Dynamic effective connectivity in resting state fMRI

Park, Hae-Jeong,Friston, Karl J.,Pae, Chongwon,Park, Bumhee,Razi, Adeel ACADEMIC PRESS 2018 NEUROIMAGE Vol.180 No.2

<▼1><P>Context-sensitive and activity-dependent fluctuations in connectivity underlie functional integration in the brain and have been studied widely in terms of synaptic plasticity, learning and condition-specific (e.g., attentional) modulations of synaptic efficacy. This dynamic aspect of brain connectivity has recently attracted a lot of attention in the resting state fMRI community. To explain dynamic functional connectivity in terms of directed effective connectivity among brain regions, we introduce a novel method to identify dynamic effective connectivity using spectral dynamic causal modelling (spDCM). We used parametric empirical Bayes (PEB) to model fluctuations in directed coupling over consecutive windows of resting state fMRI time series. Hierarchical PEB can model random effects on connectivity parameters at the second (between-window) level given connectivity estimates from the first (within-window) level. In this work, we used a discrete cosine transform basis set or eigenvariates (i.e., expression of principal components) to model fluctuations in effective connectivity over windows. We evaluated the ensuing dynamic effective connectivity in terms of the consistency of baseline connectivity within default mode network (DMN), using the resting state fMRI from Human Connectome Project (HCP). To model group-level baseline and dynamic effective connectivity for DMN, we extended the PEB approach by conducting a multilevel PEB analysis of between-session and between-subject group effects. Model comparison clearly spoke to dynamic fluctuations in effective connectivity – and the dynamic functional connectivity these changes explain. Furthermore, baseline effective connectivity was consistent across independent sessions – and notably more consistent than estimates based upon conventional models. This work illustrates the advantage of hierarchical modelling with spDCM, in characterizing the dynamics of effective connectivity.</P></▼1><▼2><P><B>Highlights</B></P><P>•<P>We describe efficient estimation of dynamics in resting state effective connectivity.</P>•<P>Spectral DCM and PEB are used to model fluctuations in neuronal coupling over time.</P>•<P>Dynamics in responses are explained in terms of its causes (effective connectivity).</P>•<P>Baseline and dynamic components of the default mode connectivity are identified.</P></P></▼2>

Activation of the Occipital Cortex and Deactivation of the Default Mode Network During Working Memory in the Early Blind

Park, Hae-Jeong,Chun, Ji-Won,Park, Bumhee,Park, Haeil,Kim, Joong Il,Lee, Jong Doo,Kim, Jae-Jin Cambridge University Press 2011 JOURNAL- INTERNATIONAL NEUROPSYCHOLOGICAL SOCIETY Vol.17 No.3

<B>Abstract</B><P>Although blind people heavily depend on working memory to manage daily life without visual information, it is not clear yet whether their working memory processing involves functional reorganization of the memory-related cortical network. To explore functional reorganization of the cortical network that supports various types of working memory processes in the early blind, we investigated activation differences between 2-back tasks and 0-back tasks using fMRI in 10 congenitally blind subjects and 10 sighted subjects. We used three types of stimulus sequences: words for a verbal task, pitches for a non-verbal task, and sound locations for a spatial task. When compared to the sighted, the blind showed additional activations in the occipital lobe for all types of stimulus sequences for working memory and more significant deactivation in the posterior cingulate cortex of the default mode network. The blind had increased effective connectivity from the default mode network to the left parieto-frontal network and from the occipital cortex to the right parieto-frontal network during the 2-back tasks than the 0-back tasks. These findings suggest not only cortical plasticity of the occipital cortex but also reorganization of the cortical network for the executive control of working memory. (<I>JINS</I>, 2011, <I>17</I>, 407-422)</P>

A metal-free and mild approach to 1,3,4-oxadiazol-2(3<i>H</i>)-ones <i>via</i> oxidative C-C bond cleavage using molecular oxygen

Lim, Bumhee,Park, Seunggun,Park, Jae Hyun,Gam, Jongsik,Kim, Sanghee,Yang, Jung Woon,Lee, Jeeyeon The Royal Society of Chemistry 2018 Organic & Biomolecular Chemistry Vol.16 No.12

<P>A mild metal-free approach to 1,3,4-oxadiazol-2(3<I>H</I>)-ones <I>via</I> 1,3,4-oxadiazin-5(6<I>H</I>)-ones is described. This novel transformation, promoted by the electron-withdrawing <I>p</I>-substituents on the phenyl group at the α-carbonyl position, features a tandem reaction consisting of oxidative hydroxylation and C-C bond cleavage using molecular oxygen. The method utilizes K2CO3 in CH3CN without any oxidants, transition metals, or additives, enabling the tunable synthesis of 1,3,4-oxadiazin-5(6<I>H</I>)-ones, 1,3,4-oxadiazol-2(3<I>H</I>)-ones, and α-ketoamides under mild aerobic conditions.</P>

Blood lead exposure in COPD

( Joo Hun Park ),( Eunyoung Lee ),( Bumhee Park ),( Yun-jung Jung ),( Woo Young Chung ),( Ji Eun Park ),( Keu Sung Lee ),( Seung Soo Sheen ),( Sung Chul Hwang ),( Kwang Joo Park ) 대한결핵 및 호흡기학회 2019 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.127 No.-

Background: The association between blood lead levels and increased mortality was reported on a worldwide level. However, no study has been undertaken concerning the blood lead levels based on COPD and risk factors of COPD. Therefore, this study was conducted to examine the blood lead levels according to COPD and clinical variables associated with COPD. Methods: Data (total number = 36,813) were obtained from Korean National Health and Nutrition Examination Survey from 2008 to 2013. Multivariate linear regression analyses were performed to determine variables associated with elevated blood lead levels. Results: Blood lead levels were higher among older subjects, men, smokers, COPD, lower education group, and lower income groups (p<0.05). The blood lead levels in COPD group were higher than in the non-COPD group regardless of smoking status (p<0.05). Multivariate analysis demonstrated that older age, male sex, smoking, and education level were independently associated with higher blood lead levels, whereas COPD was not (p<0.05). Conclusion : This study demonstrated that smoking status and education level along with old age and male sex were independently associated with higher blood lead levels, however COPD was not, suggesting that the management of co-existing factors for COPD, such as smoking and socioeconomic factors is important.

Discordance in Secular Trends of Bone Mineral Density Measurements in Different Ages of Postmenopausal Women

Kim Kwang Yoon,Park Jaesun,Yang Sungwon,Shin Junghwa,Park Ji Hyun,Park Bumhee,Kim Bom Taeck 대한의학회 2023 Journal of Korean medical science Vol.38 No.42

Background: Age-adjusted bone mineral density (BMD) in postmenopausal women decreases in developed countries whereas incidence of osteoporotic fracture decreases or remains stable. We investigated secular trends of bone density from 2008 to 2017 among different age groups of postmenopausal women. Methods: We analyzed BMD data obtained from health check-ups of 4,905 postmenopausal women during three survey cycles from 2008 to 2017. We divided them into 3 groups by age (50–59 years, 60–69 years, and 70 years or more) and observed the transition of lumbar and femoral BMD in each group, before and after adjusting for variables that may affect BMD. Results: Age-adjusted BMD, bone mineral content (BMC), and T-score demonstrated a declining trend over the survey period at lumbar spine (−2.8%), femur neck (−3.5%) and total femur (−4.3%), respectively. In the analysis for the age groups, the BMD, BMC, and T-score presented linear declining trend (−6.1%) in younger postmenopausal women while women aged over 70 or more showed linear increasing trends (+6.3%) at lumbar spine during the survey period. Femoral neck and total femur BMD demonstrated a declining linear trend only in the 50–59 and 60–69 years groups (−5.5%, −5.2%, respectively), but not in the 70 years or more group. Conclusion: BMD in younger postmenopausal women has decreased considerably but has increased or plateaued in elderly women. This discordance of BMD trends among different age groups may contribute to decreased incidence of osteoporotic fracture despite a recent declining BMD trend in postmenopausal women.

Cerebellar Gray Matter Volume and its Role in Executive Function, and Attention: Sex Differences by Age in Adolescents

Hayeon Kim(Hayeon Kim),Bumhee Park(Bumhee Park),Shin-Young Kim(Shin-Young Kim),Jiyea Kim(Jiyea Kim),Bora Kim(Bora Kim),Kyu-In Jung(Kyu-In Jung),Seung-Yup Lee(Seung-Yup Lee),Yerin Hyun(Yerin Hyun),Bung 대한정신약물학회 2022 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.20 No.4

Objective: This research measures the regional GMV (rGMV) of the cerebellum, attention, Executive Function (EF) and we aimed to identify their correlation and sex differences in children and adolescents. Methods: Subjects comprised 114 children (male = 62, female = 52, 12.44 ± 2.99 years old) from South Korea. Participants were divided into three groups by age (age 6−9, 10−13, and 14−17). The Stroop Color and Word Test (SCWT), Wisconsin Card Sorting Test (WCST), and Advanced Test of Attention (ATA) were used to estimate executive function. Magnetic resonance imaging (MRI) images were analyzed with Regional Voxel-Based Morphometry Analysis. Results: The correlations between cerebellar rGMV and SCWT, WCST, and ATA subcategories showed difference by age and sex. In 6−9 age group, girls showed more overall correlations with cerebellar regions than boys, in WCST Categories Completed and ATA results. In age 10−13 group, more regions of cerebellum corresponded to SCWT subcategories in girls. Nevertheless, more correlation between cerebellar rGMV, WCST subcategories and some ATA subtests were observed in boys in the same age group. In the adolescent group, aged 14−17, boys showed more correlation with cerebellar rGMV, while girls showed little correlation. Conclusion: This study highlights that sex-different cerebellum maturation in adolescence might be correlated with EF and attention. These results provides evidence that cerebellum modulates higher cognitive functioning during child development.

High Thermal Conductive Natural Rubber Composites Using Aluminum Nitride and Boron Nitride Hybrid Fillers

( June-young Chung ),( Bumhee Lee ),( In-kyung Park ),( Hyun Ho Park ),( Heon Seob Jung ),( Joon Chul Park ),( Hyun Chul Cho ),( Jae-do Nam ) 한국고무학회 2020 엘라스토머 및 콤포지트 Vol.55 No.1

Herein, we investigated the thermal conductivity and thermal stability of natural rubber composite systems con­taining hybrid fillers of boron nitride (BN) and aluminum nitride (AlN). In the hybrid system, the bimodal distribution of polygonal AlN and planar BN particles provided excellent filler-packing efficiency and desired energy path for phonon transfer, resulting in high thermal conductivity of 1.29 W/mK, which could not be achieved by single filler composites. Fur­ther, polyethylene glycol (PEG) was compounded with a commonly used naphthenic oil, which substantially increased ther­mal conductivity to 3.51 W/mK with an excellent thermal stability due to facilitated energy transfer across the filler-filler interface. The resulting PEG-incorporated hybrid composite showed a high thermal degradation temperature (T₂) of 290℃, a low coefficient of thermal expansion of 26.4 ppm/℃, and a low thermal distortion parameter of 7.53 m/K, which is well over the naphthenic oil compound. Finally, using the Fourier's law of conduction, we suggested a modeling methodology to evaluate the cooling performance in thermal management system.

Effective connectivity during working memory and resting states: A DCM study

Jung, Kyesam,Friston, Karl J.,Pae, Chongwon,Choi, Hanseul H.,Tak, Sungho,Choi, Yoon Kyoung,Park, Bumhee,Park, Chan-A,Cheong, Chaejoon,Park, Hae-Jeong Elsevier 2018 NeuroImage Vol.169 No.-

<P><B>Abstract</B></P> <P>Although the relationship between resting-state <I>functional</I> connectivity and task-related activity has been addressed, the relationship between task and resting-state directed or <I>effective</I> connectivity – and its behavioral concomitants – remains elusive. We evaluated effective connectivity under an N-back working memory task in 24 participants using stochastic dynamic causal modelling (DCM) of 7 T fMRI data. We repeated the analysis using resting-state data, from the same subjects, to model connectivity among the same brain regions engaged by the N-back task. This allowed us to: (i) examine the relationship between intrinsic (task-independent) effective connectivity during resting (A<SUB>rest</SUB>) and task states (A<SUB>task</SUB>), (ii) cluster phenotypes of task-related changes in effective connectivity (B<SUB>task</SUB>) across participants, (iii) identify edges (B<SUB>task</SUB>) showing high inter-individual effective connectivity differences and (iv) associate reaction times with the similarity between B<SUB>task</SUB> and A<SUB>rest</SUB> in these edges. We found a strong correlation between A<SUB>rest</SUB> and A<SUB>task</SUB> over subjects but a marked difference between B<SUB>task</SUB> and A<SUB>rest</SUB>. We further observed a strong clustering of individuals in terms of B<SUB>task</SUB>, which was not apparent in A<SUB>rest</SUB>. The task-related effective connectivity B<SUB>task</SUB> varied highly in the edges from the parietal to the frontal lobes across individuals, so the three groups were clustered mainly by the effective connectivity within these networks. The similarity between B<SUB>task</SUB> and A<SUB>rest</SUB> at the edges from the parietal to the frontal lobes was positively correlated with 2-back reaction times. This result implies that a greater change in context-sensitive coupling – from resting-state connectivity – is associated with faster reaction times. In summary, task-dependent connectivity endows resting-state connectivity with a context sensitivity, which predicts the speed of information processing during the N-back task.</P>

High-Frequency Electrical Characterization of a New Coaxial Silicone Rubber Socket for High-Bandwidth and High-Density Package Test

Park, Junyong,Kim, Hyesoo,Kim, Jonghoon J.,Kim, Dong-Hyun,Son, Kyungjune,Kim, Subin,Lee, Seongsoo,Cho, Kyungjun,Bae, Bumhee,Ha, Dongho,Bae, Michael,Kim, Joungho IEEE 2018 IEEE transactions on components, packaging, and ma Vol.8 No.12

<P>This paper, for the first time, proposes and verifies a new coaxial silicone rubber socket for high-bandwidth and high-density package test using a fabricated sample. In addition, this paper also characterizes and verifies the coaxial silicone rubber socket. Because of the proposed coaxial socket’s novel coaxial structure, the proposed socket successfully achieves the electrical performance improvement. For verification, we compare the proposed socket and the previous noncoaxial socket in time domain. The proposed socket has greater eye height and eye width in the measured eye diagram than those of the noncoaxial socket. Moreover, the slope in the eye diagram is also improved in the case of the proposed socket. Therefore, the measured eye diagram for the coaxial socket shows the improvement in electrical performances. This paper also characterizes the equivalent RLGC model for the coaxial silicone rubber socket. In order to verify the RLGC model, we compare the insertion losses and eye diagrams from measurement, 3-D electromagnetic simulation, and the proposed RLGC model, respectively. Their insertion losses are comparable up to 20 GHz. Furthermore, the obtained eye diagrams are almost identical at the data rate of 9.6 Gb/s. In conclusion, this paper successfully proposes, verifies, and characterizes a new coaxial silicone rubber socket for the first time.</P>

Impact of Bronchiectasis on Incident NTM Pulmonary Disease: A 10-year National Cohort Study

( Bumhee Yang ),( Hyun Lee ),( Sun-Hyung Kim ),( Jiin Ryu ),( Taehee Kim ),( Yong Suk Jo ),( Youlim Kim ),( Hye Yun Park ),( Young Ae Kang ),( Seung Jun Lee ),( Ji-Yong Moon ),( Seung Won Ra ),( Sang- 대한결핵 및 호흡기학회 2020 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.128 No.0

Background Despite a well-established relationship between bronchiectasis and non-tuberculous mycobacterial pulmonary disease (NTM-PD), it is unclear whether the presence of bronchiectasis increases the risk of new NTM-PD. Methods We performed a population-based, matched cohort study of adults aged 20 years with bronchiectasis using data obtained from the Korean National Health Insurance Service National Sample Cohort database between 2003 and 2013. We evaluated the incidence rate and risk of NTM-PD in the bronchiectasis cohort versus the matched cohort. We also assessed the risk factors of incident NTM-PD in bronchiectasis patients. Results During the median follow-up duration of 6.1 years, the age- and sex-adjusted incidence of NTM-PD was 109.1/100,000 person-years in the bronchiectasis cohort and 5.6/100,000 person-years in the matched cohort (hazard ratio [HR] = 22.8, 95% confidence interval [CI] = 14.0-37.0, p <0.001). Multivariable analyses revealed that age (adjusted HR for patients aged 50-59 = 5.84, 95% CI = 2.05-16.6), female sex (adjusted HR = 1.64, 95% CI = 1.11-2.42), and previous pulmonary tuberculosis (adjusted HR = 4.89, 95% CI = 3.28-7.29) were associated with increased risk of incident NTM-PD in bronchiectasis patients. Conclusion Risk of incident NTM-PD was appr oximately 23-fold greater in patients with bronchiectasis than in those without bronchiectasis. Age (the greatest risk was among patients aged 50-59), female sex, and previous pulmonary tuberculosis were risk factors for incident NTM-PD in bronchiectasis patients.