24 results on '"Nak-Young Kim"'
Search Results
2. Impact of transdermal trigeminal electrical neuromodulation on subjective and objective sleep parameters in patients with insomnia: a pilot study
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Nak-Young Kim, Yoo Hyun Um, Sheng-Min Wang, Hyun Kook Lim, and Dong Woo Kang
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Trigeminal nerve ,medicine.medical_specialty ,Sleepiness ,Neurology ,medicine.diagnostic_test ,business.industry ,Polysomnography ,Epworth Sleepiness Scale ,Pilot Projects ,Neuromodulation (medicine) ,Pittsburgh Sleep Quality Index ,Otorhinolaryngology ,Sleep Initiation and Maintenance Disorders ,mental disorders ,medicine ,Insomnia ,Physical therapy ,Humans ,Neurology (clinical) ,medicine.symptom ,Sleep ,business - Abstract
Transcutaneous trigeminal electrical neuromodulation (TTEN) is a new treatment modality that has a potential to improve sleep through the suppression of noradrenergic activity. This study aimed to explore the changes of subjective and objective sleep parameters after 4-weeks of daily session of transcutaneous trigeminal electrical neuromodulation in a group of patients with insomnia. In a group of patients with insomnia, TTEN targeting the ophthalmic division of the trigeminal nerve was utilized to test the effects of transcutaneous trigeminal electrical neuromodulation. Patients went through daily 20-min sessions of TTEN for 4 weeks. Polysomnography parameters, Pittsburgh sleep quality index, insomnia severity index, and Epworth sleepiness scale were obtained pre- and post-intervention. Changes in these parameters were compared and analyzed. Among 13 patients with insomnia there was a statistically significant reduction in Pittsburgh sleep quality index, insomnia severity index, and Epworth sleepiness scale scores after 4-week daily sessions of TTEN. There were no differences in polysomnography parameters pre- and post-intervention. This is the first study to demonstrate the effects of TTEN in a group of insomnia patients. TTEN may improve subjective parameters in patients with insomnia. Further replication studies are needed to support this finding. The data presented in the study are from a study exploring the effect of TTEN on insomnia ( www.clinicaltrials.gov , registration number: NCT04838067, date of registration: April 8, 2021, “retrospectively registered”)
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- 2021
3. Default mode network dissociation linking cerebral beta amyloid retention and depression in cognitively normal older adults
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Dong Woo Kang, Nak-Young Kim, Hyun Kook Lim, Sheng-Min Wang, Yoo Hyun Um, Chang-Uk Lee, and Hae-Ran Na
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Adult ,medicine.medical_specialty ,Dissociation (neuropsychology) ,Amyloid ,Neuropsychological Tests ,Article ,03 medical and health sciences ,0302 clinical medicine ,Internal medicine ,medicine ,Humans ,Beta (finance) ,Default mode network ,Depression (differential diagnoses) ,Pharmacology ,Brain Mapping ,Amyloid beta-Peptides ,medicine.diagnostic_test ,Depression ,business.industry ,Functional connectivity ,Brain ,Default Mode Network ,Magnetic Resonance Imaging ,Aβ deposition ,030227 psychiatry ,Psychiatry and Mental health ,Endocrinology ,business ,Functional magnetic resonance imaging ,human activities ,030217 neurology & neurosurgery - Abstract
Cerebral beta amyloid (Aβ) deposition and late-life depression (LLD) are known to be associated with the trajectory of Alzheimer’s disease (AD). However, their neurobiological link is not clear. Previous studies showed aberrant functional connectivity (FC) changes in the default mode network (DMN) in early Aβ deposition and LLD, but its mediating role has not been elucidated. This study was performed to investigate the distinctive association pattern of DMN FC linking LLD and Aβ retention in cognitively normal older adults. A total of 235 cognitively normal older adults with (n = 118) and without depression (n = 117) underwent resting-state functional magnetic resonance imaging and (18)F-flutemetamol positron emission tomography to investigate the associations between Aβ burden, depression, and DMN FC. Independent component analysis showed increased anterior DMN FC and decreased posterior DMN FC in the depression group compared with the no depression group. Global cerebral Aβ retention was positively correlated with anterior and negatively correlated with posterior DMN FC. Anterior DMN FC was positively correlated with severity of depression, whereas posterior DMN FC was negatively correlated with cognitive function. In addition, the effects of global cerebral Aβ retention on severity of depression were mediated by subgenual anterior cingulate FC. Our results of anterior and posterior DMN FC dissociation pattern may be pivotal in linking cerebral Aβ pathology and LLD in the course of AD progression. Further longitudinal studies are needed to confirm the causal relationships between cerebral Aβ retention and LLD.
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- 2021
4. Association between Dementia and Clinical Outcome after COVID-19: A Nationwide Cohort Study with Propensity Score Matched Control in South Korea
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Hyun Kook Lim, Sheng-Min Wang, See Hyun Park, Sung-Soo Park, Yoo Hyun Um, Dong Woo Kang, Seunghoon Han, Nak-Young Kim, and Hae-Ran Na
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medicine.medical_specialty ,Coronavirus disease 2019 (COVID-19) ,03 medical and health sciences ,0302 clinical medicine ,Internal medicine ,mental disorders ,Risk of mortality ,Medicine ,Dementia ,030212 general & internal medicine ,Mortality ,Biological Psychiatry ,business.industry ,SARS-CoV-2 ,Mortality rate ,COVID-19 ,Odds ratio ,medicine.disease ,Psychiatry and Mental health ,Propensity score matching ,Cohort ,Original Article ,business ,030217 neurology & neurosurgery ,Cohort study - Abstract
Despite a high prevalence of dementia in older adults hospitalized with severe acute respiratory syndrome coronavirus 2 infection (COVID-19), research investigating association between preexisting diagnoses of dementia and prognosis of COVID-19 is scarce. We explored a nationwide cohort with a total of 2,800 subjects older than 50 years who were diagnosed with COVID-19 between January and April 2020. Among them, 223 patients had underlying dementia (dementia group). We matched 1:1 for each dementia-non-dementia group pair yielding 223 patients without dementia (no dementia group) using propensity score matching. The primary outcome measure was group difference in mortality after COVID-19. Mortality rate after COVID-19 were significantly higher in dementia group than in no dementia group (33.6% vs. 20.2%, p=0.002). In addition, dementia group had higher proportion of patients requiring invasive ventilatory support than no dementia group (34.1% vs. 22.0%, p=0.006). Multivariable analysis showed that dementia group had a higher risk of mortality than no dementia group (odds ratio=3.05, p
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- 2021
5. Rapid Onset of Intranasal Esketamine in Patients with Treatment Resistant Depression and Major Depression with Suicide Ideation: A Meta-Analysis
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Hyun Kook Lim, Hae-Ran Na, Won-Myong Bahk, Nak-Young Kim, Sheng-Min Wang, Chi-Un Pae, and Young Sup Woo
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medicine.medical_specialty ,Nausea ,Esketamine ,Placebo ,Treatment resistant depression ,03 medical and health sciences ,Behavioral Neuroscience ,0302 clinical medicine ,Internal medicine ,Medicine ,Pharmacology (medical) ,Adverse effect ,Depression (differential diagnoses) ,Depression ,business.industry ,medicine.disease ,Meta-analysis ,030227 psychiatry ,Dysgeusia ,Suicide ,Psychiatry and Mental health ,Major depressive disorder ,Original Article ,medicine.symptom ,business ,Treatment-resistant depression ,030217 neurology & neurosurgery ,medicine.drug - Abstract
Objective We performed a meta-analysis of randomized double-blinded placebo controlled trials (DB-RCTs) to investigate efficacy and safety of intranasal esketamine in treating major depressive disorder (MDD) including treatment resistant depression (TRD) and major depression with suicide ideation (MDSI). Methods Mean change in total scores on Montgomery-Åsberg Depression Rating Scale (MADRS) from baseline to different time-points were our primary outcome measure. Secondary efficacy measures included rate of remission of depression and resolution of suicidality. Results Eight DB-RCTs (seven published and one un-published) covering 1,488 patients with MDD were included. Esketamine more significantly improved MADRS total scores than placebo starting from 2−4 hours after the first administration (standardized mean difference, −0.41 [95% CI, −0.58 to −0.25], p < 0.00001), and this superiority maintained until end of double-blinded period (28 days). Sub-group analysis showed that superior antidepressant effects of esketamine over placebo in TRD and MDSI was observed from 2−4 hours, which was maintained until 28 days. Resolution of suicide in MDSI was also greater for esketamine than for placebo at 2−4 hours (OR of 2.04, 95% CIs, 1.37 to 3.05, p = 0.0005), but two groups did not statistically differ at 24 hours and day 28. Total adverse events (AEs), and other common AEs including dissociation, blood pressure increment, nausea, vertigo, dysgeusia, dizziness, and somnolence were more frequent in esketamine than in placebo group. Conclusion Esketamine showed rapid antidepressant effects in patients with MDD, including TRD and MDSI. The study also suggested that esketamine might be associated with rapid anti-suicidal effects for patients with MDSI.
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- 2021
6. Pre-transplant Dementia is Associated with Poor Survival After Hematopoietic Stem Cell Transplantation: A Nationwide Cohort Study with Propensity Score Matched Control
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Hae-Ran Na, Nak-Young Kim, Sheng-Min Wang, See Hyun Park, Jong Wook Lee, Dong Woo Kang, Sung-Soo Park, Seunghoon Han, Young-Yi Bae, and Hyun Kook Lim
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medicine.medical_specialty ,Multivariate analysis ,Survival ,medicine.medical_treatment ,Hematopoietic stem cell transplantation ,03 medical and health sciences ,Behavioral Neuroscience ,0302 clinical medicine ,Internal medicine ,mental disorders ,medicine ,Risk of mortality ,Dementia ,Pharmacology (medical) ,business.industry ,medicine.disease ,Confidence interval ,Transplantation ,Treatment ,Psychiatry and Mental health ,surgical procedures, operative ,030220 oncology & carcinogenesis ,Propensity score matching ,Original Article ,business ,030217 neurology & neurosurgery ,Cohort study - Abstract
Objective No previous study examined impact of dementia in the outcome of allogeneic hematopoietic stem cell transplantation (HSCT). We aimed to investigate overall survival (OS) of patients with dementia after receiving HSCT. Methods Among 8,230 patients who underwent HSCT between 2002 and 2018, 5,533 patients younger than 50 years were first excluded. Remaining patients were divided into those who were and were not diagnosed with dementia before HSCT (dementia group: n = 31; no dementia: n = 2,666). Thereafter, among 2,666 participants without dementia, 93 patients were selected via propensity-matched score as non-dementia group. Patients were followed from the day they received HSCT to the occurrence of death or the last follow-up day (December 31, 2018), whichever came first. Results With median follow-up of 621 days for dementia group and 654 days for non-dementia group, 2 year-OS of dementia group was lower than that of non-dementia group (53.3% [95% confidence interval, 95% CI, 59.0-80.2%] vs. 68.8% [95% CI, 38.0-68.2%], p = 0.076). In multivariate analysis, dementia had significant impacts on OS (hazard risk = 2.539, 95% CI, 1.166-4.771, p = 0.017). Conclusion Our results indicated that patients diagnosed with dementia before HSCT have 2.539 times higher risk of mortality after transplantation than those not having dementia. With number of elderly needing HSCT is increasing, further work to establish treatment guidelines for the management of HSCT in people with dementia is needed.
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- 2021
7. Pre-transplant depression decreased overall survival of patients receiving allogeneic hematopoietic stem cell transplantation: a nationwide cohort study
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Dong Woo Kang, Seunghoon Han, Sheng-Min Wang, Hyun Kook Lim, Si-Hyun Park, Nak-Young Kim, Hae-Ran Na, Sung-Soo Park, and Jong Wook Lee
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0301 basic medicine ,Male ,medicine.medical_specialty ,Patients ,lcsh:Medicine ,Article ,03 medical and health sciences ,0302 clinical medicine ,Internal medicine ,Republic of Korea ,medicine ,Humans ,Transplantation, Homologous ,Signs and symptoms ,lcsh:Science ,Survival rate ,Depression (differential diagnoses) ,Retrospective Studies ,Multidisciplinary ,business.industry ,Depression ,Hazard ratio ,lcsh:R ,Hematopoietic Stem Cell Transplantation ,Retrospective cohort study ,Middle Aged ,medicine.disease ,Anxiety Disorders ,Transplantation ,Survival Rate ,030104 developmental biology ,surgical procedures, operative ,Neurology ,Oncology ,Risk factors ,030220 oncology & carcinogenesis ,Anxiety ,Female ,lcsh:Q ,medicine.symptom ,business ,Anxiety disorder ,Cohort study - Abstract
Studies investigating association of depression with overall survival (OS) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) yielded conflicting results. A nationwide cohort study, which included all adult patients [n = 7,170; depression group, 13.3% (N = 956); non-depression group, 86.7% (N = 6,214)] who received allo-HSCT from 2002 to 2018 in South Korea, analyzed risk of pre-transplant depression in OS of allo-HSCT. Subjects were followed from the day they received allo-HSCT, to occurrence of death, or last follow-up day (December 31, 2018). Median age at allo-HSCT for depression and non-depression groups were 50 and 45 (p p p p = 0.04), and to having both depression and anxiety disorder (aHR = 1.202, CI: 1.038–1.393, p = 0.014) groups. Pre-transplant anxiety (anxiety only) did not have significant influence in OS. Additional medical and psychiatric care might be necessary in patients who experienced depression, especially with anxiety, before allo-HSCT.
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- 2020
8. Differential Impact of Cigarette Smoking on Fracture Risks in Subjective Cognitive Decline and Dementia: A Nationwide Longitudinal Study
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Chang-Uk Lee, Yoo Hyun Um, Hae-Ran Na, Sheng-Min Wang, Kyungdo Han, Hyun Kook Lim, Nak-Young Kim, and Dong Woo Kang
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medicine.medical_specialty ,Longitudinal study ,medicine.medical_treatment ,Population ,Smoking cessation ,03 medical and health sciences ,Cognition ,0302 clinical medicine ,Internal medicine ,Medicine ,Dementia ,030212 general & internal medicine ,Cognitive decline ,education ,Biological Psychiatry ,education.field_of_study ,business.industry ,Smoking ,Hazard ratio ,Confounding ,medicine.disease ,Psychiatry and Mental health ,Original Article ,business ,Fractures ,030217 neurology & neurosurgery ,Cohort study - Abstract
Objective We aimed to explore the differential impact of cigarette smoking on fracture risks in SCD and dementia.Methods A nationwide population-based cohort study design was used. Out of all the people aged 66 (n=1,555,103) who went through the National Screening Program from 2009–2014, 968,240 participants with eligible data were included in the study. Time-to-event was calculated as the duration between the NSPTA and fracture incidence. Cox proportional-hazard regression analyses were conducted to evaluate the risk of fractures.Results Increased risk of all [adjusted hazard ratio (aHR)=1.184; 95% confidence interval (CI)=1.184, 1.093–1.283], hip (aHR=1.518; 95% CI=1.168–4.972), vertebral (aHR=1.235; 95% CI=1.101–1.386) fractures were increased in current smokers with more than 20 or more pack years (≥20 py) of SCD group, after adjusting for all relevant confounding factors. In dementia group, however, current smokers ≥20 py were at reduced risk of hip fractures (aHR=0.249; 95% CI=0.089–0.97).Conclusion There was a disparate influence of cigarette smoking on the fracture risks in SCD and dementia group. Further studies are warranted to explicate this phenomenon, and personalized preventive measures according to one’s cognitive status are imperative, since risk factors of fractures can exert disparate influence on patients at different stage of cognitive trajectory.
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- 2020
9. Distinctive Association of the Functional Connectivity of the Posterior Cingulate Cortex on Memory Performances in Early and Late Amnestic Mild Cognitive Impairment Patients
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Chang-Uk Lee, Yoo Hyun Um, Hyun Kook Lim, Hae-Ran Na, Dong Woo Kang, Nak-Young Kim, and Sheng-Min Wang
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early mild cognitive impairment ,Aging ,medicine.medical_specialty ,Cerebellum ,Cognitive Neuroscience ,Neurosciences. Biological psychiatry. Neuropsychiatry ,Audiology ,behavioral disciplines and activities ,late mild cognitive impairment ,03 medical and health sciences ,Superior temporal gyrus ,0302 clinical medicine ,Cortex (anatomy) ,mental disorders ,medicine ,posterior cingulate cortex ,Association (psychology) ,memory performance ,030304 developmental biology ,Original Research ,0303 health sciences ,business.industry ,Neurodegeneration ,functional connectivity ,Neuropsychology ,Medial frontal gyrus ,medicine.disease ,medicine.anatomical_structure ,Posterior cingulate ,business ,030217 neurology & neurosurgery ,RC321-571 ,Neuroscience - Abstract
BackgroundAttempts have been made to explore the biological basis of neurodegeneration in the amnestic mild cognitive impairment (MCI) stage, subdivided by memory performance. However, few studies have evaluated the differential impact of functional connectivity (FC) on memory performances in early- and late-MCI patients.ObjectiveThis study aims to explore the difference in FC of the posterior cingulate cortex (PCC) among healthy controls (HC) (n = 37), early-MCI patients (n = 30), and late-MCI patients (n = 35) and to evaluate a group-memory performance interaction against the FC of PCC.MethodsThe subjects underwent resting-state functional MRI scanning and a battery of neuropsychological tests.ResultsA significant difference among the three groups was found in FC between the PCC (seed region) and bilateral crus cerebellum, right superior medial frontal gyrus, superior temporal gyrus, and left middle cingulate gyrus (Monte Carlo simulation-corrected p < 0.01; cluster p < 0.05). Additionally, the early-MCI patients displayed higher FC values than the HC and late-MCI patients in the right superior medial frontal gyrus, cerebellum crus 1, and left cerebellum crus 2 (Bonferroni-corrected p < 0.05). Furthermore, there was a significant group-memory performance interaction (HC vs. early MCI vs. late MCI) for the FC between PCC and bilateral crus cerebellum, right superior medial frontal gyrus, superior temporal gyrus, and left middle cingulate gyrus (Bonferroni-corrected p < 0.05).ConclusionThese findings contribute to the biological implications of early- and late-MCI stages, categorized by evaluating the impairment of memory performance. Additionally, comprehensively analyzing the structural differences in the subdivided amnestic MCI (aMCI) stages could deepen our understanding of these biological meanings.
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- 2021
10. A Comparative Study on the Predictive Value of Different Resting-State Functional Magnetic Resonance Imaging Parameters in Preclinical Alzheimer's Disease
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Young Sup Woo, Dong Woo Kang, Hyun Kook Lim, Sheng-Min Wang, Hae-Ran Na, Nak-Young Kim, Yoo Hyun Um, Won-Myong Bahk, and Chang-Uk Lee
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medicine.medical_specialty ,Brain activity and meditation ,diagnosis ,RC435-571 ,03 medical and health sciences ,0302 clinical medicine ,Internal medicine ,medicine ,magnetic resonance imaging ,030304 developmental biology ,Original Research ,Psychiatry ,0303 health sciences ,function ,Receiver operating characteristic ,medicine.diagnostic_test ,business.industry ,Curve analysis ,amyloid ,Magnetic resonance imaging ,Alzheimer's disease ,Predictive value ,Resting state functional magnetic resonance imaging ,Psychiatry and Mental health ,Sample size determination ,Cardiology ,Functional magnetic resonance imaging ,business ,030217 neurology & neurosurgery - Abstract
Objective: Diverse resting-state functional magnetic resonance imaging (rs-fMRI) studies showed that rs-fMRI might be able to reflect the earliest detrimental effect of cerebral beta-amyloid (Aβ) pathology. However, no previous studies specifically compared the predictive value of different rs-fMRI parameters in preclinical AD.Methods: A total of 106 cognitively normal adults (Aβ+ group = 66 and Aβ− group = 40) were included. Three different rs-fMRI parameter maps including functional connectivity (FC), fractional amplitude of low-frequency fluctuations (fALFF), and regional homogeneity (ReHo) were calculated. Receiver operating characteristic (ROC) curve analyses were utilized to compare classification performance of the three rs-fMRI parameters.Results: FC maps showed the best classifying performance in ROC curve analysis (AUC, 0.915, p < 0.001). Good but weaker performance was achieved by using ReHo maps (AUC, 0.836, p < 0.001) and fALFF maps (AUC, 0.804, p < 0.001). The brain regions showing the greatest discriminative power included the left angular gyrus for FC, left anterior cingulate for ReHo, and left middle frontal gyrus for fALFF. However, among the three measurements, ROI-based FC was the only measure showing group difference in voxel-wise analysis.Conclusion: Our results strengthen the idea that rs-fMRI might be sensitive to earlier changes in spontaneous brain activity and FC in response to cerebral Aβ retention. However, further longitudinal studies with larger sample sizes are needed to confirm their utility in predicting the risk of AD.
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- 2021
11. Differential Impact of Education on Gray Matter Volume According to Sex in Cognitively Normal Older Adults: Whole Brain Surface-Based Morphometry
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Hyun Kook Lim, Dong Woo Kang, Chang-Uk Lee, Nak-Young Kim, Hae-Ran Na, and Sheng-Min Wang
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medicine.medical_specialty ,genetic structures ,lcsh:RC435-571 ,Brain surface ,Audiology ,Affect (psychology) ,Gray (unit) ,03 medical and health sciences ,0302 clinical medicine ,lcsh:Psychiatry ,Medicine ,sex ,gray matter volume ,030304 developmental biology ,Differential impact ,Cognitive reserve ,Original Research ,Psychiatry ,0303 health sciences ,education ,business.industry ,cognitively normal older adults ,Regression analysis ,Cognition ,surface-based morphometry ,Psychiatry and Mental health ,business ,030217 neurology & neurosurgery ,Volume (compression) - Abstract
Background:The effect of educational status on brain structural measurements depends on demographic and clinical factors in cognitively healthy older adults.Objectives:The current study aimed to evaluate the impact of interaction between years of education and sex on gray matter volume and to investigate whether cortical volume has a differential impact on cognitive function according to sex.Methods:One hundred twenty-one subjects between 60 and 85 years old were included in this study. Gray matter volume was evaluated by whole brain surface-based morphometry. Multiple regression analysis was used to analyze the effects of sex-cortical volume interactions on cognitive functions.Results:There was a significant interaction between years of education and sex on the cortical volume of the left inferior temporal gyrus after adjusting for age, APOE ε4 allele prevalence, and total intracranial volume. In addition, we found a significant impact of the interaction between adjusted left inferior temporal volume and sex on CERAD-K total scores.Conclusion:These findings have significant implications for the understanding of how sex could affect the role of cognitive reserve for cortical atrophy in cognitively intact older adults.
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- 2021
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12. Late-life depression, subjective cognitive decline, and their additive risk in incidence of dementia: A nationwide longitudinal study
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Hyun Kook Lim, Yoo Hyun Um, Sheng-Min Wang, Nak-Young Kim, Chang-Uk Lee, Hae-Ran Na, Dong Woo Kang, and Kyungdo Han
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Health Screening ,Longitudinal study ,Epidemiology ,Alzheimer's Disease ,Geriatric Depression ,Medical Conditions ,Cognition ,Learning and Memory ,0302 clinical medicine ,Medicine and Health Sciences ,Public and Occupational Health ,Longitudinal Studies ,030212 general & internal medicine ,Cognitive decline ,Depression (differential diagnoses) ,Aged, 80 and over ,Cognitive Impairment ,education.field_of_study ,Multidisciplinary ,Depression ,Cognitive Neurology ,Incidence ,Hazard ratio ,Neurodegenerative Diseases ,Middle Aged ,Late life depression ,Neurology ,Medicine ,Research Article ,Cohort study ,medicine.medical_specialty ,Cognitive Neuroscience ,Science ,Geriatric Psychiatry ,Population ,03 medical and health sciences ,Memory ,Internal medicine ,Mental Health and Psychiatry ,medicine ,Humans ,Dementia ,Cognitive Dysfunction ,education ,Aged ,Mood Disorders ,business.industry ,Biology and Life Sciences ,medicine.disease ,Geriatrics ,Medical Risk Factors ,Cognitive Science ,business ,030217 neurology & neurosurgery ,Neuroscience - Abstract
Objective Late-life depression and subjective cognitive decline (SCD) are significant risk factors for dementia. However, studies with a large sample size are needed to clarify their independent and combined risks for subsequent dementia. Methods This nationwide population-based cohort study included all individuals aged 66 years who participated in the National Screening Program between 2009 and 2013 (N = 939,099). Subjects were followed from the day they underwent screening to the diagnosis of dementia, death, or the last follow-up day (December 31, 2017). Results Depressive symptom presentation, recent depressive disorder, and SCD independently increased dementia incidence with adjusted hazard ratio (aHR) of 1.286 (95% CI:1.255–1.318), 1.697 (95% CI:1.621–1.776), and 1.748 (95% CI: 689–1.808) respectively. Subjects having both SCD and depression had a higher risk (aHR = 2.466, 95% CI:2.383–2.551) of dementia than having depression (aHR = 1.402, 95% CI:1.364–1.441) or SCD (aHR = 1.748, 95% CI:1.689–1.808) alone. Conclusions Depressive symptoms, depressive disorder, and SCD are independent risk factors for dementia. Co-occurring depression and SCD have an additive effect on the risk of dementia; thus, early intervention and close follow up are necessary for patients with co-occurring SCD and depression.
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- 2021
13. Split-Attention U-Net: A Fully Convolutional Network for Robust Multi-Label Segmentation from Brain MRI
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Dong Woo Kang, Donghyeon Kim, ZunHyan Rieu, Sheng-Min Wang, Min Kyoung Lee, Jung Hyun Yong, Minho Lee, Regina E. Y. Kim, Hyun Kook Lim, Hyun Gi Kim, Se Won Oh, Nak-Young Kim, and Jee-Young Kim
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Computer science ,Normalization (image processing) ,Convolutional neural network ,Article ,lcsh:RC321-571 ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Neuroimaging ,Robustness (computer science) ,Brain segmentation ,Segmentation ,Pyramid (image processing) ,split-attention block ,lcsh:Neurosciences. Biological psychiatry. Neuropsychiatry ,business.industry ,General Neuroscience ,Deep learning ,multi-label brain segmentation ,deep learning ,Pattern recognition ,SAU-Net ,Artificial intelligence ,business ,fine-tuning ,030217 neurology & neurosurgery - Abstract
Multi-label brain segmentation from brain magnetic resonance imaging (MRI) provides valuable structural information for most neurological analyses. Due to the complexity of the brain segmentation algorithm, it could delay the delivery of neuroimaging findings. Therefore, we introduce Split-Attention U-Net (SAU-Net), a convolutional neural network with skip pathways and a split-attention module that segments brain MRI scans. The proposed architecture employs split-attention blocks, skip pathways with pyramid levels, and evolving normalization layers. For efficient training, we performed pre-training and fine-tuning with the original and manually modified FreeSurfer labels, respectively. This learning strategy enables involvement of heterogeneous neuroimaging data in the training without the need for many manual annotations. Using nine evaluation datasets, we demonstrated that SAU-Net achieved better segmentation accuracy with better reliability that surpasses those of state-of-the-art methods. We believe that SAU-Net has excellent potential due to its robustness to neuroanatomical variability that would enable almost instantaneous access to accurate neuroimaging biomarkers and its swift processing runtime compared to other methods investigated.
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- 2020
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14. Differential Risk of Incident Fractures Depending on Intensity and Frequency of Physical Activity According to Cognitive Status: A Nationwide Longitudinal Study
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Yoo Hyun Um, Hae-Ran Na, Sheng-Min Wang, Chang-Uk Lee, Kyungdo Han, Dong Woo Kang, Nak-Young Kim, and Hyun Kook Lim
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medicine.medical_specialty ,Longitudinal study ,Physical activity ,physical activity ,030209 endocrinology & metabolism ,03 medical and health sciences ,0302 clinical medicine ,Medicine ,Dementia ,030212 general & internal medicine ,Cognitive decline ,older adults ,Original Research ,lcsh:R5-920 ,business.industry ,Hazard ratio ,Cognition ,General Medicine ,medicine.disease ,Intensity (physics) ,fracture ,Physical therapy ,subjective cognitive decline ,lcsh:Medicine (General) ,business ,dementia ,Cohort study - Abstract
Background: Previous studies have demonstrated an increased risk of fractures in subjects with various degrees of cognitive impairments. Recently, there has been growing recognition of the vital effect of physical activity (PA) on delay and prevention of fractures in older adults.Objectives: This study aimed to evaluate the optimal intensity and frequency of PA needed to prevent fractures in cognitively preserved older adults (CP), participants with subjective cognitive decline (SCD), and dementia patients using a large-scale nationwide cohort study.Methods: Data from a nationwide health screening program for individuals at the transitional age of 66 years were used in this study. A total of 968,240 subjects was enrolled, followed from 2007 to 2014, and classified as CP (n = 759,874), SCD (n = 195,365), or dementia group (n = 13,001). Adjusted hazard ratios (aHRs) by demographic and known risk factors for fractures were evaluated to identify the impact of various frequency and intensity PA on the occurrence of hip, vertebral, and limb fractures.Results: In CP participants, the most noticeable reduction of hip and vertebral fracture risk was shown in those performing vigorous-intensity PA at least three times per week. In the SCD group, the risk decrement in hip and vertebral fractures was most prominent in subjects who performed multiple-intensity PAs at least three times a week regardless of intensity. In the dementia group, only high-frequency walking and high-frequency & multiple-intensity PA decreased the risk of hip fractures compared with absence of PA.Conclusion: These findings suggest a role for various PA intensity and frequency levels to prevent hip and vertebral fractures according to cognitive status. Further study is needed to validate the effects of PA intensity and frequency proposed in this study on fractures according to cognitive status.
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- 2020
15. Differences in cortical structure between cognitively normal East Asian and Caucasian older adults: a surface-based morphometry study
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Dong Woo Kang, Chang-Uk Lee, Donghyeon Kim, Nak Young Kim, Sheng-Min Wang, Hae-Ran Na, Sonya Youngju Park, Hyun Kook Lim, and Seong-Jin Son
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Male ,medicine.medical_specialty ,Brain Structure and Function ,Audiology ,050105 experimental psychology ,Article ,White People ,Lingual gyrus ,03 medical and health sciences ,0302 clinical medicine ,Cognition ,Asian People ,Inferior temporal gyrus ,Cortex (anatomy) ,medicine ,Humans ,0501 psychology and cognitive sciences ,Aged ,Temporal cortex ,Aged, 80 and over ,Cerebral Cortex ,Multidisciplinary ,business.industry ,Postcentral gyrus ,Cognitive ageing ,05 social sciences ,Brain morphometry ,Precentral gyrus ,Brain ,Middle Aged ,Magnetic Resonance Imaging ,medicine.anatomical_structure ,Female ,business ,030217 neurology & neurosurgery - Abstract
There is a growing literature on the impact of ethnicity on brain structure and function. Despite the regional heterogeneity in age-related changes and non-uniformity across brain morphometry measurements in the aging process, paucity of studies investigated the difference in cortical anatomy between the East Asian and Caucasian older adults. The present study aimed to compare cortical anatomy measurements, including cortical thickness, volume and surface area, between cognitively normal East Asian (n = 171) and Caucasian (n = 178) older adults, using surface-based morphometry and vertex-wise group analysis of high-dimensional structural magnetic resonance imaging (MRI) data. The East Asian group showed greater cortical thickness and larger cortical volume in the right superior temporal gyrus, postcentral gyrus, bilateral inferior temporal gyrus, and inferior parietal cortex. The Caucasian group showed thicker and larger cortex in the left transverse temporal cortex, lingual gyrus, right lateral occipital cortex, and precentral gyrus. Additionally, the difference in surface area was discordant with that in cortical thickness. Differences in brain structure between the East Asian and Caucasian might reflect differences in language and information processing, but further studies using standardized methods for assessing racial characteristics are needed. The research results represent a further step towards developing a comprehensive understanding of differences in brain structure between ethnicities of older adults, and this would enrich clinical research on aging and neurodegenerative diseases.
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- 2020
16. Long-Term Ambient Air Pollution Exposures and Brain Imaging Markers in Korean Adults: The Environmental Pollution-Induced Neurological EFfects (EPINEF) Study
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Hwasun Seo, Sun Young Kim, Seong Kyung Cho, Young Noh, Changsoo Kim, Sung Soo Oh, Dae Seock Shin, Jungwoo Sohn, Seongho Seo, Woojin Kim, Seung Koo Lee, Nak-Young Kim, Sang Baek Koh, Hee Jin Kim, Jung Il Lee, Sang Won Seo, Jaelim Cho, Juhwan Noh, Gayoung Seo, and Ho Hyun Kim
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Adult ,Male ,Health, Toxicology and Mutagenesis ,Nitrogen Dioxide ,Neuroimaging ,Environmental pollution ,010501 environmental sciences ,01 natural sciences ,Cortical volume ,03 medical and health sciences ,0302 clinical medicine ,Air Pollution ,Environmental health ,Republic of Korea ,Humans ,Medicine ,030212 general & internal medicine ,0105 earth and related environmental sciences ,Air Pollutants ,Ambient air pollution ,business.industry ,Research ,Public Health, Environmental and Occupational Health ,Brain ,Environmental Exposure ,Middle Aged ,Neurological effects ,Female ,Particulate Matter ,business ,Biomarkers - Abstract
Background: Only a limited number of neuroimaging studies have explored the effects of ambient air pollution in adults. The prior studies have investigated only cortical volume, and they have reported mixed findings, particularly for gray matter. Furthermore, the association between nitrogen dioxide (NO2) and neuroimaging markers has been little studied in adults. Objectives: We investigated the association between long-term exposure to air pollutants (NO2, particulate matter (PM) with aerodynamic diameters of ≤10μm (PM10) and ≤2.5μm (PM2.5), and neuroimaging markers. Methods: The study included 427 men and 530 women dwelling in four cities in the Republic of Korea. Long-term concentrations of PM10, NO2, and PM2.5 at residential addresses were estimated. Neuroimaging markers (cortical thickness and subcortical volume) were obtained from brain magnetic resonance images. A generalized linear model was used, adjusting for potential confounders. Results: A 10-μg/m3 increase in PM10 was associated with reduced thicknesses in the frontal [–0.02mm (95% CI: –0.03, –0.01)] and temporal lobes [–0.06mm (95% CI: –0.07, –0.04)]. A 10-μg/m3 increase in PM2.5 was associated with a thinner temporal cortex [–0.18mm (95% CI: –0.27, –0.08)]. A 10-ppb increase in NO2 was associated with reduced thicknesses in the global [–0.01mm (95% CI: –0.01, 0.00)], frontal [–0.02mm (95% CI: –0.03, –0.01)], parietal [–0.02mm (95% CI: –0.03, –0.01)], temporal [–0.04mm (95% CI: –0.05, –0.03)], and insular lobes [–0.01mm (95% CI: –0.02, 0.00)]. The air pollutants were also associated with increased thicknesses in the occipital and cingulate lobes. Subcortical structures associated with the air pollutants included the thalamus, caudate, pallidum, hippocampus, amygdala, and nucleus accumbens. Discussion: The findings suggest that long-term exposure to high ambient air pollution may lead to cortical thinning and reduced subcortical volume in adults. https://doi.org/10.1289/EHP7133
- Published
- 2020
17. Agomelatine for the Treatment of Generalized Anxiety Disorder: A Meta-Analysis
- Author
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Sheng Min Wang, Hyun Kook Lim, Won-Myong Bahk, Hae-Ran Na, Nak-Young Kim, and Young Sup Woo
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medicine.medical_specialty ,Generalized anxiety disorder ,Hamilton Anxiety Rating Scale ,Placebo ,03 medical and health sciences ,Behavioral Neuroscience ,0302 clinical medicine ,Internal medicine ,medicine ,Agomelatine ,Pharmacology (medical) ,030212 general & internal medicine ,business.industry ,medicine.disease ,Clinical trial ,Treatment ,Psychiatry and Mental health ,Meta-analysis ,Strictly standardized mean difference ,Anxiety disorder ,Original Article ,Liver function ,business ,030217 neurology & neurosurgery ,medicine.drug - Abstract
Objective Despite multiple drugs available, a large proportion of patients with generalized anxiety disorder (GAD) do not show adequate response and remission. Thus, additional novel pharmacological agents are needed to increase treatment option for GAD. We aimed to investigate efficacy and safety of agomelatine in the treatment of GAD by conducting a meta-analysis. Methods An extensive search of multiple databases and clinical trial registries were conducted. Mean change in total scores on Hamilton Anxiety Rating Scale (HAM-A) from baseline to endpoint was our primary outcome measure. Secondary efficacy measures included response and remission rates, as defined by a 50% or greater reduction in HAM-A total scores and a score of 7 or less in HAM-A total scores at study endpoint respectively. Results Four published double blinded, randomized, placebo-controlled trials were included in this meta-analysis. Agomelatine more significantly (standardized mean difference = -0.56, p = 0.004) improved HAM-A total scores than placebo. The odds ratios (ORs) of agomelatine over placebo for response and remission rates were 3.75 (p < 0.00001) and 2.74 (p < 0.00001), respectively. Agomelatine was generally well tolerated with insignificance in dropout rate, somnolence, headache, nasopharyngitis, and dizziness compared with placebo. However, agomelatine showed significantly higher incidence of liver function increment (OR = 3.13, p = 0.01) and nausea (OR = 3.27, p = 0.02). Conclusion We showed that agomelatine may be another treatment option in patients with GAD. However, the results should be interpreted and translated into clinical practice with caution because the meta-analysis was based on limited numbers of clinical trials.
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- 2020
18. Association between exposure to polycyclic aromatic hydrocarbons and brain cortical thinning: The Environmental Pollution-Induced Neurological EFfects (EPINEF) study
- Author
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Young Noh, Ho Hyun Kim, Jaelim Cho, Sang Baek Koh, Woojin Kim, Juhwan Noh, Seong Kyung Cho, Hee Jin Kim, Sung Soo Oh, Dae Seock Shin, Hwasun Seo, Gayoung Seo, Jungwoo Sohn, Seung Koo Lee, Sang Won Seo, Jung Il Lee, Seongho Seo, Nak-Young Kim, Sun Young Kim, Changsoo Kim, and Heeseon Jang
- Subjects
Adult ,Male ,Environmental Engineering ,010504 meteorology & atmospheric sciences ,Urinary system ,Physiology ,Cortical thinning ,Environmental pollution ,010501 environmental sciences ,Verbal learning ,01 natural sciences ,Neuroimaging ,Republic of Korea ,medicine ,Environmental Chemistry ,Humans ,Polycyclic Aromatic Hydrocarbons ,Child ,Waste Management and Disposal ,0105 earth and related environmental sciences ,business.industry ,Neurotoxicity ,Neuropsychology ,Brain ,Environmental Exposure ,medicine.disease ,Pollution ,Quartile ,Female ,business ,Environmental Pollution ,Biomarkers - Abstract
Although some studies have suggested that exposure to polycyclic aromatic hydrocarbons (PAHs) induces neurodevelopmental disturbances in children and neurodegeneration in animals, the neurotoxic effect of PAH exposure is unclear in adults. The aim was to examine the associations of PAH exposure with brain structure and neuropsychological function in adults without known neurological diseases.This study included 421 men and 528 women dwelling in four cities in the Republic of Korea. Urinary concentrations of four PAH metabolites (1-hydroxypyrene, 2-naphthol, 1-hydroxyphenanthrene, and 2-hydroxyfluorene) were obtained. Participants underwent brain 3 T magnetic resonance imaging and neuropsychological tests. Cortical thickness and volume were estimated using the region-of-interest method. Separate generalized linear models were constructed for each sex, adjusting for age, years of education, cohabitation status, income, tobacco use, alcohol consumption, and vascular risk factors.The mean (standard deviation) age was 68.3 (6.6) years in men and 66.4 (6.1) years in women. In men, those in quartile 4 (versus quartile 1, the lowest) of urinary 2-naphthol concentration had cortical thinning in the global (β = -0.03, P = .02), parietal (β = -0.04, P = .01), temporal (β = -0.06, P .001), and insular lobes (β = -0.05, P = .02). Higher quartiles of urinary 2-naphthol concentration were associated with cortical thinning in the global (P = .01), parietal (P = .004), temporal (P .001), and insular lobes (P = .01). In women, those in quartile 4 (versus quartile 1) of urinary 1-hydroxypyrene concentration had cortical thinning in the frontal (β = -0.03, P = .006) and parietal lobes (β = -0.03, P = .003). Higher quartiles of urinary 1-hydroxypyrene concentration were associated with cortical thinning in the frontal (P = .006) and parietal lobes (P = .001). In both sexes, verbal learning and memory scores significantly declined with an increase in quartile of urinary 1-hydroxypyrene concentration.PAH exposure was associated with cortical thinning and decline in verbal learning and memory function in cognitively healthy adults. This suggests PAHs as an environmental risk factor for neurodegeneration.
- Published
- 2019
19. Impact of Transcranial Direct Current Stimulation on Cognitive Function, Brain Functional Segregation, and Integration in Patients with Mild Cognitive Impairment According to Amyloid-Beta Deposition and APOE ε4-Allele: A Pilot Study
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Donghyeon Kim, Nak-Young Kim, Hae-Ran Na, Sheng-Min Wang, TaeYeong Kim, Chang-Uk Lee, Dong Woo Kang, and Hyun Kook Lim
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Apolipoprotein E ,medicine.medical_specialty ,Amyloid beta ,medicine.medical_treatment ,Neurosciences. Biological psychiatry. Neuropsychiatry ,Stimulation ,Hippocampal formation ,Article ,03 medical and health sciences ,APOE ε4-allele ,mild cognitive impairment ,0302 clinical medicine ,Internal medicine ,mental disorders ,medicine ,030304 developmental biology ,0303 health sciences ,Transcranial direct-current stimulation ,medicine.diagnostic_test ,biology ,business.industry ,General Neuroscience ,Cognition ,Neuropsychological test ,Cardiology ,biology.protein ,amyloid beta deposition ,transcranial direct current stimulation ,Functional magnetic resonance imaging ,business ,030217 neurology & neurosurgery ,RC321-571 - Abstract
Anodal transcranial direct current stimulation (anodal-tDCS) is known to improve cognition and normalize abnormal network configuration during resting-state functional magnetic resonance imaging (fMRI) in patients with mild cognitive impairment (MCI). We aimed to evaluate the impact of sequential anodal-tDCS on cognitive functions, functional segregation, and integration parameters in patients with MCI, according to high-risk factors for Alzheimer’s disease (AD): amyloid-beta (Aβ) deposition and APOE ε4-allele status. In 32 patients with MCI ([18 F] flutemetamol-: n = 10, [18 F] flutemetamol+: n = 22, APOE ε4-: n = 13, APOE ε4+: n = 19), we delivered anodal-tDCS (2 mA/day, five times/week, for 2 weeks) over the left dorsolateral prefrontal cortex and assessed the neuropsychological test battery and resting-state fMRI measurements before and after 2 weeks stimulation. We observed a non-significant impact of an anodal-tDCS on changes in neuropsychological battery scores between MCI patients with and without high-risk factors of AD, Aβ retention and APOE ε4-allele. However, there was a significant difference in brain functional segregation and integration parameters between MCI patients with and without AD high-risk factors. We also found a significant effect of tDCS-by-APOE ε4-allele interaction on changes in the functional segregation parameter of the temporal pole. In addition, baseline Aβ deposition significantly associated negatively with change in global functional integrity of hippocampal formation. Anodal-tDCS might help to enhance restorative and compensatory intrinsic functional changes in MCI patients, modulated by the presence of Aβ retention and the APOE ε4-allele.
- Published
- 2021
20. Semi-Supervised Learning in Medical MRI Segmentation: Brain Tissue with White Matter Hyperintensity Segmentation Using FLAIR MRI
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Donghyeon Kim, ZunHyan Rieu, Se Won Oh, Minho Lee, Dong Woo Kang, Nak-Young Kim, Regina E. Y. Kim, Min Kyoung Lee, Hyun Kook Lim, Sheng-Min Wang, and Jee-Young Kim
- Subjects
medicine.medical_specialty ,Neurosciences. Biological psychiatry. Neuropsychiatry ,Brain tissue ,Semi-supervised learning ,Fluid-attenuated inversion recovery ,deep-learning ,01 natural sciences ,Article ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,FLAIR ,medicine ,Brain segmentation ,Segmentation ,0101 mathematics ,medicine.diagnostic_test ,business.industry ,General Neuroscience ,segmentation ,Magnetic resonance imaging ,Hyperintensity ,white-matter hyperintensity ,White matter hyperintensity ,T1w ,Radiology ,business ,030217 neurology & neurosurgery ,RC321-571 - Abstract
White-matter hyperintensity (WMH) is a primary biomarker for small-vessel cerebrovascular disease, Alzheimer’s disease (AD), and others. The association of WMH with brain structural changes has also recently been reported. Although fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) provide valuable information about WMH, FLAIR does not provide other normal tissue information. The multi-modal analysis of FLAIR and T1-weighted (T1w) MRI is thus desirable for WMH-related brain aging studies. In clinical settings, however, FLAIR is often the only available modality. In this study, we thus propose a semi-supervised learning method for full brain segmentation using FLAIR. The results of our proposed method were compared with the reference labels, which were obtained by FreeSurfer segmentation on T1w MRI. The relative volume difference between the two sets of results shows that our proposed method has high reliability. We further evaluated our proposed WMH segmentation by comparing the Dice similarity coefficients of the reference and the results of our proposed method. We believe our semi-supervised learning method has a great potential for use for other MRI sequences and will encourage others to perform brain tissue segmentation using MRI modalities other than T1w.
- Published
- 2021
21. P1‐505: THE CLINICAL USEFULNESS AND VALIDITY OF THE NOVEL TABLET‐BASED COGNITIVE SCREENING TEST IN PATIENTS WITH SUBJECTIVE COGNITIVE DECLINE AND AMNESTIC MILD COGNITIVE IMPAIRMENT
- Author
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Juoh Yun, Jiho Yeom, Juhee Chin, Byung Hwa Lee, Nak-Young Kim, Dae-seok Shin, and Duk L. Na
- Subjects
Epidemiology ,business.industry ,Health Policy ,Test (assessment) ,Psychiatry and Mental health ,Cellular and Molecular Neuroscience ,Developmental Neuroscience ,Cognitive screening ,Medicine ,In patient ,Neurology (clinical) ,Geriatrics and Gerontology ,Cognitive decline ,business ,Cognitive impairment ,Clinical psychology - Published
- 2018
22. Machine Learning-based Individual Assessment of Cortical Atrophy Pattern in Alzheimer’s Disease Spectrum: Development of the Classifier and Longitudinal Evaluation
- Author
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Samuel N. Lockhart, Hanna Cho, Jeong Hyeon Shin, Duk L. Na, Sang Won Seo, Dae Seock Shin, Yeshin Kim, Jin San Lee, Hee Jin Kim, Joon Kyung Seong, Nak-Young Kim, and Changsoo Kim
- Subjects
Male ,lcsh:Medicine ,Disease ,Similarity measure ,Machine learning ,computer.software_genre ,050105 experimental psychology ,Article ,Machine Learning ,03 medical and health sciences ,0302 clinical medicine ,Text mining ,Atrophy ,Alzheimer Disease ,medicine ,Dementia ,Humans ,0501 psychology and cognitive sciences ,Cognitive Dysfunction ,Longitudinal Studies ,lcsh:Science ,Cortical atrophy ,Aged ,Cerebral Cortex ,Multidisciplinary ,medicine.diagnostic_test ,business.industry ,05 social sciences ,lcsh:R ,Magnetic resonance imaging ,Middle Aged ,medicine.disease ,Magnetic Resonance Imaging ,Cohort ,lcsh:Q ,Female ,Artificial intelligence ,business ,computer ,030217 neurology & neurosurgery - Abstract
To develop a new method for measuring Alzheimer’s disease (AD)-specific similarity of cortical atrophy patterns at the individual-level, we employed an individual-level machine learning algorithm. A total of 869 cognitively normal (CN) individuals and 473 patients with probable AD dementia who underwent high-resolution 3T brain MRI were included. We propose a machine learning-based method for measuring the similarity of an individual subject’s cortical atrophy pattern with that of a representative AD patient cohort. In addition, we validated this similarity measure in two longitudinal cohorts consisting of 79 patients with amnestic-mild cognitive impairment (aMCI) and 27 patients with probable AD dementia. Surface-based morphometry classifier for discriminating AD from CN showed sensitivity and specificity values of 87.1% and 93.3%, respectively. In the longitudinal validation study, aMCI-converts had higher atrophy similarity at both baseline (p p p = 0.042), first year (p = 0.028), and third year visits (p = 0.027). The AD-specific atrophy similarity measure is a novel approach for the prediction of dementia risk and for the evaluation of AD trajectories on an individual subject level.
- Published
- 2018
23. P1-287: THE CORTICAL THINNING PATTERN ASSOCIATED WITH THE MILD BEHAVIORAL IMPAIRMENT IN PATIENTS WITH SUBJECTIVE COGNITIVE DECLINE, MILD COGNITIVE IMPAIRMENT AND DEMENTIA DUE TO ALZHEIMER'S DISEASE
- Author
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Duk L. Na, Juhee Chin, Dae-seok Shin, Hee Jin Kim, Hwajung Kim, Nak-Young Kim, Sang Won Seo, and Yeonwook Kang
- Subjects
medicine.medical_specialty ,Epidemiology ,business.industry ,Health Policy ,Cortical thinning ,Disease ,Audiology ,medicine.disease ,Psychiatry and Mental health ,Cellular and Molecular Neuroscience ,Developmental Neuroscience ,medicine ,Dementia ,In patient ,Neurology (clinical) ,Geriatrics and Gerontology ,Cognitive decline ,Cognitive impairment ,business - Published
- 2019
24. A Novel Angle Servo for Holographic Data Storage System
- Author
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Jooyoun Park, Kunyul Kim, Pil Sang Yoon, Jongyong Park, Kyu-Il Jung, and Nak Young Kim
- Subjects
3D optical data storage ,business.industry ,Computer science ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Physics::Optics ,Optical storage ,Holographic data storage ,Holographic Data Storage System ,Optics ,Reference beam ,Optical recording ,Computer data storage ,business ,Servo - Abstract
The control method for the angle servo of reference beam during reading recoded data images of a holographic data storage system is presented. The recording scheme with track offset is adopted in other to implement the proposed angle servo. Using only recorded data tracks the system generates the angle error signal of reference beam and implements the angle servo. Experiments have been performed on recording and reading data images to compensate angle Bragg mismatch.
- Published
- 2007
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