• 생물정신의학
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• 제4권2호
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• pp.194-197
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• 1997

Neural network models, also known as connectionist models or PDP models, simulate some functions of the brain and may promise to give insight in understanding the cognitive brain functions. The models composed of neuron-like elements that are linked into circuits can learn and adapt to its environment in a trial and error fashion. In this article, the history and principles of the neural network modeling are briefly reviewed, and its applications to psychiatry are discussed.

• 대한의용생체공학회:의공학회지
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• 제2권2호
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• pp.127-140
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• 1981

This paper describes the mechanism of information processing in the nervous system through neuron pool model which is consisted of six single neural models. In the neuron pool model, summation characteristic of stimulus satisfies those of real nervous system and output impulse rate increases linearly to the input stimulus. Occlusion phenomena of the neuron pool model is approached to those of real nervous system and also if the threshold potential within sutlirninal fringe is increased, facilitation phenomena appreared. Therefore, the results of this study suggest that we can construct large neuron pool with many single neural models and verify the mechanism of information processing in the wide part of nervous system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.60-64
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• 1995

The conventional neural network models are a parody of biological neural structures, and have very slow learning. In order to emulate some dynamic functions, such as learning and adaption, and to better reflect the dynamics of biological neurons, M.M. Gupta and D.H. Rao have developed a 'dynamic neural model'(DNU). Proposed neural unit model is to introduce some dynamics to the neuron transfer function, such that the neuron activity depends on internal states. Integrating an dynamic elementry processor within the neuron allows the neuron to act dynamic response Numerical examples are presented for a model system. Those case studies showed that the proposed DNU is so useful in practical sense.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.157-160
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• 1995

Neural networks potentially offer a general framework for modeling and control of nonlinear systems. The conventional neural network models are a parody of biological neural structures, and have very slow learning. In order to emulate some, dynamic functions, such as learning and adaption, and to better reflect the dynamics of biological neurons, M.M.Gupta and D.H.Rao have developed a 'dynamic neural model'(DNU). Proposed neural unit model is to introduce some dynamics to the neuron transfer function, such that the neuron activity depends on internal states. Numerical examples are presented for a model system. Those case studies showed that the proposed DNU is so useful in practical sense.

• 한국전기전자재료학회논문지
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• 제35권4호
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• pp.311-321
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• 2022

The report reviews recent research efforts in demonstrating a computing system whose operation principle mimics the dynamics of biological neurons. The temporal variation of the membrane potential of neurons is one of the key features that contribute to the information processing in the brain. We first summarize the neuron models that explain the experimentally observed change in the membrane potential. The function of ion channels is briefly introduced to understand such change from the molecular viewpoint. Dedicated circuits that can simulate the neuronal dynamics have been developed to reproduce the charging and discharging dynamics of neurons depending on the input ionic current from presynaptic neurons. Key elements include volatile memristors that can undergo volatile resistance switching depending on the voltage bias. This behavior called the threshold switching has been utilized to reproduce the spikes observed in the biological neurons. Various types of threshold switch have been applied in a different configuration in the hardware demonstration of neurons. Recent studies revealed that the memristor-based circuits could provide energy and space efficient options for the demonstration of neurons using the innate physical properties of materials compared to the options demonstrated with the conventional complementary metal-oxide-semiconductors (CMOS).

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 추계학술대회
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• pp.150-152
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• 2022

본 연구의 목적은 LTC(Liquid Time-constant Network)를 기반으로 감각 뉴런의 동작과 시냅스 가소성을 고려한 모델을 제안하는 것이다. 이를 위해 뉴런 연결 구조를 뉴런의 수가 증가하는 형태, 감소하는 형태, 증가 후 감소하는 형태, 감소 후 증가하는 형태의 4가지로 설정하여 실험을 진행하였다. 변경한 모델의 성능이 LTC에 비해 개선되었는지 알아보기 위한 데이터는 시계열 예측 데이터셋을 사용하였다. 실험 결과, 감각 뉴런의 모델링을 적용하는 것은 항상 성능 향상을 불러오는 것은 아니지만 데이터셋의 종류에 따라 적절히 학습 규칙을 선택하는 것을 통해 성능이 향상됨을 관찰하였다. 또한, 뉴런의 연결 구조는 4개 층 이하일 때 향상된 성능을 보였다.

• Biomolecules & Therapeutics
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• 제27권3호
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• pp.265-275
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• 2019

Technological advances of mankind, through the development of electrical and communication technologies, have resulted in the exposure to artificial electromagnetic fields (EMF). Technological growth is expected to continue; as such, the amount of EMF exposure will continue to increase steadily. In particular, the use-time of smart phones, that have become a necessity for modern people, is steadily increasing. Social concerns and interest in the impact on the cranial nervous system are increased when considering the area where the mobile phone is used. However, before discussing possible effects of radiofrequency-electromagnetic field (RF-EMF) on the human body, several factors must be investigated about the influence of EMFs at the level of research using in vitro or animal models. Scientific studies on the mechanism of biological effects are also required. It has been found that RF-EMF can induce changes in central nervous system nerve cells, including neuronal cell apoptosis, changes in the function of the nerve myelin and ion channels; furthermore, RF-EMF act as a stress source in living creatures. The possible biological effects of RF-EMF exposure have not yet been proven, and there are insufficient data on biological hazards to provide a clear answer to possible health risks. Therefore, it is necessary to study the biological response to RF-EMF in consideration of the comprehensive exposure with regard to the use of various devices by individuals. In this review, we summarize the possible biological effects of RF-EMF exposure.

• Journal of Korean Biological Nursing Science
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• 제4권1호
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• pp.101-112
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• 2002

Peripheral nerve injury results in plastic changes in the dorsal ganglia (DRG) and spinal cord, and is often complicated with neuropathic pain. The mechanisms underlying these changes are not known, but these changes seem to be most likely related to the neurotrophic factors. This study investigated the effects of mechanical peripheral nerve injury on expression of brain-derived neurotrophic factor(BDNF) in the DRG and spinal cord in rats. 1) Bennett model and Chung model groups showed significantly increased percentage of small, medium and large BDNF-immunoreactive neurons in the ipsilateral $L_4$ DRG compared with those in the contralateral side at 1 and 2 weeks of the injury. 2) In the ipsilateral $L_5$ DRG of the Chung model, percentage of medium and large BDNF-immunoreactive neurons increased significantly at 1 week, whereas that of large BDNF-immunoreactive neurons decreased at 2 week when compared with those in the contralateral side. The intensity of immunoreactivity of each neuron was lower in the ipsilateral than in the contralateral DRG. 3) In the spinal cord, the Bennett and Chung model groups showed a markedly increased BDNF-immunoreactivity in axonal fibers of both superficial and deeper laminae. The present study demonstrates that peripheral nerve injury in neuropathic models altered the BDNF expression in the DRG and spinal cord. This may suggest important roles of BDNF in sensory abnormalities after nerve injury and in protecting the large-sized neurons in the damaged DRG.

• 한국발생생물학회지:발생과생식
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• 제11권1호
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• pp.13-20
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• 2007

암컷 포유동물의 노화 과정에서 생식계는 체내 여러 시스템 가운데 가장 먼저 기능 저하가 나타난다. 생식 노화(reproductive aging) 과정 중인 암컷 포유동물은 비록 종 특이성이 있지만 주기성(cyclicity)의 소실과 같은 생식 능력의 감소와 함께 여러 기능들의 변화가 동반되면서 궁극적으로 인간의 폐경 현상과 같은 생식 능력 상실이 나타난다. 본 증설은 암컷 포유동물의 생식호르몬 축, 특히 신경내분비 회로의 노화에 대한 정보들과 노화 연구에 유용한 설치류 모델들을 소개하고자 한다. 암컷 설치류의 중년(middle age, 생후 $8{\sim}12$개월)은 인간의 폐경기 진입 직전에 해당되는 시기로, 이 시기에 시상하부 GnRH 분비의 맥동성과 급등(surge)이 현저히 지연되기 시작하고, 곧 이어 뇌하수체 LH 분비의 맥동성과 급등이 역시 약화 내지 지연된다. 노화와 관련된 GnRH-LH 신경내분비 활성의 결손은 시상하부 GnRH 뉴런의 활성을 조절하는 여러 자극(예, glutamate)들의 변화와 밀접하게 연관되어 있다. 많은 연구자들이 이러한 '시상하부 결손(hypothalamic defects)'이 생식 노화의 주된 요인임을 지지하지만, inhibin과 같은 난소 요인의 변화 역시 생식 노화의 유도와 관련된 것으로 보인다. 생식 노화를 연구함에 유용한 몇몇 설치류 모델이 있다; FSH 수용체 녹아웃(follitropin receptor knockout; FORKO) 생쥐 모델의 경우는 homozygous(null) 뿐만 아니라 heterozygous(haploinsufficient) 상태도 노화에 따른 난자/난포의 고갈을 나타낸다. Dioxin/aryl hydrocarbon 수용체 녹아웃 (AhRKO) 생쥐 모델도 유사한 상태를 유발할 수 있다. 생식 노화의 기작에 관한 연구는 삶의 질을 높이기 위한 수단들, 예를 들어 호르몬 보충요법(HRT)의 장단점을 평가하고 안전성을 제고하는데 도움이 될 것이다.

• 한국발생생물학회지:발생과생식
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• 제9권1호
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• pp.1-5
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• 2005

시상하부-뇌하수체-생식소(HPG) 호르몬 축은 유아기와 아동기에는 작동하지 않다가 사춘기 개시 직전에 활성화되는 흥분성 및 억제성 신호들의 복잡한 중추성 조절 네트워크에 의해 조절된다. 최근 주목받고 있는 kisspeptin은 KiSS-1 유전자의 펩타이드 산물로, 최초 orphan receptor로 클로닝된 G protein-coupled receptor 54(GPR54)의 내인성 리간드이다. KiSS-l은 본래 종양전이억제 유전자로 알려졌으나, 최근의 연구들은 KiSS-1/GPR54 시스템이 생식계의 주요한 조절자임을 시사하고 있다. 비록 생식 관련 호르몬 분비의 신경내분비적 조절에서 KiSS-1/GPR54 시스템의 정확한 역할은 아직 자세히 모르지만, 이 시스템은 생식호르몬 축에서의 일차적인 연결 고리일 수 있다. 중추적(icv) 또는 말초적(sc 또는 ip)으로 kisspeptin을 주사할 경우 시상하부-뇌하수체-생식소 축이 자극되어 혈중 LH 수준이 증가함이 설치류, 양, 원숭이 그리고 인간을 대상으로 한 실험들에서 관찰되었다. 이러한 kisspeptin의 효과는 시상하부 GnRH 신경계를 경유하여 나타나는 것으로 보이지만, 뇌하수체 전엽에 직접 작용할 수도 있다. GPR54 녹아웃 생쥐에서는 사춘기 개시의 소실과 생식소자극호르몬 저하성 생식소 기능저하증(hypogonadotropic hypogonadism, HH)이 나타났다. 따라서 kisspeptin 주사는 인간의 생식계 이상을 치료하기 위한 HPG 축을 활성화시키는 치료에 응용할 수 있을 것이다.