• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.131-133
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• 2000

In this paper, we proposed a new method for localizing the independent sources generating the observed EEG based on independent component analysis (ICA). The performance of the algorithm was tested through computer simulations.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.12a
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• pp.305-308
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• 2002

패턴 인식(Patterns Recognition)은 인공 지능의 한 분야로서 이해할 수 있는데, 요즈음은 보안과 관련하여 많은 연구가 진행되고 있다. 웨이블렛 변환(Wavelet Transform)은 공간-주파수 영역에서 신호의 국소화를 효율적으로 구현할 수 있다. 하지만, 이를 패턴 인식의 특징 추출에 그대로 이용할 경우 입력 신호의 위치 이동 등이 문제가 되며, 이것은 또한 에러 요인이 된다. 본 논문에서는 웨이블렛 변환을 패턴 인식에 적용할 경우 발생하는 입력 신호의 위치이동에 따른 문제점을 보완하여, 개선된 방법으로 패턴 인식에 사용할 수 있는 알고리즘을 제안하며, 실험 결과를 바탕으로 그의 타당성을 보인다.

• Korean Journal of Biological Psychiatry
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• v.22 no.2
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• pp.87-94
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• 2015

Objectives The power spectral analysis of electroencephalogram has been widely used to reveal the pathophysiology of the alcoholic brain. However, the results were not consistent and the three dimensional study can be hardly found. The purpose of this study was to investigate characteristics of the three dimensional electroencephalographic (EEG) activity of alcohol dependent patients using standardized low resolution electromagnetic tomography (sLORETA). Methods The participants consisted of 30 alcohol dependent patients and 30 normal healthy controls. All the participants were males who had refrained from alcohol at least one month and were not taking any medications. Thirty two channel EEG data was collected in the resting state with eyes-closed condition during 30 seconds. The three dimensional data was compared between two groups using sLORETA for delta, theta, alpha, beta1, beta2, and beta3 frequency bands. Results sLORETA revealed significantly increased brain cortical activity in alpha, beta1, beta2, and beta3 bands each in alcohol dependent patients compared to normal controls. The voxels showing the maximum significance were in the left transverse temporal gyrus, left superior temporal gyrus, left anterior cingulate, and left fusiform gyrus in alpha, beta1, beta2, and beta3 bands respectively. Conclusions These results suggest that chronic alcohol intake may cause neurophysiological changes in cerebral activity. Therefore, the measuring of EEG can be helpful in understanding the pathophysiology of cognitive impairements in alcohol dependence.

• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.124-126
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• 2000

The Minimum-Norm Least-Square(MNLS) approach based on lead field theory is an useful method to find an unique inverse solution for the measured magnetic field. The lead field depends on head geometry and location of sources and sensors. So, optimization of sensor array location is important issue for MNLS estimation. In this paper, we present an investigation for the optimization of sensor array location in computer simulation.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2758-2760
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• 2002

패턴 인식(Patterns Recognition)은 인공 지능의 한 분야로서 이해할 수 있는데, 요즈음은 보안과 관련하여 많은 연구가 진행되고 있다. 웨이블렛 변환(Wavelet Transform)은 푸리에 변환에 기반을 둔 기존의 알고리즘에 비해 시간-주파수 영역에서 신호의 국소화를 효율적으로 구현할 수 있다. 하지만, 이를 패턴 인식의 특징 추출에 그대로 이용할 경우 입력 신호의 위치 이동 등이 문제가 되며, 이것은 또한 에러 요인이 된다. 본 연구에서는 웨이블렛 변환을 패턴 인식에 적용할 경우, 입력 신호의 위치 이동 등이 있는 경우 생기는 문제점을 보완하여, 개선된 방법으로 패턴 인식에 사용할 수 있는 알고리즘을 제안하며, 실험 결과를 토대로 그의 타당성을 보인다.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2006.06a
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• pp.61-65
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• 2006

본 연구는 한국어 어휘중의성 해결과정에 관련된 대뇌활동을 살펴보기 위하여 MEG(magnetoencephalography)를 이용한 실험을 실시하였다. 일차적으로 기존의 중의성 관련 fMRI 실험 결과들이 MEG를 이용한 신호원 국소화 결과와 유사한 패턴을 보이는지 확인하였고, 본 실험의 주요 목적인 중의성 관련 처리과정에 기저하는 하위 처리과정이 어떠한 기능적 처리 요소들로 분해될 수 있는 지에 대해서도 시간 해상도가 높은 MEG의 특성을 이용하여 관찰하였다. 분석 결과, 한국어 중의어 해소과정의 하위처리 과정은 어휘의미 접속이라는 기본적인 과정 비에, 이들의 의미분지를 유발하는 단서의 유무가 그 활성화 영역의 시간적인 패턴과 중의성 해결을 위한 지속시간에 영향을 미치는 것으로 확인되었다.

• Korean Journal of Cognitive Science
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• v.28 no.1
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• pp.1-26
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• 2017

This study investigated the cortical generators of P300 in college students with schizotypal traits by using an auditory oddball paradigm, event-related potentials (ERPs) and standardized low resolution brain electromagnetic tomography (sLORETA) model. We also investigated the relationship between the current density of P300 and the clinical symptoms of schizophrenia. Based on the scores of Schizotypal Personality Questionnaire(SPQ), schizotypal trait (n=37) and control (n=42) groups were selected. For the measurement of P300, an auditory oddball paradigm, in which frequent standard tones (1000Hz) and rare target tones (1500Hz) were presented randomly, was used. Participants were required to count the number of the target tones during the task and report this at the end of the experiment. The two groups did not differ significantly in the accuracy of the oddball task. The schizotypal trait group showed significantly smaller P300 amplitudes than control group. In terms of source localization, both groups showed the P300 current density over bilateral frontal, parietal, temporal and occipital lobes. However, the schizotypal trait group showed significantly reduced activations in the left superior temporal gyrus and the right middle temporal gyrus, but increased activations in both left inferior frontal gyrus and right superior frontal gyrus compared to the control group. Furthermore, a negative correlation between the current density of the right superior frontal gyrus and SPQ disorganization score was found in the schizotypal trait group. These findings indicate that the individuals with schizotypal traits have dysfunctions of frontal and temporal areas, which are known to be the source of P300, as observed in patients with schizophrenia. In addition, the present results indicate that the disorganization score, rather than total score, of the SPQ is useful in predicting the risk of future schizophrenia.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.97-102
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• 2003

Multi-channel images of 11-MUA(11-Mercaptoundecanoic acid) and 11-MUOH(11-Mercaptoundecanol) self-assembled monolayers were obtained by using two-dimensional surface plasmon resonance (SPR) absorption. The patterning process was simplified by exploiting direct photo-oxidation of thiol bonding (photolysis) instead of conventional photolithography. Sharper images were resolved by using a white light source in combination with a narrow bandpass filter in the visible region, minimizing the diffraction patterns on the images. The line profile calibration of the image contrast caused by different resonance conditions at each point on the sensor surface (at a fixed incident angle) enables us to discriminate the monolayer thickness in nanometer scale. Furthermore, there is no signal degradation such as photo bleaching or quenching, which are common in the detection methods based on fluorescence.

• Science of Emotion and Sensibility
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• v.8 no.4
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• pp.403-413
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• 2005

The purpose of the present study was to investigate the responses to positive/negative emotional stimuli for the different sensitivities of behavioral activation system (BAS) and behavioral inhibition system (BIS). We recorded If-channel EEG data for 8 BAS sensitive subjects an48 BIS sensitive subjects. EEGs were analyzed with LORETA (Low-resolution electromagnetic tomography) From scalp-recorded electrical potential distribution, LORETA computes the three-dimensional intracerebral distributions of current density for specified EEG frequency bands. hs results , significant differences between the BAS sensitive group ant the BIS sensitive group appeared LORETA alpha activities over the prefrontal lobe and the cingulate gyrus. Prefrontal regions and limbic system including cingulate gyrus are involved in emotional processing. Moreover, subjects with the high BAS sensitivity. responded more sensitively to the positive stimulation than subjects with the high BIS sensitivity. Therefore, our results suggest the possibility of correlation between BAS/BIS sensitivity and positive/negative emotional stimuli.

• Korean Journal of Biological Psychiatry
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• v.10 no.2
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• pp.168-176
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• 2003

Objectives:We investigated the characteristics of P300 generators in obsessive-compulsive disorder(OCD) patients by using voxel-based statistical parametric mapping of current density images. Methods:P300 generators, produced by a rare target tone of 1500Hz under a frequent non-target tone of 1,000Hz, were measured in 15 right-handed OCD patients and 15 controls. Low Resolution Electromagnetic Tomography(LORETA), using a realistic head model of the boundary element method based on individual MRI, was applied to the 128-channel EEG. Statistical parametric mapping(SPM) was applied for the statistical analysis. Results:We found that both groups had the mean current density of P300 in the parietal, temporal and prefrontal lobe. There was a trend for decreased current density in the prefrontal area in OCD patients. The statistical comparison showed current density increase in the supraparietal area, a statistically significant longer P300 latency and a trend for reduced P300 amplitude in OCD patients. Conclusion:It suggests that P300 source of both groups exists in multiple brain regions at the same time. And both groups had no statistically significant differences in the current density of P300 except for increased current density in the supraparietal area in OCD patients. But, considering the statistically significant longer P300 latency, a trend for reduced P300 amplitude and relative mean current density reduction in the prefrontal area in OCD patients, this study suggests that the frontal lobe may have a reduced normal inhibitory process in OCD patients.