• Korean Journal of Cognitive Science
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• v.19 no.1
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• pp.75-88
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• 2008

Visual scene contains lots of redundant information. To process this redundant information without increasing brain's volume, human visual system may summarize incoming information. If similar but different information are given to visual system, visual system extracts statistical properties of the information. One example of the statistical representation is representation of mean size. The mean representation is accurate and durable. The process of mean representation is suggested to be parallel. However, previous studies on the mean representation mostly used behavioral methods. The purpose of this study was to investigate which neural regions extracted the mean size of a set of circles using fMRI method. According to previous studies, BOLD signal of certain areas that were in charge of cousin stimuli decreased when the same stimuli presented repetitively. We used this paradigm and found that BOLD signal of right occipital area was decreased when same mean site was presented repeatedly. This results suggest that right occipital area is the locus of mean representation of visual stimuli.

• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1165-1170
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• 2023

In this study, we aimed to develop a cost-effective neuro-modulation device for use in neuroscientific and clinical medical imaging applications. To achieve this, we designed and fabricated a brain neuro-modulation device with a material cost of less than $500, and subsequently evaluated its performance. The measured performance was found to be comparable to existing medical devices (TENS), with the developed device being compact in size, measuring less than 3 cm by 3 cm. The outcomes of this study are expected to be applicable in accelerating research and development in related fields, as well as in the rapid commercialization of neuro-modulation technology. Furthermore, it is anticipated that this work will contribute to advancements in functional radiological medical imaging technology and enhance accessibility to brain science and brain stimulation technology.

• Annual Conference on Human and Language Technology
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• 2004.10d
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• pp.319-322
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• 2004

한글은 알파벳 문자처럼 소리를 바탕으로 한 표음문자이지만, 각 글자의 형태는 표의문자인 한자와 유사한 시각적인 효과를 제공한다. 본 연구에서는 자기공명 영상법을 이용하여 한국인이 한글문자와 그림을 인지할 경우 나타나는 신경망적 특성을 알아보았다. 그 결과. 한글과 그림 자극에 대하여 양반구 모두에서 후측두엽 부위의 활성화가 나타났다. 그러나, 전두엽과 측두엽 부분의 활성화는 오직 한글자극의 경우에만 관찰되었다. 좌반구 중전 두엽의 활성화는 음성 및 의미론적 처리와 관련되어 있다고 볼 수 있으며, 우반구 anterior cingulate 활성화는 언어 및 소리의 형성과 관계가 있다고 할 수 있다. 본 연구에서는 우반구 medial frontal 영역인 BA 8의 활성화가 관찰되었다 이 영역은 시각적으로 고차적인 비음성적 자극을 통제하거나 그와 유사한 시각공간적인 정보의 분석과 관련이 있다고 알려져 있다. 본 연구의 결과는 한글의 특성적인 형태가 특정 영역을 활성화시킨 것을 시사한다.

• Investigative Magnetic Resonance Imaging
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• v.17 no.3
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• pp.169-180
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• 2013

Purpose : The purpose of this study was to setup a concuurent transcranial magnetic stimulation (TMS)-functional MRI (fMRI) system for understanding causality of the functional brain network. Materials and Methods: We manufactured a TMS coil holder using nonmagnetic polyether ether ketone (PEEK). We simulated magnetic field distributions in the MR scanner according to TMS coil positions and angles. To minimize image distortions caused by TMS application, we controlled fMRI acquisition and TMS sequences to trigger TMS during inter-volume intervals. Results: Simulation showed that the magnetic field below the center of the coil was dramatically decreased with distance. Through the MR phantom study, we confirmed that TMS application around inter-volume acquisition time = 100 miliseconds reduced imaging distortion. Finally, the applicability of the concurrent TMS-fMRI was tested in preliminary studies with a healthy subject conducting a motor task within TMS-fMRI and passive motor movement induced by TMS in fMRI. Conclusion: In this study, we confirmed that the developed system allows use of TMS inside an fMRI system, which would contribute to the research of brain activation changes and causality in brain connectivity.

• Journal of Biomedical Engineering Research
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• v.22 no.6
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• pp.487-496
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• 2001

In this study, a galvanic stimulator providing bipolar mode controlled by a PIC(peripheral interface controller) was constructed to evaluate vestibular function The maximum load and maximum current intensity of the constant current source were 3$k\Omega$ and 5mA. respectively. and it could Produce DC, sine wavers. or Pulse waves. Eve movements of 20 normal subjects by galvanic stimulation were analyzed using a commercial videooculogragh. During stimulating with DC for 30 sec. we recorded the response of eye movement with current intensity of 0.75. 1 2, and 3 mA. Nystagmus occurred to all the subjects when the galvanic stimulus intensity was larger than 2 mA. Average SPV(slow Phase eye movement velocity) and the number of nystagmus increased from 7.1 to 4.8 deg/sec and from 17 to 48, respectively, when the stimulus current increased from 0.75 to 3 mA. All the fast eye movement of the nystagmus were the direction of the negative electrode. The asymmetry which means the difference between right- and left-eye movements decreased when the stimulus intensity increased. It is expected that this study would be useful in evaluating vestibular function and in studying basic Physiology mechanism of vestibular ocular reflex by galvanic stimulus .

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.11
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• pp.2143-2149
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• 2007

Visual Cortex Stimulator is among artificial retina prosthesis for blind man, is the method that stimulate the brain cell directly without processing the information from retina to visual cortex. In this paper, we propose image construction and recognition model that is similar to human visual processing by recognizing the feature data with orientation information, that is, the characteristics of visual cortex. Back propagation algorithm based on Delta-bar delta is used to recognize after extracting image feature by Kirsh edge detector. Various numerical patterns are used to analyze the performance of proposed method. In experiment, the proposed recognition model to extract image characteristics with the orientation of information from retinal cells to visual cortex makes a little difference in a recognition rate but shows that it is not sensitive in a variety of learning rates similar to human vision system.

• Investigative Magnetic Resonance Imaging
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• v.8 no.1
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• pp.9-16
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• 2004

Purpose : The purpose of this study was to assess supplementary motor area (SMA) activation during motor, sensory, word generation, listening comprehension, and working memory tasks using functional magnetic resonance imaging (fMRI). Materials and Methods : Sixteen healthy right-handed subjects (9M, 7F) were imaged on a Siemens 1.5T scanner. Whole brain functional maps were acquired using BOLD EPI sequences in the axial plane. Each paradigm consisted of five epochs of activation vs. the control condition. The activation tasks consisted of left finger complex movement, hot sensory stimulation of the left hand, word generation, listening comprehension, and working memory. The reference function was a boxcar waveform. Activation maps were thresholded at an uncorrected p=0.0001. The thresholded activation maps were placed into MNI space and the anatomic localization of activation within the SMA was compared across tasks. Results : SMA activation was observed in 16 volunteers for the motor task, 11 for the sensory task, 15 for the word generation task, 5 for the listening comprehension task, and 15 for the working memory task. The rostral aspects of the SMA showed activity during the word generation and working memory tasks, and the caudal aspects of the SMA showed activity during the motor and sensory tasks. Right (contralateral) SMA activation was observed during the motor and sensory tasks, and left SMA activation during the word generation and memory tasks. Conclusion : Our results suggest that SMA is involved in a variety of functional tasks including motor, sensory, word generation, and working memory. The results obtained also support the notion that functionally specific subregions exist within the region classically defined as the SMA.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.811-815
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• 2005

최근 선진 각국에서는 시각장애인을 위한 인공 망막 모델구현을 위한 연구가 매우 활발히 진행 중이다. 인공 망막의 여러 기법중 시각피질자극에 의한 방법은 망막손상과 시신경 손상 환자에게 적용할 수 있도록 시피질을 자극한다. 그러나 이 방법은 시각자극전달의 중간단계를 생략하고 직접 뇌세포를 자극하는 것이다. 따라서 본 논문에서는 시각피질자극방법에 기반하여 인간시각처리와 유사하게 영상의 압축방법을 부과함으로써 세포의 특성을 고려한 모델을 나타낸다. 실험 데이터로는 자동차 번호판 숫자들이며, 인식기는 SOM을 사용하였다. 실험결과, 제안된 인식모델과 일반적 인식모델과의 차이가 없음을 알 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3C
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• pp.217-223
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• 2012

In this paper, we would like to propose techniques to analyze effect according to stimulation kidney associated hand acupuncture by applying technique to measure changes of facial image and voice signal. To this end, we measured color change of JIGAK(jaw) area associated kidney in facial image and voice signal stimulation before and after of kidney associated hand acupuncture. In addition, we measured changes of the first formant frequency bandwidth and Shimmer to element of voice signal analysis in connection with kidney in experiment. We can be measured reduction of the first formant frequency bandwidth and Shimmer, black of JIGAK area according to stimulation of kidney associated hand acupuncture. Finally, we would like to demonstrate objective effect of kidney associated hand acupuncture through the analysis of statistical significance by measurement techniques of facial image and voice signal.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.11a
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• pp.373-376
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• 2005

본 연구에서는 뇌의 반응과 말초신경계의 변화를 통하여 유머와 기쁨의 긍정적인 정서의 구분이 가능한가를 밝히고자 하였다. fMRI와 말초신경계 반응 측정 실험 각각을 수행하는 동안, 유머와 기쁨정서를 유발하는 동영상 자극(2분)이 제시되었고, 실험이 끝난 후 심리적인 평가도 함께 수행되었다. fURI 실험은 boxcar design으로 한 session 내에 두 block으로 구성되었다. 말초신경계 반응실험에서는 안정상태와 정서상태에서의 피부전기 반응을 측정하였다. fMRI 결과, 유머자극과 기쁨자극 제시 시 공통적으로 precentral Cortex, temporal Cortex, precuneus 가 활성화 되었고, 유머자극은 기쁨자극에 비하여 우측 middle temporal cortex, 우측 inferior frontal cortex, 좌측 middle frontal cortex 에서 큰 활성화를 보였다. 피부전기 반응(EDA) 분석 결과 두 정서 모두 안정상태에 비하여 유의하게 증가하였고, 유머자극은 기쁨자극에 비하여 피부전도수준(SCL)과 피부전도반응의 수(NSCR)에서 유의하게 증가하는 것으로 나타났다.