• BMB Reports
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• 제51권8호
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• pp.369-370
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• 2018

In previous studies, memory storage was localized to engram cells distributed across the brain. While these studies have provided an individual cellular profile of engram cells, their synaptic connectivity, or whether they follow Hebbian mechanisms, remains uncertain. Therefore, our recent study investigated whether synapses between engram cells exhibit selectively enhanced structural and functional properties following memory formation. This was accomplished using a newly developed technique called "dual-eGRASP". We found that the number and size of spines on CA1 engram cells that receive inputs from CA3 engram cells were larger than at other synapses. We further observed that this enhanced connectivity correlated with induced memory strength. CA3 engram synapses exhibited increased release probability, while CA1 engram synapses produced enhanced postsynaptic responses. CA3 engram to CA1 engram projections showed strong occlusion of long-term potentiation. We demonstrated that the synaptic connectivity of CA3 to CA1 engram cells was strengthened following memory formation. Our results suggest that Hebbian plasticity occurs during memory formation among engram cells at the synapse level.

• Applied Microscopy
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• 제48권4호
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• pp.102-109
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• 2018

Multiple synaptic boutons (MSBs) have been reported to be synapse with two or more postsynaptic terminals in one presynaptic terminal. These MSBs are known to be increased by various brain stimuli. In the motor cortex, increased number of MSB was observed in both acrobat training (AC) model and traumatic brain injury (TBI) model. Interestingly one is a physiological stimuli and the other is pathological insult. The purpose of this study is to compare the connectivity of MSBs between AC model and TBI model in the cerebral motor cortex, based on the hypothesis that the connectivity of MSBs might be different according to the models. The motor cortex was dissected from perfused brain of each experimental animal, the samples were prepared for routine transmission electron microscopy. The 60~70 serial sections were mounted on the one-hole grid and MSB was analyzed. The 3-dimensional analysis revealed that 94% of MSBs found in AC model synapse two postsynaptic spines from same dendrite. But, 28% MSBs from TBI models synapse two postsynaptic spines from different dendrite. This imply that the MSBs observed in motor cortex of AC model and TBI model might have different circuits for the processing the information.

• Applied Microscopy
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• 제46권2호
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• pp.100-104
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• 2016

Electron microscopy is currently the only available technique with a spatial resolution sufficient to identify fine neuronal processes and synaptic structures in densely packed neuropil. For large-scale volume reconstruction of neuronal connectivity, serial block-face scanning electron microscopy allows us to acquire thousands of serial images in an automated fashion and reconstruct neural circuits faster by reducing the alignment task. Here we introduce the whole reconstruction procedure of synaptic network in the rat hippocampal CA1 area and discuss technical issues to be resolved for improving image quality and segmentation. Compared to the serial section transmission electron microscopy, serial block-face scanning electron microscopy produced much reliable three-dimensional data sets and accelerated reconstruction by reducing the need of alignment and distortion adjustment. This approach will generate invaluable information on organizational features of our connectomes as well as diverse neurological disorders caused by synaptic impairments.

• Applied Microscopy
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• 제34권4호
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• pp.285-294
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• 2004

생쥐의 망막에서 아세틸콜린의 합성효소인 choline acetyltransferase (ChAT)에 대한 항체를 이용한 면역세포화학법으로 콜린성 무축삭세포를 동정하고 분포양상을 조사하였다. 콜린성 무축삭세포는 망막에서 세포체의 위치에 따라서 두 종류로 구분된다. 즉 속핵층에 세포체가 위치하고 세포돌기는 속얼기층의 a 아층판에 위치하는 세포와 세포체가 신경절세포층에 위치하면서 세포돌기는 b 아층판에 위치하는 세포이다. GABA 항체를 이용한 이중 면역염색 결과 모든 콜린성 무축삭세포가 GABA에 대한 염색반응성을 나타내었다. 전자현미경 관찰 결과 콜린성 무축삭세포의 연접회로가 속얼기층에서 관찰되었다. 콜린성 무축삭세포는 두극세포와 가장 많은 수입연접을 형성하고 있었으며, 이 외에 콜린성 무축삭세포와 염색되지 않은 무축삭세포와의 연접도 관찰되었다. 콜린성 무축삭세포의 수출연접의 주요 대상은 신경절세포로 속얼기층의 b 아층판에서 더 빈번하게 관찰되었다. 이러한 연구결과로 생쥐 망막의 콜린성 무축삭세포도 다른 종류의 포유류와 매우 유사한 특징을 가지고 있으며, 방향선택성 신경절세포로 신호가 전달되는 과정에서 중요한 역할을 할 것으로 생각된다.

• 생물정신의학
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• 제20권4호
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• pp.136-143
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• 2013

Objectives We reviewed cellular and synaptic dysconnectivity, disturbances in micro- and macro- circuitries, and neurodevelopmentally-derived disruptions of neural connectivity in the pathogenesis of schizophrenia. Method We reviewed the selected articles about disturbances in neural circuits which had been proposed as a pathogenetic mechanism of schizophrenia. Results The literature review reveals that schizophrenia may be a disease related to disturbance in neurodevelopmental mechanism, shown as 'a misconnection syndrome of neural circuit or neural network'. In descriptive psychopathological view, definition of a disorder of brain connectivity has limitation to explain other aspects of schizophrenia including deterministic strictness in thought process. Conclusion Schizophrenia is considered as a disorder of brain connectivity as well as a neurodevelopmental disorder related with genetic and environmental factors. We could make a suggestion that "JoHyeonByung (attunement disorder)" denotes the disturbances of psychic fine-tuning which correspond to the neural correlates of brain dysconnectivity metaphorically.

• Molecules and Cells
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• 제40권2호
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• pp.151-161
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• 2017

Proper synaptic function in neural circuits requires precise pairings between correct pre- and post-synaptic partners. Errors in this process may underlie development of neuropsychiatric disorders, such as autism spectrum disorder (ASD). Development of ASD can be influenced by genetic factors, including copy number variations (CNVs). In this study, we focused on a CNV occurring at the 16p11.2 locus in the human genome and investigated potential defects in synaptic connectivity caused by reduced activities of genes located in this region at Drosophila larval neuromuscular junctions, a well-established model synapse with stereotypic synaptic structures. A mutation of rolled, a Drosophila homolog of human mitogen-activated protein kinase 3 (MAPK3) at the 16p11.2 locus, caused ectopic innervation of axonal branches and their abnormal defasciculation. The specificity of these phenotypes was confirmed by expression of wild-type rolled in the mutant background. Albeit to a lesser extent, we also observed ectopic innervation patterns in mutants defective in Cdk2, Gq, and Gp93, all of which were expected to interact with Rolled MAPK3. A further genetic analysis in double heterozygous combinations revealed a synergistic interaction between rolled and Gp93. In addition, results from RT-qPCR analyses indicated consistently reduced rolled mRNA levels in Cdk2, Gq, and Gp93 mutants. Taken together, these data suggest a central role of MAPK3 in regulating the precise targeting of presynaptic axons to proper postsynaptic targets, a critical step that may be altered significantly in ASD.

• 한국컴퓨터정보학회논문지
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• 제7권1호
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• pp.1-7
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• 2002

최근에 컴포넌트에 기반한 소프트웨어 개발이 대학과 산업체의 중요 연구 대상이 되었다. 컴포넌트는 컴포넌트 저장소에 저장되는데 컴포넌트의 효율적인 검색은 컴포넌트에 기반한 소프트웨어 개발에 매우 중요하다. 이 논문에서 컴포넌트의 효율적인 검색을 위하여 새로운 가중치 함수를 사용한 신경 접속 행렬을 제안한다. 또한 부정 검색을 위한 신경 접속 행렬을 구하는 새로운 알고리즘을 제안하고 이를 증명한다. 마지막으로 논리 연산자를 사용한 질의에 대하여 효율적으로 행렬을 연산하는 과정을 제안한다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권5호
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• pp.657-663
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• 2016

In this work, a novel silicon (Si) based floating body synaptic transistor (SFST) is studied to mimic the transition from short-term memory to long-term one in the biological system. The structure of the proposed SFST is based on an n-type metal-oxide-semiconductor field-effect transistor (MOSFET) with floating body and charge storage layer which provide the functions of short- and long-term memories, respectively. It has very similar characteristics with those of the biological memory system in the sense that the transition between short- and long-term memories is performed by the repetitive learning. Spike timing-dependent plasticity (STDP) characteristics are closely investigated for the SFST device. It has been found from the simulation results that the connectivity between pre- and post-synaptic neurons has strong dependence on the relative spike timing among electrical signals. In addition, the neuromorphic system having direct connection between the SFST devices and neuron circuits are designed.

• 한국컴퓨터정보학회논문지
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• 제7권3호
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• pp.16-22
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• 2002

컴포넌트의 효율적인 검색은 컴포넌트에 기반한 소프트웨어 개발에 필수적이다. 패싯 방식은 컴포넌트 검색 방법의 하나로 많은 연구의 대상이다. 이 논문에서 여러 개의 패싯값에 대한 논리 부정 검색에 사용되는 가중치 신경 접속 행렬을 효율적으로 만드는 새로운 알고리즘을 제안한다. 이 알고리즘을 사용하여 연산에 드는 복잡도를 향상할 수 있다. 또한 여러 개의 서로 다른 패싯을 사용하는 경우 이에 대한 논리적인 검색이 가능하도록 새로운 연산 방법을 제안하다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.277.2-277.2
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• 2013

Petri dishes and glass slides have been widely used as general substrates for in vitro mammalian cell cultures due to their culture viability, optical transparency, experimental convenience, and relatively low cost. Despite the aforementioned benefit, however, the flat two-dimensional substrates exhibit limited capability in terms of realistically mimicking cellular polarization, intercellular interaction, and differentiation in the non-physiological culture environment. Here, we report a protocol of culturing embryonic rat hippocampal neurons on the electro-spun polymeric network and the results from examination of neuronal cell behavior and network formation on this culture platform. A combinatorial method of laser-scanning confocal fluorescence microscopy and live-cell imaging technique was employed to track axonal outgrowth and synaptic connectivity of the neuronal cells deposited on this model culture environment. The present microfiber-based scaffold supports the prolonged viability of three-dimensionally-formed neuronal networks and their microscopic geometric parameters (i.e., microfiber diameter) strongly influence the axonal outgrowth and synaptic connection pattern. These results implies that electro-spun fiber scaffolds with fine control over surface chemistry and nano/microscopic geometry may be used as an economic and general platform for three-dimensional mammalian culture systems, particularly, neuronal lineage and other network forming cell lines.