1,721,401 research outputs found
대장 내시경 수련 시뮬레이터의 2 자유도 햅틱장치 개발
No full text학위논문(석사) - 한국과학기술원 : 기계공학전공, 2005.2, [ vi, 54 p. ]This thesis presents a new 2-DOF haptic device for a colonoscopy training simulator. The 2-DOF haptic device includes three parts, a translation motion part, a roll motion part, and folding guides. A wire-driven mechanism is used for translational force reflection. Roll torque is generated by a timing belt mechanism. These two mechanisms implement force and torque reflections large enough for the colonoscopy simulation. The folding guides keep the endoscope tube straight. The folding guides fold and spread like a curtain. This mechanism helps transmit forces and torques from the endoscope tip to the user.
The specifications of 2-DOF haptic device such as continuous and maximum exertable forces and torques; workspace; sensitivity; and inertia in each direction are evaluated. The force bandwidth of the device is also evaluated through frequency response tests. The force bandwidth is suitable for simulation of colonoscopy. The 2-DOF mechanism is decoupled, so that Jacobian matrix has only diagonal elements.
A closed-loop PD controller using a 6-DOF force/torque sensor is designed to reduce the friction and inertial effects. The user``s maneuvering forces are measured in real-time, and compensated for including the effects of coulomb and viscous friction. This provides the users with better transparent sensation of the simulation.
A questionnaire test is conducted to evaluate the 2-DOF haptic device. The result of the questionnaire is analyzed by using a statistical method.한국과학기술원 : 기계공학전공
Association of mental disorders with SARS-CoV-2 infection and severe health outcomes: Nationwide cohort study
No full textCopyright © The Author(s), 2021. Published by Cambridge University Press on behalf of the Royal College of Psychiatrists.Background Epidemiological data on the association between mental disorders and the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) severity are limited. Aims To evaluate the association between mental disorders and the risk of SARS-CoV-2 infection and severe outcomes following COVID-19. Method We performed a cohort study using the Korean COVID-19 patient database based on national health insurance data. Each person with a mental or behavioural disorder (diagnosed during the 6 months prior to their first SARS-CoV-2 test) was matched by age, gender and Charlson Comorbidity Index with up to four people without mental disorders. SARS-CoV-2-positivity risk and the risk of death or severe events (intensive care unit admission, use of mechanical ventilation and acute respiratory distress syndrome) post-infection were calculated using conditional logistic regression analysis. Results Among 230 565 people tested for SARS-CoV-2, 33 653 (14.6%) had mental disorders; 928/33 653 (2.76%) tested SARS-CoV-2 positive and 56/928 (6.03%) died. In multivariable analysis using the matched cohort, there was no association between mental disorders and SARS-CoV-2-positivity risk (odds ratio OR = 0.95; 95% CI 0.87-1.04); however, a higher risk was associated with schizophrenia-related disorders (OR = 1.50; 95% CI 1.14-1.99). Among confirmed COVID-19 patients, the mortality risk was significantly higher in patients with than in those without mental disorders (OR = 1.99, 95% CI 1.15-3.43). Conclusions Mental disorders are likely contributing factors to mortality following COVID-19. Although the infection risk was not higher for people with mental disorders overall, those with schizophrenia-related disorders were more vulnerable to infection.N
The effects of selective serotonin reuptake inhibitors on brain functional networks during goal-directed planning in obsessive-compulsive disorder
No full textWhether brain network connectivity during goal-directed planning in patients with obsessive-compulsive disorder (OCD) is abnormal and restored by treatment with selective serotonin reuptake inhibitors (SSRIs) remains unknown. This study investigated whether the disrupted network connectivity during the Tower of London (ToL) planning task in medication-free OCD patients could be restored by SSRI treatment. Seventeen medication-free OCD patients and 21 matched healthy controls (HCs) underwent functional magnetic resonance imaging (fMRI) while performing the ToL task at baseline and again after 16 weeks of SSRI treatment. Internetwork connectivity was compared across the groups and treatment statuses (pretreatment versus posttreatment). At baseline, compared with the HCs, the OCD patients showed lower internetwork connectivity between the dorsal attention network and the default-mode network during the ToL planning task. After 16 weeks of SSRI treatment, the OCD patients showed improved clinical symptoms accompanied by normalized network connectivity, although their improved behavioral performance in the ToL task did not reach that of the HCs. Our findings support the conceptualization of OCD as a network disease characterized by an imbalance between brain networks during goal-directed planning and suggest that internetwork connectivity may serve as an early biomarker of the effects of SSRIs on goal-directed planning.Y
Neurophysiological Correlate of Emotion Regulation by Cognitive Reappraisal and Its Association With Psychotic Symptoms in Early Psychosis
No full textBackground: Emotion dysregulation is crucial to both poor social functioning and psychotic symptom formation in patients with schizophrenia. The efficient use of emotion regulation strategies, such as cognitive reappraisal, has been less frequently observed in the early phases of psychotic disorder. It is unknown whether neurophysiological responses related to emotion regulation by cognitive reappraisal are altered in early psychosis. Methods: Fifty-four patients with first-episode psychosis (FEP), 34 subjects at clinical high risk (CHR) for psychosis, and 30 healthy controls (HCs) participated in event-related potential recordings during a validated emotion regulation paradigm to measure the effect of cognitive reappraisal on emotion regulation. Late positive potentials (LPPs), which reflect emotional arousal, were compared across the groups and the 3 conditions (negative, cognitive reappraisal, and neutral). The relationship among LPP modulation by cognitive reappraisal and social/role functioning and severity of psychotic symptoms was investigated in the early psychosis group. Results: The FEP and CHR participants showed comparably larger LPP amplitudes in the negative and cognitive reappraisal conditions than in the neutral condition, whereas the HCs presented larger LPPs in the negative condition than in the cognitive reappraisal and neutral conditions. LPP modulation by cognitive reappraisal was negatively correlated with positive symptom severity in the FEP patients and with disorganization severity in the CHR subjects. Conclusions: Inefficient use of cognitive reappraisal may be related to the impaired emotion regulation and psychotic symptoms from the very beginning of psychotic disorder. This study provides the first neurophysiological evidence regarding current concepts of emotion regulation in early psychosis.Y
Relationship between resting-state theta phase-gamma amplitude coupling and neurocognitive functioning in patients with first-episode psychosis
No full textBackground: Although cognitive dysfunction is a core element of schizophrenia, the neurobiological underpinnings of the pathophysiology are not yet sufficiently understood. Because the resting state is crucial for cognitive functioning and electroencephalography (EEG) can reflect instantaneous neural activity, we investigated theta phase-gamma amplitude coupling (TGC) of resting-state EEG and its relationship with cognitive function in patients with first-episode psychosis (FEP) to reveal the neural correlates of cognitive dysfunction. Methods: A total of 59 FEP patients and 50 healthy controls (HCs) underwent resting-state, eyes-closed EEG recordings and performed the Trail Making Test Part A (TMT-A) and Part B (TMT-B) and California Verbal Learning Test (CVLT). TGC from the source signal of the resting-state EEG in default mode network (DMN)-related brain regions was compared between groups. Correlation analyses were performed between TGC and cognitive function test performance in FEP patients. Results: Mean resting-state TGC was larger for the FEP patients than for the HCs. Patients with FEP showed in-creased TGC in the left posterior cingulate cortex, which was correlated with better performance on the TMT-A and TMT-B and on immediate and delayed recall in the MT. Conclusions: These results suggest that patients with FEP show compensatory hyperactivation of resting-state TGC in DMN-related brain regions, which may be related to the reallocation of cognitive resources to prepare for successful cognitive execution. This study not only highlights the neural underpinnings of cognitive dysfunction in FEP patients but also provides useful background to support the development of treatments for cognitive dysfunction in schizophrenia. (C) 2019 Elsevier B.V. All tights reserved.N
Research Trends in Individuals at High Risk for Psychosis: A Bibliometric Analysis
No full textThe study of clinical high risk for psychosis (CHR-P) has progressed rapidly over the last decades and has developed into a significant branch of schizophrenia research. Organizing the information about this rapidly growing subject through bibliometric analysis enables us to gain a better understanding of current research trends and future directions to be pursued. Electronic searches from January 1991 to December 2020 yielded 5,601 studies, and included 1,637 original articles. After processing the data, we were able to determine that this field has grown significantly in a short period of time. It has been confirmed that researchers, institutions, and countries are collaborating closely to conduct research; moreover, these networks are becoming increasingly complex over time. Additionally, there was a shift over time in the focus of the research subject from the prodrome, recognition, prevention, diagnosis to cognition, neuroimaging, neurotransmitters, cannabis, and stigma. We should aim for collaborative studies in which various countries participate, thus covering a wider range of races and cultures than would be covered by only a few countries.N
Functional Connectivity of the Striatum as a Neural Correlate of Symptom Severity in Patient with Obsessive-Compulsive Disorder
No full textObjective It is well established that the cortico-striato-thalamo-cortical (CSTC) circuit is implicated in the pathophysiology of obsessive-compulsive disorder (OCD). However, reports on corticostriatal functional connectivity (FC) in OCD have been inconsistent due to the structural and functional heterogeneity of the striatum. Therefore, in the present study, we investigated corticostriatal FC using a fine 12-seed striatal parcellation to overcome this heterogeneity and discover the neural correlates of symptoms in OCD patients. Methods We recruited 23 OCD patients and 23 healthy controls (HCs). Whole-brain FC based on striatal seeds was examined using resting-state functional magnetic resonance imaging data and compared across OCD patients and HCs. We conducted correlation analysis between FCs of striatal subregions with significant group differences and symptom severity scores on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), Hamilton Rating Scale for Depression, and Hamilton Rating Scale for Anxiety (HAM-A). Results Compared to HCs, patients demonstrated increased FC of the dorsal caudal putamen and ventral rostral putamen (VRP) with several cortical regions, such as the intracalcarine cortex, inferior frontal gyrus, supramarginal/angular gyrus (SMG/AG), and postcentral gyrus (PCG). Furthermore, FC between the VRP and SMG/AG and between the VRP and PCG was negatively correlated with scores on the Y-BOCS compulsive subscale and the HAM-A, respectively. Conclusion These findings suggest that striatal subregions have strengthened FC with extensive cortical regions, which may reflect neural correlates of compulsive and anxious symptoms in OCD patients. These results contribute to an improved understanding of OCD pathophysiology by complementing the current evidence regarding striatal FC.Y
Resting-state functional connectivity of the striatum predicts improvement in negative symptoms and general functioning in patients with first-episode psychosis: A 1-year naturalistic follow-up study
No full textObjective: The persistent disease burden of psychotic disorders often comes from negative symptoms; however, prognostic biomarkers for negative symptoms have not been fully understood. This study investigated whether the altered functional connectivity of the striatum predicts improvement in negative symptoms and functioning after 1 year of usual treatment in patients with first-episode psychosis. Methods: Resting-state functional magnetic imaging was obtained from 40 first-episode psychosis patients and 40 age- and sex-matched healthy control subjects. Whole-brain functional connectivity maps were generated with subdivisions of the striatum as seed regions and compared between first-episode psychosis patients and healthy controls. In 22 patients with first-episode psychosis, follow-up assessments of negative symptom severity and general functional status were conducted after 1 year of usual treatment. Multiple regression analyses were performed to examine factors predictive of symptomatic or functional improvements over the 1-year period. Results: First-episode psychosis patients showed greater functional connectivity between the left dorsal caudate and left primary motor cortex, as well as between the left ventral rostral putamen and right temporal occipital fusiform cortex, than healthy controls. Lower functional connectivity between the right dorsal rostral putamen and anterior cingulate cortex was observed in the first-episode psychosis patients than in healthy controls. In multiple regression analyses, lower functional connectivity of the left dorsal caudate-left primary motor cortex/right dorsal rostral putamen-anterior cingulate cortex predicted improvement in negative symptoms. In addition, lower right dorsal rostral putamen-anterior cingulate cortex functional connectivity predicted improvement in general functioning. Conclusion: These results suggest that altered striatal functional connectivity can be a potent neurobiological marker in the prognosis prediction of first-episode psychosis. Furthermore, altered striatal functional connectivity may provide a potential target in developing treatments for negative symptoms.N
Brain Activation of Patients With Obsessive-Compulsive Disorder During a Mental Rotation Task: A Functional MRI Study
No full textFunctional neuroimaging studies have implicated alterations in frontostriatal and frontoparietal circuits in obsessive-compulsive disorder (OCD) during various tasks. To date, however, brain activation for visuospatial function in conjunction with symptoms in OCD has not been comprehensively evaluated. To elucidate the relationship between neural activity, cognitive function, and obsessive-compulsive symptoms, we investigated regional brain activation during the performance of a visuospatial task in patients with OCD using functional magnetic resonance imaging (fMRI). Seventeen medication-free patients with OCD and 21 age-, sex-, and IQ-matched healthy controls participated in this study. Functional magnetic resonance imaging data were obtained while the subjects performed a mental rotation (MR) task. Brain activation during the task was compared between the two groups using a two-sample t-test. Voxel-wise whole-brain multiple regression analyses were also performed to examine the relationship between obsessive-compulsive symptom severity and neural activity during the task. The two groups did not differ in MR task performance. Both groups also showed similar task-related activation patterns in frontoparietal regions with no significant differences. Activation in the right dorsolateral prefrontal cortex in patients with OCD during the MR task was positively associated with their total Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) scores. This study identified the specific brain areas associated with the interaction between symptom severity and visuospatial cognitive function during an MR task in medication-free patients with OCD. These findings may serve as potential neuromodulation targets for OCD treatment.Y
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