• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1994년도 춘계학술대회논문집
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• pp.32-37
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• 1994

This paper surveys the various methodologies for the objective measurement of visual fatigue. Visual fatigue is a psychophysiological symtom caused by the excessive use of eyes and it can be used as an important measure of the effectiveness and the safety of visual displays. The purpose of this paper is to compare the various visual fatigue measurement methodologies in a sense of the suitability for the ergonomic research. The measurement methodologies based on accommodation, convergence, visual evoked potential, eye movement, eye blinking, and flicker fusion were discussed and compared.

• 대한의용생체공학회:의공학회지
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• 제29권6호
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• pp.477-483
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• 2008

The observations of difference and similarity in brain activities involved in processing different languages have fundamental importance in cognitive neuroscience. The purpose of this study was to investigate the difference and similarity in temporal brain activation patterns due to the language difference during visual perception of Korean and English words under priming. Especially, we tried to find the difference in evoked spectral power in gamma-band, which is known to reflect feature binding. The stimulation was visually presented as word pairs belonging to same or different categories so that N400 event-related potential(ERP) was evoked. Average ERP analysis and spectral analysis of gamma-band activity(GBA) were performed on 12 normal Korean subjects. Several ERP components such as P1, N1, N400, and P600 could be identified consistently, and the differences in N1, N400, and P600 were observed. From the spectral analysis, we found that the evoked GBA(eGBA) was significantly larger for English at ${\sim}100$ ms poststimulus. The latency of the eGBA was also considerably delayed for English. Overall, the results on the ERP components and eGBA analyses seem to be commensurate with subjects' familiarity of each language, and the difficulty of perceiving words of each language. The methods of this study can also be applied for clinical purposes considering that the language-related processing can be greatly altered for the patients with neurological or psychiatric diseases.

• 대한의용생체공학회:의공학회지
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• 제30권4호
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• pp.347-354
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• 2009

For the reliable transmission of meaningful visual information using prosthetic electrical stimulation, it is required to develop an effective stimulation strategy for the generation of electrical pulse trains based on input visual information. The characteristics of neuronal activities of retinal ganglion cells (RGCs) evoked by electrical stimulation should be understood for this purpose. In this study, for the development of an optimal stimulation strategy for visual prosthesis, we analyzed the neuronal responses of RGCs in rd1 mouse, photoreceptor-degenerated retina of animal model of retinal diseases (retinitis pigmentosa). Based on the in-vitro model of epiretinal prosthesis which consists of planar multielectrode array (MEA) and retinal patch, we recorded and analyzed multiunit RGC activities evoked by amplitude-modulated electrical pulse trains. Two modes of responses were observed. Short-latency responses occurring at 3 ms after the stimulation were estimated to be from direct stimulation of RGCs. Long-latency responses were also observed mainly at 2 - 100 ms after stimulation and showed rhythmic firing with same frequency as the oscillatory background field potential. The long-latency responses could be modulated by pulse amplitude and duration. From the results, we expect that optimal stimulation conditions such as pulse amplitude and pulse duration can be determined for the successful transmission of visual information by electrical stimulation.

• 한국안광학회지
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• 제7권1호
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• pp.51-55
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• 2002

본 연구는 정상 시력을 가진 피검자의 안구가 동향운동을 하도록 주시점의 위치를 변경하며, 동향운동이 대뇌 시 피질 cerebral visual cortex의 뇌파에 미치는 영향을 분석하였다. 시 유발전위 장치(visual evoked potential system)는 Bio-Pag(production in USA)을 이용하였으며, 검사결과는 컴퓨터에 입력하여 분석하였다. 검사실의 조도는 50lux이며, 사용한 시표의 직경은 3 cm의 붉은 광점이며, 우전 dextroversion과 좌전 levoversion에 따른 결과는 다음과 같다. 1. 시자극에 관계하는 시 피질의 뇌파 출현의 높은 빈도는 delta wave, beta wave, theta wave 그리고 alpha wave의 순으로 나타났다. 2. 우전과 좌전에 대한 뇌파의 종류와 진폭은 거의 비슷하다. 3. 진폭에 대한 히스토그램은 우전과 좌전 모두 가우시안 Gausian 분포로 나타났다. 4. 뇌파의 진폭에 대한 위상 분석의 결과는 거의 비슷하다. 5. 뇌파 진폭과 주파수에 대한 fast fourier transform 분석에서 대개 20 Hz 이하의 저주파 low frequency로 나타났으며, 우전과 좌전의 결과는 비슷하다.

• 대한수의학회지
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• 제53권4호
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• pp.265-267
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• 2013

A 3-month-old, intact male French bulldog was suspected of deafness. The dog was irresponsive to environmental noises generated out of sight, but normal responses were noted for visual stimuli. No abnormalities were observed on the neurological, otoscopic, radiographic, and blood examinations. To diagnose the apparent deafness, brainstem auditory evoked potential (BAEP) was recorded in the presented dog together with a normal dog. While the BAEP from the control dog showed a normal wave consisting of 5 peaks, absence of all peaks was noted in the suspected deaf dog. Therefore the dog was definitively diagnosed as bilaterally congenital sensorineural deafness.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 추계학술대회
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• pp.86-89
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• 1995

A clinically oriented 32 channel Electroencephalogram (EEG) and evoked potential (EP) mapping system has been developed. The EEG and EP signals acquired from 32-channel electrodes are amplified by the pre-amplifier located near patient and are then tither amplified by main amplifier. An automatic artifact rejection scheme is employed using a neural network by which examination time is reduced substantially. Auditary and visual stimuli are used for the evoked potential mapping. A user-friendly graphical interface based on the Microsoft Window 3.1 is developed for the operation of the system. Statistical databases for the poop and individual comparisons are also included to support statistically based diagnosis.

• 대한임상검사과학회지
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• 제51권2호
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• pp.198-204
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• 2019

여러가지 약물에도 발작의 증세가 조절되지 않는 난치성 뇌전증 환자에서 다양한 치료법들을 시도해 볼 수 있다. 하지만 그 중 수술적인 방법이 필요한 환자에서는 수술 전 검사를 통해 발작부위의 절제부분을 결정한다. 정확한 병변의 측정과 안전한 수술을 위해 뇌 피질에 전극 삽입술을 시행한다. 피질에 삽입된 전극으로 단순히 뇌파만을 기록하는 것이 아니라 다양한 검사를 시도해 그 부위가 갖는 기능을 확인할 수 있고 그런 검사법 중 하나로 유발전위 검사법이 있다. 2015년 1월부터 2018년 12월까지 70명의 환자를 대상으로 측정된 파형의 경향이 의미하는 바를 분석하였다. 뇌 피질에 삽입된 전극에서 기록된 체성감각유발전위는 중심고랑의 주행경로를 찾아 일차운동영역 및 일차감각영역을 피해 수술 할 수 있다. 또한 청각유발전위와 시각유발전위를 이용해 청각피질과 시각피질에서 기능적 피질의 확인과 뇌파검사상 나타난 발작초점부위와의 관계를 비교해 절제부위를 결정하는데 도움을 주고 수술 후에 발생할 수 있는 기능적 장애를 최소화 할 수 있다.

• 전자공학회논문지
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• 제50권11호
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• pp.195-205
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• 2013

집중에 관한 뇌파 해석은 인간의 인지 이해에 기본적인 요소이다. 본 연구에서는 시각자극에 대한 뇌의 집중, 비집중 상태의 차이특성을 비선형 분석하였다. 적은 샘플 데이터와 시간에 따른 변화특성을 해석하기 위하여 반복 정량 분석 법을 사용하였으며, 자극에 동기된 유발 전위의 반복궤적, 색상 반복 궤적을 도식화하였으며, 비선형 특징 파라미터들의 평균특징과 시변 특성을 추출하였다. 집중-비집중 도식과 파라미터 쌍은 위상공간 변환의 차원과 시간 지연을 결정하기 위한 정보를 제공하였으며, 집중 시의 뇌가 비집중 시의 뇌보다 복잡하다는 특징을 보였으며, 자극에 동기된 유발전위는 평균적 의미에서 동일 반응을 보이나 국부적으로는 환경과 상태에 따라 변화하였다. 본 실험을 통하여 시각자극에 대한 집중과 비집중 시 뇌의 비선형 현상을 해석하기 위한 가능성을 확인하였다.

• Annals of Clinical Neurophysiology
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• 제8권2호
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• pp.199-202
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• 2006

We report a case of chiasmal optic neuritis in a patient who had been diagnosed as multiple sclerosis, and was presented with bitemporal hemianopsia. The brain MRI revealed a high signal lesion with focal enhancement in optic chiasm, and the visual evoked potential functionally supported it. This is the first case of chiasmal optic neuritis in multiple sclerosis with temporally and spatially disseminated lesions.

• 대한의용생체공학회:의공학회지
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• 제39권1호
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• pp.16-21
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• 2018

In this study, we investigated the activity of Mirror Neuron System(MNS) and Steady State Visual Evoked Potential(SSVEP) according to frequency and duty rate of the flickering action video. Eight subjects were recruited for this study. The stimulus was consisted of a three-minute black and a flickering action video and they were repeatedly presented every six seconds. We used 50%, 75% of duty rate for each frequency 7.5 Hz and 15 Hz, and we also used the non-flickering condition and rest condition. As a result, the Mu suppression was the largest at 7. 5Hz and 50% duty rate and the SSVEP power was higher at 15 Hz than 7.5 Hz.