• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.550-554
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• 1997

Acoustic or sound noise due to gradient pulsing has been one of the problems in MRI, both in patient scanning as well as in many areas of psychiatric and neuroscience research, such as unctional MRI (fMRI). Our recent observations in MRI or the visual and motor cortex show very different results with sound noise in comparison with the results obtained without sound noise. Although a number of ideas has been suggested in the literature about the possible elimination or reduction of sound noise, progress has been slow due to the basic role of gradient pulsing in MR imaging. Therefore, we report on some typical behavior of sound noise observed from MRI scanners and the analyses of their characteristics. Data are obtained both from a commercial MRI scanner (GE Signa 1.5-T EPI system).

• Annals of Clinical Neurophysiology
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• v.23 no.2
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• pp.69-81
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• 2021

Cortico-cortical evoked potential (CCEP) mapping is a rapidly developing method for visualizing the brain network and estimating cortical excitability. The CCEP comprises the early N1 component the occurs at 10-30 ms poststimulation, indicating anatomic connectivity, and the late N2 component that appears at < 200 ms poststimulation, suggesting long-lasting effective connectivity. A later component at 200-1,000 ms poststimulation can also appear as a delayed response in some studied areas. Such delayed responses occur in areas with changed excitability, such as an epileptogenic zone. CCEP mapping has been used to examine the brain connections causally in functional systems such as the language, auditory, and visual systems as well as in anatomic regions including the frontoparietal neocortices and hippocampal limbic areas. Task-based CCEPs can be used to measure behavior. In addition to evaluations of the brain connectome, single-pulse electrical stimulation (SPES) can reflect cortical excitability, and so it could be used to predict a seizure onset zone. CCEP brain mapping and SPES investigations could be applied both extraoperatively and intraoperatively. These underused electrophysiologic tools in basic and clinical neuroscience might be powerful methods for providing insight into measures of brain connectivity and dynamics. Analyses of CCEPs might enable us to identify causal relationships between brain areas during cortical processing, and to develop a new paradigm of effective therapeutic neuromodulation in the future.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.614-616
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• 2021

The world faces difficulties in terms of eye care, including treatment, quality of prevention, vision rehabilitation services, and scarcity of trained eye care experts. However, it is difficult to develop a method for classifying various ocular diseases because the existing dataset for retinal image disclosure does not consist of various diseases found in clinical practice. We propose a method for classifying ocular diseases using the Retinal Fundus Multi-disease Image Dataset (RFMiD), a dataset published in the ISBI-2021 challenge. Our goal is to develop a robust and generalizable model for screening retinal images into normal and abnormal categories. The performance of the proposed model shows a value of 0.9782 for the test dataset as an area under the curve (AUC) score.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.289-290
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• 2022

Arteriosclerosis is a disease in which the carotid vessel wall becomes thick, and it is important to monitor the thickness of the vessel wall for diagnosis. In this study, we propose a model for extracting 324 radiomics features from carotid MRI images and diagnosing arteriosclerosis using machine learning techniques. We learned a total of four classification models: logistic regression, support vector machine, random forest, and XGBoost through radiomics features. XGBoost model, which showed the highest performance in 5-fold cross-validation, shows the results of accuracy 0.9023, sensitivity 0.9517, specificity 0.8035, AUC 0.8776.

• Journal of The Korean Association For Science Education
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• v.29 no.7
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• pp.751-758
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• 2009

The purpose of this study was to investigate brain activation pattern and functional connectivity network during classification on the biological phenomena. Twenty six right-handed healthy science teachers volunteered to be in the present study. To investigate participants' brain activities during the tasks, 3.0T fMRI system with the block experimental-design was used to measure BOLD signals of their brain. According to the analyzed data, superior, middle and inferior frontal gyrus, superior and inferior parietal lobule, fusiform gyrus, lingual gyrus, and bilateral cerebellum were significantly activated during participants' carrying-out classification. The network model was consisting of six nodes (ROIs) and its fourteen connections. These results suggested the notion that the activation and connections of these regions mean that classification is consist of two sub-network systems (top-down and bottom-up related) and it functioning reciprocally. These results enable the examination of the scientific classification process from the cognitive neuroscience perspective, and may be used as basic materials for developing a teaching-learning program for scientific classification such as brain-based science education curriculum in the science classrooms.

• Journal of Ginseng Research
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• v.44 no.2
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• pp.341-349
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• 2020

Background: The replicative senescence of human dermal fibroblasts (HDFs) is accompanied by growth arrest. In our previous study, the treatment of senescent HDFs with Rg3(S) lowered the intrinsic reactive oxygen species (ROS) levels and reversed cellular senescence by inducing peroxiredoxin-3, an antioxidant enzyme. However, the signaling pathways involved in Rg3(S)-induced senescence reversal in HDFs and the relatedness of the stereoisomer Rg3(R) in corresponding signaling pathways are not known yet. Methods: We performed senescence-associated β-galactosidase and cell cycle assays in Rg3(S)-treated senescent HDFs. The levels of ROS, adenosine triphosphate (ATP), and cyclic adenosine monophosphate (cAMP) as well as the mitochondrial DNA copy number, nicotinamide adenine dinucleotide (NAD)⁺/1,4-dihydronicotinamide adenine dinucleotide (NADH) ratio, and NAD-dependent sirtuins expression were measured and compared among young, old, and Rg3(S)-pretreated old HDFs. Major signaling pathways of phosphatidylinositol 3-kinase/Akt, 5' adenosine monophosphate-activated protein kinase (AMPK), and sirtuin 1/3, including cell cycle regulatory proteins, were examined by immunoblot analysis. Results: Ginsenoside Rg3(S) reversed the replicative senescence of HDFs by restoring the ATP level and NAD⁺/NADH ratio in downregulated senescent HDFs. Rg3(S) recovered directly the cellular levels of ROS and the NAD⁺/NADH ratio in young HDFs inactivated by rotenone. Rg3(S) mainly downregulated phosphatidylinositol 3-kinase/Akt through the inhibition of mTOR by cell cycle regulators like p53/p21 in senescent HDFs, whereas Rg3(R) did not alter the corresponding signaling pathways. Rg3(S)-activated sirtuin 3/PGC1α to stimulate mitochondrial biogenesis. Conclusion: Cellular molecular analysis suggests that Rg3(S) specifically reverses the replicative senescence of HDFs by modulating Akt-mTOR-sirtuin signaling to promote the biogenesis of mitochondria.

• Journal of Acupuncture Research
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• v.20 no.5
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• pp.172-186
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• 2003

Acupuncture therapy has demonstrated efficacy in several clinical areas, and of these areas the understanding of pain has progressed immensely in the last two decades. The underlying mechanisms of acupuncture in general and the analgesic effect in particular are still not clearly delineated. The leading hypothesis include the effects of local stimulation, neuronal gating, release of endogenous opiates, and the placebo effect. Accumulating evidence suggests that the central nervous system(CNS) is essential for the processing of these effects, via its modulation of the autonomic nervous system, neuro-immune system, and hormonal regulation. These processes tap into basic survival mechanisms. As such, understanding the effects of acupuncture within a neuroscience-based framework becomes vital. We propose a model which incorporates the stress-induced hypothalamus-pituitary-adrenal axis(HPA-axis) model of Akil et al., the cholinergic anti-inflamatory observations of Tracey et al., and Petrovic et al.

• Molecules and Cells
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• v.40 no.4
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• pp.271-279
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• 2017

Ran-binding protein family member, RanBP9 has been reported in various basic cellular mechanisms and neuropathological conditions including schizophrenia. Previous studies have reported that RanBP9 is highly expressed in the mammalian brain and retina; however, the role of RanBP9 in retinal development is largely unknown. Here, we present the novel and regulatory roles of RanBP9 in retinal development of a vertebrate animal model, zebrafish. Zebrafish embryos exhibited abundant expression of ranbp9 in developing brain tissues as well as in the developing retina. Yeast two-hybrid screening demonstrated the interaction of RanBP9 with Mind bomb, a component of Notch signaling involved in both neurogenesis and neural disease autism. The interaction is further substantiated by co-localization studies in cultured cells. Knockdown of ranbp9 resulted in retinal dysplasia with defective proliferation of retinal cells, downregulation of neuronal differentiation marker huC, elevation of neural proliferation marker her4, and alteration of cell cycle marker p57kip2. Expression of the $M{\ddot{u}}ller$ glial cell marker glutamine synthase was also affected in knockdown morphants. Our results suggest that Mind bomb-binding partner RanBP9 plays a role during retinal cell development of zebrafish embryogenesis.

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.655-658
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• 2011

기초의학 강의 요원의 부족은 교육에 대한 부담과 연구활동 위축이라는 이중고를 초래하고 있다. 기초의학 강의의 효율성을 높이기 위하여 다양한 연구 및 해결책이 제시되어 왔으며, 통합강의 역시 그 대안의 하나로서 대두되고 있다. 따라서 본 연구에서는 새롭게 부각되고 있는 기초의학 통합강의에 대한 가상강의(cyber lecture) 적용의 실효성과 타당성을 설문조사와 교과목 운영의 경험을 중심으로 분석하였다. 설문조사에 대해 학생들은 가상강의의 내용, 난이도, 진행 및 멀티미디어 컨텐츠 등에 대해 대체로 만족스러운 의견을 제시하였다. 또한 가상강의가 통합강의 운영을 보완해주는데 효율적일 것이라는 의견과 더불어, 향후 통합강의에서 가상강의의 비중을 학대할 필요성에 대해서도 찬성의견이 반대의견보다 지배적임을 알 수 있었다. 뿐만 아니라, 통합강의 실습의 일부분을 가상강의에서 운영하는 방안에 대해서도 대체로 긍정적이었다. 통계분석 결과, 가상강의에 대해 긍정적이거나 부정적인 의견들은 기초신경학 통합강의 성적이 우수한 학생과 보통이하인 학생들 사이에 유의한 차이를 보이지 않았으나 (${\chi}^2$ 검증 결과), 성적이 우수한 학생일수록 가상강의의 효율성에 대해 긍정적이라는 경향은 알 수 있었다(Spearman 등위상관계수를 산출한 결과). 본 연구결과를 통해 제시된 개선방안과 축적된 경험을 바탕으로 점차 가상강의의 비중을 높이고 강의교수들 간의 유기적 협조가 이루어진다면 가상강의는 향후 기초의학 통합강의 운영의 새로운 패러다임(paradigm)이 될 것으로 사료된다.

• Investigative Magnetic Resonance Imaging
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• v.20 no.1
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• pp.53-60
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• 2016

Purpose: To develop a technique for quantifying the $^{13}C$-metabolites by performing frequency-selective hyperpolarized $^{13}C$ magnetic resonance spectroscopy (MRS) in vitro which combines simple spectrally-selective excitation with spectrally interleaved acquisition. Methods: Numerical simulations were performed with varying noise level and $K_p$ values to compare the quantification accuracies of the proposed and the conventional methods. For in vitro experiments, a spectrally-selective excitation scheme was enabled by narrow-band radiofrequency (RF) excitation pulse implemented into a free-induction decay chemical shift imaging (FIDCSI) sequence. Experiments with LDH / NADH enzyme mixture were performed to validate the effectiveness of the proposed acquisition method. Also, a modified two-site exchange model was formulated for metabolism kinetics quantification with the proposed method. Results: From the simulation results, significant increase of the lactate peak signal to noise ratio (PSNR) was observed. Also, the quantified $K_p$ value from the dynamic curves were more accurate in the case of the proposed acquisition method compared to the conventional non-selective excitation scheme. In vitro experiment results were in good agreement with the simulation results, also displaying increased PSNR for lactate. Fitting results using the modified two-site exchange model also showed expected results in agreement with the simulations. Conclusion: A method for accurate quantification of hyperpolarized pyruvate and the downstream product focused on in vitro experiment was described. By using a narrow-band RF excitation pulse with alternating acquisition, different resonances were selectively excited with a different flip angle for increased PSNR while the hyperpolarized magnetization of the substrate can be minimally perturbed with a low flip angle. Baseline signals from neighboring resonances can be effectively suppressed to accurately quantify the metabolism kinetics.