• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.257-258
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• 1998

To reveal the interconnected brain regions involved in human working memory, their functional connectivity was analyzed using principal component analysis (PCA). rCBF PET scans were peformed on 5 normal volunteers during the verbal and visual working memory tasks and PCA was applied. PCA produced the first principal components related with the increase of the difficulty and the second one which demonstrate the dissociation of verbal and visual memory system.

• Communications for Statistical Applications and Methods
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• 제31권1호
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• pp.87-104
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• 2024

Most functional magnetic resonance imaging (fMRI) studies in resting state have assumed that the functional connectivity (FC) between time series from distinct brain regions is constant. However, increased interest has recently been in quantifying possible dynamic changes in FC during fMRI experiments. FC study may provide insight into the fundamental workings of brain networks to brain activity. In this work, we focus on the specific problem of estimating the dynamic behavior of pairwise correlations between time courses extracted from two different brain regions. We compare the sliding-window techniques such as moving average (MA) and exponentially weighted moving average (EWMA), dynamic causality with vector autoregressive (VAR) model, dynamic conditional correlation (DCC) based on volatility, and the proposed alternative methods to use differencing and recursive residuals. We investigate the properties of those techniques in a series of simulation studies. We also provide an application with major depressive disorder (MDD) patient fMRI data to demonstrate studying dynamic correlations.

• 생물정신의학
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• 제24권2호
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• pp.68-74
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• 2017

Objectives It is well known that problem drinking is associated with alterations of brain structures and functions. Brain functions related to alcohol consumption can be determined by the resting state functional connectivity in various resting state networks (RSNs). This study aims to ascertain the alcohol effect on the structures forming predetermined RSNs by assessing their cortical thickness. Methods Twenty-six abstinent male patients with alcohol dependence and the same number of age-matched healthy control were recruited from an inpatient mental hospital and community. All participants underwent a 3T MRI scan. Averaged cortical thickness of areas constituting 7 RSNs were determined by using FreeSurfer with Yeo atlas derived from cortical parcellation estimated by intrinsic functional connectivity. Results There were significant group differences of mean cortical thicknesses (Cohen's d, corrected p) in ventral attention (1.01, < 0.01), dorsal attention (0.93, 0.01), somatomotor (0.90, 0.01), and visual (0.88, 0.02) networks. We could not find significant group differences in the default mode network. There were also significant group differences of gray matter volumes corrected by head size across the all networks. However, there were no group differences of surface area in each network. Conclusions There are differences in degree and pattern of structural recovery after abstinence across areas forming RSNs. Considering the previous observation that group differences of functional connectivity were significant only in networks related to task-positive networks such as dorsal attention and cognitive control networks, we can explain recovery pattern of cognition and emotion related to the default mode network and the mechanisms for craving and relapse associated with task-positive networks.

• Clinical Psychopharmacology and Neuroscience
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• 제16권4호
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• pp.449-460
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• 2018

Objective: Prior functional magnetic resonance imaging (fMRI) work has revealed that children/adolescents with disruptive behavior disorders (DBDs) show dysfunctional reward/non-reward processing of non-social reinforcements in the context of instrumental learning tasks. Neural responsiveness to social reinforcements during instrumental learning, despite the importance of this for socialization, has not yet been previously investigated. Methods: Twenty-nine healthy children/adolescents and 19 children/adolescents with DBDs performed the fMRI social/non-social reinforcement learning task. Participants responded to random fractal image stimuli and received social and non-social rewards/non-rewards according to their accuracy. Results: Children/adolescents with DBDs showed significantly reduced responses within the caudate and posterior cingulate cortex (PCC) to non-social (financial) rewards and social non-rewards (the distress of others). Connectivity analyses revealed that children/adolescents with DBDs have decreased positive functional connectivity between the ventral striatum (VST) and the ventromedial prefrontal cortex (vmPFC) seeds and the lateral frontal cortex in response to reward relative to non-reward, irrespective of its sociality. In addition, they showed decreased positive connectivity between the vmPFC seed and the amygdala in response to non-reward relative to reward. Conclusion: These data indicate compromised reinforcement processing of both non-social rewards and social non-rewards in children/adolescents with DBDs within core regions for instrumental learning and reinforcement-based decision-making (caudate and PCC). In addition, children/adolescents with DBDs show dysfunctional interactions between the VST, vmPFC, and lateral frontal cortex in response to rewarded instrumental actions potentially reflecting disruptions in attention to rewarded stimuli.

• 대한토목학회논문집
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• 제31권4B호
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• pp.383-391
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• 2011

본 연구에서는 수변생태벨트 조성 사업에 있어서 우선구간을 선정하기 위한 단절구간 평가 방법을 제시하였다. 대상 하천은 홍천강으로 하였으며, 홍천강 약 96 km를 2 km의 구간으로 구분하여, A1-P3의 48개 구간에 대한 도상조사 및 현장조사를 실시하였다. 단절 항목은 크게 연결성 및 생태적 기능성 단절로 구분하였으며, 연결성 단절에서는 토지이용 등의 면적 단절과 도로 및 제방 등의 선적 단절로 구분하였다. 또한 생태벨트의 기능성 단절은 기존 연구결과의 일부 항목을 도입하여 크게 하천 수로 및 하상구조, 수림대 및 식생, 하천구조물로 구분하여 평가하였다. 현장조사를 통하여 각각의 세부 항목별 단절 점수를 부여하였으며, 각 단절 항목별 평균하여 이를 등급화 하였다. 그 결과, F1-G2 구간에서 2등급 이상의 연결성 및 기능성 단절 등급을 보이는 것으로 나타났으며, 다른 구간에서는 연결성 단절이 2등급으로 높지만, 기능성 단절이 3-4등급으로 낮아 복원이 시급한 구간이 아닌 것으로 평가되었다. 본 연구 결과는 향후 수변생태벨트 조성 등의 하천복원 사업에 있어 대상 하천내 우선 사업구간 선정에 기여할 수 있을 것으로 보인다.

• 한국의류학회지
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• 제42권1호
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• pp.183-194
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• 2018

This study investigated the characteristics of Omni Channel and examined the influence of them on consumers' perceived functional value and emotional value as well as the effect of perceived functional value and emotional value on user's intention of use through Omni Channel. To verify the research model, the questionnaire survey was conducted on 20's to 40's men and women residing in Seoul and the metropolitan area by convenience sampling. The number of copies used for data analysis was 696. To verify the research model, factor analysis, reliability analysis, and structural equation model analysis were performed using AMOS 20.0. First, Omni Channel characteristics consisted of four factors: instant connectivity, location-based provability, interactivity, and entertainment. Second, the instant connectivity, location-based provability and entertainment positively influenced functional value and emotional value; however, the interactivity was significant only to the emotional value. Third, consumers' perceived value of Omni Channel characteristics had a significant effect on attitude. Fourth, the more favorable the attitude toward Omni Channel is higher for the intention to use Omni Channel.

• 한국산학기술학회논문지
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• 제17권9호
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• pp.559-569
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• 2016

본 연구에서는 교통연계성에 따른 각 권역별 네트워크 분석을 수행하여 우리나라의 국토공간 구조상에서 발생하는 지역 간 흐름을 살펴보고 그에 따른 향후 권역별 발전방향을 도출해보고자 한다. 이를 위해 국가교통DB센터에서 제공하는 2010년 전국 고속버스 OD 데이터를 활용하여 전국 단위의 교통 연계성을 먼저 살펴보고, 그 이후, 2010년 승용차 O/D 데이터를 활용하여 강원도, 경상남도, 경상북도, 전라남도, 전라북도, 충청도, 서울특별시 등 총 7개 권역(125개 시군+서울특별시)을 대상으로 네트워크 분석을 통해 권역 내 교통연계성을 살펴보았다. 분석결과, 우리나라는 수도권과 전라권, 경상권을 중심으로 하는 교통연계성이 강하게 나타남과 동시에 각 권역별로 내 외부 연계성이 상이하게 나타났다. 이는 곧 권역마다 차별적인 발전방안이 마련되어야 하는 근거를 시사하며 이에 본 연구에서는 연계성 분석결과와 더불어 대표적인 지역진단지표인 성장잠재력과 결합한 권역별 발전방향을 제시하였다. 본 연구는 국토공간의 균형적 발전과 각 권역별 맞춤형 정책개발 및 발전전략 수립의 기초자료로 활용될 수 있을 것으로 기대된다.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2012년도 춘계학술대회
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• pp.11-12
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• 2012

• 인지과학
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• 제29권3호
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• pp.161-192
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• 2018

부호화된 사건의 시간적 정보를 기반으로 한 인출은 일화기억의 중요한 통제기제 중 하나이다. 기억인출과 관련한 수많은 신경영상 연구들이 진행되었음에도 아직 시간적으로 구성된 일화기억의 인출에 관여하는 뇌신경연결망 패턴에 대해서는 알려진 바가 많지 않다. 본 연구에서는 두가지 다른 순차적 인출 뇌신경 기제를 구분하기 위하여 과제기반 기능적 연결성 다변량 패턴분석 방법을 사용하였다. 참가자들은 시간적 일화기억과제를 수행하였고, 순서대로 부호화된 기억자극을 순방향 혹은 역방향으로 인출하도록 지시를 받았다. 부분적으로 분류된 국소적 신경네트워크 패턴은 두 인출기제를 잘 구분하지 못한 반면, 기억과 관련된 인지통제 영역과 목표-지향적 인지기제처리에 관련된 것으로 알려진 여러 피질-피질하 노드들을 아우르는 전뇌신경네트워크 패턴은 시간적 일화기억 인출기제를 잘 구분하였다. 이 영역들은 측면/내측 전전두엽 영역, 하부 두정엽, 중간 측두회, 선조체 영역 등을 포함하며 기계학습을 이용한 분류에서 높은 분류 예측률을 보였다. 본 연구의 결과는 일화기억의 시간적 인출기제에 관여하는 피질-피질하 여러 영역의 관여를 확인하였고, 대역적 네트워크 패턴의 기능적 연결성이 질적으로 다른 인출기제에 관여함을 확인하였다는데에 중요성을 갖는다.

• 대한의용생체공학회:의공학회지
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• 제26권4호
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• pp.223-230
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• 2005

This paper presents a new approach to investigate spatial correlation between independent components of brain alpha activity in functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). To avoid potential problems of simultaneous fMRI and EEG acquisitions in imaging pure alpha activity, data from each modality were acquired separately under a 'three conditions' setup where one of the conditions involved closing eyes and relaxing, thus making it conducive to generation of alpha activity. The other two conditions -- eyes open in a lighted room or engaged in a mental arithmetic task, were designed to attenuate alpha activity. Using a Mixture Density Independent Component Analysis (MD-ICA) that incorporates flexible non-linearity functions into the conventional ICA framework, we could identify the spatiotemporal components of fMRI activations and EEG activities associated with the alpha rhythm. Then, the sources of the individual EEG alpha activity component were localized by a Maximum Entropy (ME) method that is specially designed to find the most probable dipole distribution minimizing the localization error in sense of LMSE. The resulting active dipoles were spatially transformed to 3D MRls of the subject and compared to fMRI alpha activity maps. A good spatial correlation was found in the spatial distribution of alpha sources derived independently from fMRI and EEG, suggesting the proposed method can localize the cortical areas responsible for generating alpha activity successfully in either fMRI or EEG. Finally a functional connectivity analysis was applied to show that alpha activity sources of both modalities were also functionally connected to each other, implying that they are involved in performing a common function: 'the generation of alpha rhythms'.