect-size structural and histological abnormalities of pulvinar have previously been documented in Sz. Moreover, we have recently demonstrated impaired pulvinar activation to simple visual stimuli in Sz. Here, we provide the first demonstration of a disease-specific contribution of impaired pulvinar activation to social cognitive impairment in Sz.

10.
Early Interv Psychiatry ; 13(2): 328-334, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30548415

RESUMO

AIM: Early detection and intervention (EDI) is a main challenge in psychosis research. The Chilean schizophrenia (SZ) national program has universal support and treatment by law for all SZ patients, but this does not yet extend to earlier stages of illness. Therefore, we have piloted an ultra-high risk (UHR) program to demonstrate the utility and feasibility of this public health approach in Chile. METHODS: We introduce "The University of Chile High-risk Intervention Program," which is the first national EDI program for UHR youths. Longitudinal follow-up included clinical and cognitive assessments, and monitoring of physiological sensory and cognitive indices, through electroencephalographic techniques. RESULTS: We recruited 27 UHR youths over 2 years. About 92.6% met criteria for attenuated psychosis syndrome (APS). Mean Scale of Psychosis-Risk Symptoms (SOPS) ratings in the cohort were 6.9 (SD 4.6) for positive, 9.1 (SD 8.3) for negative, 5.4 (SD 5.3) for disorganized and 6.3 (SD 4.1) for general symptoms. About 14.8% met criteria for comorbid anxiety disorders and 44.4% for mood disorders. Most participants received cognitive behavioural therapy (62.9%) and were prescribed low dose antipsychotics (85.2%). The transition rate to psychosis was 22% within 2 years. CONCLUSIONS: We describe our experience in establishing the first EDI program for UHR subjects in Chile. Our cohort is similar in profile and risk to those identified in higher-income countries. We will extend our work to further optimize psychosocial and preventive interventions, to promote its inclusion in the Chilean SZ national program and to establish a South American collaboration network for SZ research.


Assuntos
Pesquisa Biomédica , Diagnóstico Precoce , Escalas de Graduação Psiquiátrica/estatística & dados numéricos , Transtornos Psicóticos/diagnóstico , Transtornos Psicóticos/psicologia , Esquizofrenia/diagnóstico , Psicologia do Esquizofrênico , Adolescente , Adulto , Antipsicóticos/uso terapêutico , Pesquisa Biomédica/tendências , Chile , Terapia Cognitivo-Comportamental , Estudos de Coortes , Comorbidade , Substituição de Medicamentos , Intervenção Médica Precoce , Feminino , Humanos , Masculino , Sintomas Prodrômicos , Transtornos Psicóticos/terapia , Esquizofrenia/terapia , Adulto Jovem
11.
Am J Psychiatry ; 175(12): 1243-1254, 2018 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-30278791

RESUMO

OBJECTIVE: The ability to perceive the motion of biological objects, such as faces, is a critical component of daily function and correlates with the ability to successfully navigate social situations (social cognition). Deficits in motion perception in schizophrenia were first demonstrated about 20 years ago but remain understudied, especially in the early, potentially prodromal, stages of the illness. The authors examined the neural bases of visual sensory processing impairments, including motion, in patients with schizophrenia (N=63) and attenuated psychosis (clinical high risk) (N=32) compared with age-matched healthy control subjects (N=67). METHOD: Electrophysiological recordings during stimulus and motion processing were analyzed using oscillatory (time frequency) approaches that differentiated motion-onset-evoked activity from stimulus-onset sensory-evoked responses. These were compared with functional MRI (fMRI) measures of motion processing. RESULTS: Significant deficits in motion processing were observed across the two patient groups, and these deficits predicted impairments in both face-emotion recognition and cognitive function. In contrast to motion processing, sensory-evoked stimulus-onset responses were intact in patients with attenuated psychosis, and, further, the relative deficit in motion-onset responses compared with stimulus-onset responses predicted transition to schizophrenia. In patients with schizophrenia, motion detection deficits mapped to impaired activation in motion-sensitive visual cortex during fMRI. Additional visual impairments in patients with schizophrenia, not present in patients with attenuated psychosis, implicated other visual regions, including the middle occipital gyrus and pulvinar thalamic nucleus. CONCLUSIONS: The study findings emphasize the importance of sensory-level visual dysfunction in the etiology of schizophrenia and in the personal experience of individuals with the disorder and demonstrate that motion-processing deficits may predate illness onset and contribute to impaired function even in patients with attenuated psychosis.


Assuntos
Percepção de Movimento , Esquizofrenia/fisiopatologia , Adulto , Encéfalo/fisiopatologia , Estudos de Casos e Controles , Eletroencefalografia , Potenciais Evocados Visuais , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Neuroimagem , Testes Neuropsicológicos , Sintomas Prodrômicos , Escalas de Graduação Psiquiátrica , Síndrome , Córtex Visual/fisiopatologia , Adulto Jovem
12.
Am J Med Genet B Neuropsychiatr Genet ; 174(7): 663-670, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28901686

RESUMO

Schizophrenia (SZ) is a disorder with a high heritability and a complex architecture. Several dozen genetic variants have been identified as risk factors through genome-wide association studies including large population-based samples. However, the bulk of the risk cannot be accounted for by the genes associated to date. Rare mutations have been historically seen as relevant only for some infrequent, Mendelian forms of psychosis. Recent findings, however, show that the subset of patients that present a mutation with major effect is larger than expected. We discuss some of the molecular findings of these studies. SZ is clinically and genetically heterogeneous. To identify the genetic variation underlying the disorder, research should be focused on features that are more likely a product of genetic heterogeneity. Based on the phenotypical correlations with rare variants, cognition emerges as a relevant domain to study. Cognitive disturbances could be useful in selecting cases that have a higher probability of carrying deleterious mutations, as well as on the correct ascertainment of sporadic cases for the identification of de novo variants.


Assuntos
Marcadores Genéticos , Predisposição Genética para Doença , Variação Genética , Esquizofrenia/genética , Genótipo , Humanos , Fenótipo
13.
Neurotoxicol Teratol ; 62: 13-19, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28579518

RESUMO

Chronic exposure to organophosphate pesticides is a worldwide public health concern associated with several psychiatric disorders and dementia. Most existing studies on the effects of pesticides only evaluate agricultural workers. Therefore, this study sought to establish if individuals indirectly exposed to pesticides, such as residents in agricultural areas, also suffer cognitive impairments. Neuropsychological evaluations were carried out on three groups (n=102): agricultural workers directly exposed to pesticides (n=32), individuals living in agricultural areas indirectly (i.e. environmentally) exposed to pesticides (n=32), and an unexposed control group (n=38). The assessed cognitive processes included memory, executive functions, attention, language praxis, and visuoconstruction. The direct exposure group performed significantly lower in executive function, verbal fluency, and visual and auditory memory tests than the indirect exposure group, which, in turn, performed worse than the unexposed group. Even after adjusting for age, gender, and educational level, both exposure groups showed higher rates of cognitive deficit than control individuals. In conclusion, both direct and indirect chronic exposure to pesticides affects cognitive functioning in adults and, consequently, actions should be taken to protect the health of not only agricultural workers, but also of residents in agricultural areas.


Assuntos
Doenças dos Trabalhadores Agrícolas/induzido quimicamente , Disfunção Cognitiva/induzido quimicamente , Exposição Ambiental/efeitos adversos , Praguicidas/efeitos adversos , Adulto , Chile , Estudos Transversais , Fazendeiros/psicologia , Feminino , Humanos , Masculino , Testes Neuropsicológicos , Exposição Ocupacional/efeitos adversos
14.
Trials ; 18(1): 233, 2017 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-28545578

RESUMO

BACKGROUND: According to the projections of the World Health Organization, 15% of all disabilities will be associated with mental illnesses by 2020. One of the mental disorders with the largest social impacts due to high personal and family costs is psychosis. Among the most effective psychological approaches to treat schizophrenia and other psychotic disorders at the world level is cognitive behavioral therapy. Recently, cognitive behavioral therapy has introduced several tools and strategies that promote psychological processes based on acceptance and mindfulness. A large number of studies support the effectiveness of mindfulness in dealing with various mental health problems, including psychosis. This study is aimed at determining the efficiency of a mindfulness-based program in increasing cognitive function and psychological well-being in patients with a first episode of schizophrenia and a high risk mental state (those at risk of developing an episode of psychosis). METHODS AND DESIGN: This is an experimentally designed, multi-center randomized controlled trial, with a 3-month follow-up period. The study participants will be 48 patients diagnosed with schizophrenia (first episode) and 48 with a high-risk mental state, from Santiago, Chile, aged between 15 and 35 years. Participants will be submitted to a mindfulness-based intervention (MBI), which will involve taking part in eight mindfulness workshops adapted for people with psychosis. Workshops will last approximately 1.5 hours and take place once a week, over 8 weeks. The primary outcome will be the cognitive function through Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) and the secondary outcome will be psychological well-being measured by self-reporting questionnaires. DISCUSSION: The outcomes of this trial will add empirical evidence to the benefits and feasibility of MBIs for the psychotherapeutic treatment of patients with schizophrenia and high-risk mental states in reducing cognitive impairment in attention, working memory, and social cognition, as well as increasing the psychological well-being by empowering the patients' personal resources in the management of their own symptoms and psychotic experiences. TRIAL REGISTRATION: ISRCTN registration number ISRCTN24327446 . Registered on 12 September 2016.


Assuntos
Cognição , Terapia Cognitivo-Comportamental/métodos , Intervenção Médica Precoce , Saúde Mental , Atenção Plena , Esquizofrenia/terapia , Psicologia do Esquizofrênico , Adolescente , Adulto , Atenção , Chile , Protocolos Clínicos , Feminino , Humanos , Masculino , Memória , Escalas de Graduação Psiquiátrica , Projetos de Pesquisa , Fatores de Risco , Esquizofrenia/diagnóstico , Autorrelato , Comportamento Social , Fatores de Tempo , Resultado do Tratamento , Adulto Jovem
15.
Front Neurosci ; 10: 488, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27877101

RESUMO

Metabolic syndrome (MS) is a prevalent and severe comorbidity observed in schizophrenia (SZ). The exact nature of this association is controversial and very often accredited to the effects of psychotropic medications and disease-induced life-style modifications, such as inactive lifestyle, poor dietary choices, and smoking. However, drug therapy and disease-induced lifestyle factors are likely not the only factors contributing to the observed converging nature of these conditions, since an increased prevalence of MS is also observed in first episode and drug-naïve psychosis populations. MS and SZ share common intrinsic susceptibility factors and etiopathogenic mechanisms, which may change the way we approach clinical management of SZ patients. Among the most relevant common pathogenic pathways of SZ and MS are alterations in the sphingolipids (SLs) metabolism and SLs homeostasis. SLs have important structural functions as they participate in the formation of membrane "lipid rafts." SLs also play physiological roles in cell differentiation, proliferation, and inflammatory processes, which might be part of MS/SZ common pathophysiological processes. In this article we review a plausible mechanism to explain the link between MS and SZ through a disruption in SL homeostasis. Additionally, we provide insights on how this hypothesis can lead to the developing of new diagnostic/therapeutic technologies for SZ patients.

16.
Pharmacol Res ; 101: 74-85, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26218604

RESUMO

Second generation antipsychotics (SGAs), such as clozapine, olanzapine, risperidone and quetiapine, are among the most effective therapies to stabilize symptoms schizophrenia (SZ) spectrum disorders. In fact, clozapine, olanzapine and risperidone have improved the quality of life of billions SZ patients worldwide. Based on the broad spectrum of efficacy and low risk of extrapyramidal symptoms displayed by SGAs, some regulatory agencies approved the use of SGAs in non-schizophrenic adults, children and adolescents suffering from a range of neuropsychiatric disorders. However, increasing number of reports have shown that SGAs are strongly associated with accelerated weight gain, insulin resistance, diabetes, dyslipidemia, and increased cardiovascular risk. These metabolic alterations can develop in as short as six months after the initiation of pharmacotherapy, which is now a controversial fact in public disclosure. Although the percentage of schizophrenic patients, the main target group of SGAs, is estimated in only 1% of the population, during the past ten years there was an exponential increase in the number of SGAs users, including millions of non-SZ patients. The scientific bases of SGAs metabolic side effects are not yet elucidated, but the evidence shows that the activation of transcriptional factor SRBP1c, the D1/D2 dopamine, GABA2 and 5HT neurotransmitions are implicated in the SGAs cardiovascular toxicity. Polypharmacological interventions are either non- or modestly effective in maintaining low cardiovascular risk in SGAs users. In this review we critically discuss the clinical and molecular evidence on metabolic alterations induced by SGAs, the evidence on the efficacy of classical antidiabetic drugs and the emerging concept of antidiabetic polyphenols as potential coadjutants in SGA-induced metabolic disorders.


Assuntos
Antipsicóticos/efeitos adversos , Síndrome Metabólica/induzido quimicamente , Obesidade/induzido quimicamente , Adolescente , Adulto , Animais , Criança , Humanos , Hipoglicemiantes/uso terapêutico , Metabolismo dos Lipídeos/efeitos dos fármacos , Síndrome Metabólica/metabolismo , Síndrome Metabólica/prevenção & controle , Modelos Biológicos , Obesidade/metabolismo , Obesidade/prevenção & controle , Polifenóis/uso terapêutico , Psicofarmacologia , Aumento de Peso/efeitos dos fármacos
17.
Front Hum Neurosci ; 9: 371, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26190988

RESUMO

Paying attention to visual stimuli is typically accompanied by event-related desynchronizations (ERD) of ongoing alpha (7-14 Hz) activity in visual cortex. The present study used time-frequency based analyses to investigate the role of impaired alpha ERD in visual processing deficits in schizophrenia (Sz). Subjects viewed sinusoidal gratings of high (HSF) and low (LSF) spatial frequency (SF) designed to test functioning of the parvo- vs. magnocellular pathways, respectively. Patients with Sz and healthy controls paid attention selectively to either the LSF or HSF gratings which were presented in random order. Event-related brain potentials (ERPs) were recorded to all stimuli. As in our previous study, it was found that Sz patients were selectively impaired at detecting LSF target stimuli and that ERP amplitudes to LSF stimuli were diminished, both for the early sensory-evoked components and for the attend minus unattend difference component (the Selection Negativity), which is generally regarded as a specific index of feature-selective attention. In the time-frequency domain, the differential ERP deficits to LSF stimuli were echoed in a virtually absent theta-band phase locked response to both unattended and attended LSF stimuli (along with relatively intact theta-band activity for HSF stimuli). In contrast to the theta-band evoked responses which were tightly stimulus locked, stimulus-induced desynchronizations of ongoing alpha activity were not tightly stimulus locked and were apparent only in induced power analyses. Sz patients were significantly impaired in the attention-related modulation of ongoing alpha activity for both HSF and LSF stimuli. These deficits correlated with patients' behavioral deficits in visual information processing as well as with visually based neurocognitive deficits. These findings suggest an additional, pathway-independent, mechanism by which deficits in early visual processing contribute to overall cognitive impairment in Sz.

19.
BMC Psychiatry ; 11: 29, 2011 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-21324141

RESUMO

BACKGROUND: Working memory (WM) tasks usually elicit a P300 ERP component, whose amplitude decreases with increasing WM load. So far, this effect has not been studied in schizophrenics (SZs), a group that is considered to have an aberrant brain connectivity and impairments in WM capacity. The aim of this study was to determine the dependency of the P300 component on WM load in a sample of SZ subjects. METHODS: We recorded 26 subjects (13 SZ patients and their matched controls) with an 80-channel electroencephalogram. Subjects performed an N-back task, a WM paradigm that manipulates the number of items to be stored in memory. RESULTS: In healthy subjects, P300 amplitude was highest in the low WM load condition, and lowest in both the attentional control condition and the high WM load condition. In contrast, SZs evidenced low P300 amplitude in all conditions. A significant between group difference in P300 amplitude was evidenced only at the low WM load condition (1 -back), being smaller in SZs. CONCLUSIONS: SZ subjects display a lower than normal P300 amplitude, which does not vary as a function of memory load. These results are consistent with a general impairment in WM capacity in these patients.


Assuntos
Córtex Cerebral/fisiopatologia , Potenciais Evocados P300/fisiologia , Memória de Curto Prazo/fisiologia , Esquizofrenia/fisiopatologia , Adulto , Análise de Variância , Eletroencefalografia , Feminino , Humanos , Masculino , Testes Neuropsicológicos , Índice de Gravidade de Doença
20.
J Neurochem ; 111(4): 891-900, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19686383

RESUMO

Early models for the etiology of schizophrenia focused on dopamine neurotransmission because of the powerful anti-psychotic action of dopamine antagonists. Nevertheless, recent evidence increasingly supports a primarily glutamatergic dysfunction in this condition, where dopaminergic disbalance is a secondary effect. A current model for the pathophysiology of schizophrenia involves a dysfunctional mechanism by which the NMDA receptor (NMDAR) hypofunction leads to a dysregulation of GABA fast- spiking interneurons, consequently disinhibiting pyramidal glutamatergic output and disturbing the signal-to-noise ratio. This mechanism might explain better than other models some cognitive deficits observed in this disease, as well as the dopaminergic alterations and therapeutic effect of anti-psychotics. Although the modulation of glutamate activity has, in principle, great therapeutic potential, a side effect of NMDAR overactivation is neurotoxicity, which accelerates neuropathological alterations in this illness. We propose that metabotropic glutamate receptors can have a modulatory effect over the NMDAR and regulate excitotoxity mechanisms. Therefore, in our view metabotropic glutamate receptors constitute a highly promising target for future drug treatment in this disease.


Assuntos
Ácido Glutâmico/metabolismo , Receptores de N-Metil-D-Aspartato/fisiologia , Esquizofrenia/metabolismo , Esquizofrenia/fisiopatologia , Animais , Modelos Animais de Doenças , Humanos , Interneurônios/metabolismo , Modelos Neurológicos , Esquizofrenia/terapia , Transdução de Sinais/fisiologia , Ácido gama-Aminobutírico/metabolismo
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