• Journal of Korea Multimedia Society
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• v.19 no.8
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• pp.1260-1274
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• 2016

To obtain good summarization algorithms, we need first understand how people summarize videos. 'Semantic gap' refers to the gap between semantics implied in video summarization algorithms and what people actually infer from watching videos. We hypothesized that ERP responses to real time videos will show either N400 effects to topic-irrelevant shots in the 300∼500ms time-range after stimulus on-set or P600 effects to topic-relevant shots in the 500∼700ms time range. We recruited 32 participants in the EEG experiment, asking them to focus on the topic of short videos and to memorize relevant shots to the topic of the video. After analysing real time videos based on the participants' rating information, we obtained the following t-test result, showing N400 effects on PF1, F7, F3, C3, Cz, T7, and FT7 positions on the left and central hemisphere, and P600 effects on PF1, C3, Cz, and FCz on the left and central hemisphere and C4, FC4, P8, and TP8 on the right. A further 3-way MANOVA test with repeated measures of topic-relevance, hemisphere, and electrode positions showed significant interaction effects, implying that the left hemisphere at central, frontal, and pre-frontal positions were sensitive in detecting topic-relevant shots while watching real time videos.

• Journal of Korean Neurosurgical Society
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• v.64 no.2
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• pp.282-288
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• 2021

Objective : Electrooculography (EOG) records eyeball movements as changes in the potential difference between the negatively charged retina and the positively charged cornea. We aimed to investigate whether reliable EOG waveforms can be evoked by electrical stimulation of the oculomotor and abducens nerves during skull base surgery. Methods : We retrospectively reviewed the records of 18 patients who had undergone a skull base tumor surgery using EOG (11 craniotomies and seven endonasal endoscopic surgeries). Stimulation was performed at 5 Hz with a stimulus duration of 200 μs and an intensity of 0.1-5 mA using a concentric bipolar probe. Recording electrodes were placed on the upper (active) and lower (reference) eyelids, and on the outer corners of both eyes; the active electrode was placed on the contralateral side. Results : Reproducibly triggered EOG waveforms were observed in all cases. Electrical stimulation of cranial nerves (CNs) III and VI elicited positive waveforms and negative waveforms, respectively, in the horizontal recording. The median latencies were 3.1 and 0.5 ms for craniotomies and endonasal endoscopic surgeries, respectively (p=0.007). Additionally, the median amplitudes were 33.7 and 46.4 μV for craniotomies and endonasal endoscopic surgeries, respectively (p=0.40). Conclusion : This study showed reliably triggered EOG waveforms with stimulation of CNs III and VI during skull base surgery. The latency was different according to the point of stimulation and thus predictable. As EOG is noninvasive and relatively easy to perform, it can be used to identify the ocular motor nerves during surgeries as an alternative of electromyography.

• Korean Journal of Clinical Laboratory Science
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• v.54 no.2
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• pp.157-162
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• 2022

The purpose of the direct cortical and subcortical stimulation technique is to prevent false positives caused by transcranial electrical motor evoked potentials (TceMEP) in surgery on patients with brain tumors that have occurred around the motor cortex and to preserve the correct mapping of motor areas during surgery and the corticospinal tract. In addition, it reduces the trial and error that occurs during the intraoperative neurophysiological monitoring (INM) process and minimizes the test time, so that accurate information is communicated to the surgeon with quick feedback on the test results. The most important factors of this technique are, first, examination at a stimulus threshold of a certain intensity, and second, maintaining anesthesia depth at an appropriate level to prevent false positives from occurring during surgery. The third is the installation of a multi-level channel recording electrode on the opposite side of the area of operation to measure the TceMEP waveform and the response to direct cortical and subcortical stimulation in as many muscles as possible. If these conditions are maintained, it is possible to predict causes that may occur in other factors, not false positives, from the INM test.

• The Korean Journal of Physiology and Pharmacology
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• v.27 no.6
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• pp.541-553
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• 2023

Retinal prostheses have shown some clinical success in restoring vision in patients with retinitis pigmentosa. However, the post-implantation visual acuity does not exceed that of legal blindness. The reason for the poor visual acuity might be that (1) degenerate retinal ganglion cells (RGCs) are less responsive to electrical stimulation than normal RGCs, and (2) electrically-evoked RGC spikes show a more widespread not focal response. The single-biphasic pulse electrical stimulation, commonly used in artificial vision, has limitations in addressing these issues. In this study, we propose the benefit of multiple consecutive-biphasic pulse stimulation. We used C57BL/6J mice and C3H/HeJ (rd1) mice for the normal retina and retinal degeneration model. An 8 × 8 multi-electrode array was used to record electrically-evoked RGC spikes. We compared RGC responses when increasing the amplitude of a single biphasic pulse versus increasing the number of consecutive biphasic pulses at the same stimulus charge. Increasing the amplitude of a single biphasic pulse induced more RGC spike firing while the spatial resolution of RGC populations decreased. For multiple consecutive-biphasic pulse stimulation, RGC firing increased as the number of pulses increased, and the spatial resolution of RGC populations was well preserved even up to 5 pulses. Multiple consecutive-biphasic pulse stimulation using two or three pulses in degenerate retinas induced as much RGC spike firing as in normal retinas. These findings suggest that the newly proposed multiple consecutive-biphasic pulse stimulation can improve the visual acuity in prosthesis-implanted patients.

• Progress in Medical Physics
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• v.19 no.1
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• pp.73-79
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• 2008

Retinal prosthesis is regarded as the most feasible method for the blind caused by retinal diseases such as retinitis pigmentosa (RP) or age related macular degeneration (AMD). Recently Korean consortium launched for developing retinal prosthesis. One of the prerequisites for the success of retinal prosthesis is the optimization of the electrical stimuli applied through the prosthesis. Since electrical characteristics of degenerate retina are expected to differ from those of normal retina, we performed voltage stimulation experiment both in normal and degenerate retina to provide a guideline for the optimization of electrical stimulation for the upcoming prosthesis. After isolation of retina, retinal patch was attached with the ganglion cell side facing the surface of microelectrode arrays (MEA). $8{\times}8$ grid layout MEA (electrode diameter: $30{\mu}m$, electrode spacing: $200{\mu}m$, and impedance: $50k{\Omega}$ at 1 kHz) was used to record in-vitro retinal ganglion cell activity. Mono-polar electrical stimulation was applied through one of the 60 MEA channel, and the remaining channels were used for recording. The electrical stimulus was a constant voltage, charge-balanced biphasic, anodic-first square wave pulse without interphase delay, and 50 trains of pulse was applied with a period of 2 sec. Different electrical stimuli were applied. First, pulse amplitude was varied (voltage: $0.5{\sim}3.0V$). Second, pulse duration was varied $(100{\sim}1,200{\mu}s)$. Evoked responses were analyzed by PSTH from averaged data with 50 trials. Charge density was calculated with Ohm's and Coulomb's law. In normal retina, by varying the pulse amplitude from 0.5 to 3V with fixed duration of $500{\mu}s$, the threshold level for reliable ganglion cell response was found at 1.5V. The calculated threshold of charge density was $2.123mC/cm^2$. By varying the pulse duration from 100 to $1,200{\mu}s$ with fixed amplitude of 2V, the threshold level was found at $300{\mu}s$. The calculated threhold of charge density was $1.698mC/cm^2$. Even after the block of ON-pathway with L-(1)-2-amino-4-phosphonobutyric acid (APB), electrical stimulus evoked ganglion cell activities. In this APB-induced degenerate retina, by varying the pulse duration from 100 to $1200{\mu}s$ with fixed voltage of 2 V, the threshold level was found at $300{\mu}s$, which is the same with normal retina. More experiment with APB-induced degenerate retina is needed to make a clear comparison of threshold of charge density between normal and degenerate retina.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.12 no.1
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• pp.25-50
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• 2001

Using Fourier transformation and wavelet analysis, we compared the auditory event-related potentials of the patients with attention deficit-hyperactivity disorders(abbr. ADHD, 13 boys) and normal control children(8 boys). Amplitudes of the event-related potentials which were calculated via Fourier transformation were compared between the groups and between conditions(non-target versus target) in each group. To the non-target stimuli, the patients with ADHD showed significantly greater amplitudes across almost all of the electrode sites and frequencies. To the target stimuli, the incidents which ADHD patients showed much higher amplitudes than normal controls significantly decreased, while those of the reverse results increased significantly. These results were consistent with the comparison results about negative difference wave(abbr. Nd wave) using Fourier transformation. In summary, it was proved that non-target stimulus which should be ignored elicited more robust electrical response from the patients with ADHD than normal children, but the target stimulus which reguired active processing did much less electrical activity in the patients. For the patients, they showed much inhibited electrical response to the target stimuli in some electrodes and frequency ranges. Normal children were more strongly stimulated by the target stimuli in almost all electrodes and frequency ranges than the patients, but less in prefrontal leads and frontal leads. Wavelet analysis results proved that early responses(0-300msec) to the nontarget stimuli of the patients were significantly greater than the normal controls in prefrontal, anterior frontal, some parts of temporal, and occipital lobes and that late response(300-370msec) were significantly lesser than normal children in parietal and central electrodes. Target stimuli elicited significantly higher electrical activity in both group than non-target stimuli did. Prefrontal and frontal lobes showed stronger responses in the patients than normal children irrespective of stimulus condition, but parietal and temporal lobes did higher activities in normal children than the patients only to the target stimuli. In conclusion, the patients with ADHD showed much greater responses to the stimuli which should be ignored, but failed to activated the necessary processes to the target stimuli. Also, we found that the frequency-dimension analysis and wavelet analysis were useful for the signal processing such as event related potentials.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.217-225
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• 2002

The authors examined the response of electrocardiogram(ECG) of Nile tilapia, Oreochromis niloticus [Linnaeus] to light stimuli. The experiments were performed in such a way that three levels of light stimuli(10, 100 and 400 lu$\chi$) were given to fishes with an electrode inserted into their bodies and then their ECGs were recorded continuously for 60 minutes in 16~18$^{\circ}C$. The results which are divided into by day and by night and then analyzed by fishes' conditions are as follows; 1. Nile tilapias reached a stable condition 3 minutes after anesthesia. In stable condition, the heart rate average was 47.6beat/min by day and 45.1beat/min by night. And the action potential average was 1.0.4$mutextrm{V}$ by day and 1.24$mutextrm{V}$ by night. 2. The heart rate average by three levels of light stimuli was, \circled1 In stimulus condition, in case of 10 lu$\chi$ 39.7beat/min by day and 38.2beat/min by night, in case of 100 lu $\chi$8.7beat/min by day and 36.9beat/min by night, and in case of 40.0. lux 36.8 beat/min by day and 35.8beat/min by night. \circled2 In recovery condition, in case of 10 lu$\chi$ 47.1beat/min by day and 46.0beat/min by night, in case of 100 lu$\chi$ 47.2beat/min by day and 45.6 beat/min by night, and in case of 400 lu$\chi$ 48.1beat/min by day and 46.6beat/min by night. 3. The action potential average by three levels of light stimuli was, \circled1 In stimulus condition, in case of 10 lu$\chi$ 1.22$mutextrm{V}$ by day and 0.71$mutextrm{V}$ by night, in case of 100 lu$\chi$ 0..63$mutextrm{V}$ by day and 0.90$mutextrm{V}$ by night, and in case of 400 lu$\chi$ 1.39$mutextrm{V}$ by day and 1.63$mutextrm{V}$ by night \circled2 In recovery condition, in case of 10 lu$\chi$ 1.26$mutextrm{V}$ by day and 1.59$mutextrm{V}$ by night, in case of 100 lu$\chi$ 2.63$mutextrm{V}$ by day and 3.65$mutextrm{V}$ by night, and in case of 400. lu$\chi$ 2.52$mutextrm{V}$ by day and 3.67$mutextrm{V}$ by night.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.124-132
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• 2001

The authors examined the response of electrocardiogram (ECG) of Mirror carp, Cyprinus carpio [Linnaeus] to light stimuli. The experiments were performed in such a way that three levels of light stimuli (10, 100, and 400 lux) were given to fishes with an electrode inserted into their bodies and then their ECGs were recorded continuously for 60 minutes. The results which are divided into by day and by night and then analyzed by fishes conditions are as follows : 1. Mirror carps reached a stable condition 5 minutes after anesthesia. In this condition, the average heart rate was 64.9 beat/min by day and 65.3 beat/min by night. And the average action potential was 36.9 nV by day and 32.9 nV by night. 2. The average heart rate by three levels of light stimuli was, 1) In a stimulus condition, in case of 10 lux 68.7 beat/min by day and 46.0 beat/min by night, in case of 100 lux 53.4 beat/min by day and 44.1 beat/min by night, and in case of 400 lux 53.2 beat/min by day and 40.1 beat/min by night. 2) In a recovery condition, in case of 10 lux 67.9 beat/min by day and 57.2 beat/min by night, in case of 100 lux 68.8 beat/min by day and 61.0 beat/min by night, and in case of 400 lux 69.6 beat/min by day and 63.6 beat/min by night. 3. The average action potential by three levels of light stimuli was, 1) In a stimulus condition, in case of 10 lux 59.1 nV by day and 24.0 nV by night, in case of 100 lux 26.8 nV by day and 45.6 nV by night, and in case of 400 lux 71.7 nV by day and 14.4 nV by night. 2) In a recovery condition, in case of 10 lux 38.8 nV by day and 27.3 nV by night, in case of 100 lux 29.0 nV by day and 39.3 nV by night, and in case of 400 lux 66.4 nV by day and 21.4 nV by night.

• Journal of Chest Surgery
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• v.32 no.5
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• pp.428-432
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• 1999

Background: It has been shown that low-grade electrical stimulus can transform fatigue resistant muscles which then can be used to protect the heart. The bulky and cumbersome power sources of the artificial heart or implantable ventricular assist devices are still in need of solution; however, on the other hand, the implantable ventricular assist devices using the resistant muscles as the power source have the advantages of using its own muscle contractions. The purpose of this study was to determine the possibility of a clinical application of the skeletal muscle ventricle. Material and Method: Latissimus dorsi muscles (LDM) of 8 canines were used for skeletal muscle ventricle. A latex chamber was wrapped one and a half times with LDM. The chamber was attached to a pressure transducer via Tygon tube. An electrode stimulator was placed around the thoracodorsal nerve and LDM was stimulated in cyclic bursts of 0.31 sec on time and 6.0 sec off time using 3.0 volt Itrel stimulator. The preload volume was added to the system in 25cc increments. Ejection volumes, pressures, and peak power outputs were measured. Result: Ejection volume was 76.3cc with 0cc of preload. Ejection volumes were less than 70ml with increments of preload over 75cc Pressures were more than 107 mmHg when the preloads were less than 75cc and less than 100 mmHg when the preloads were more than 100cc. Peak power output of 16.6 W/kg was observed at 50cc preload. Conclusion: Depending on the changes of preload, the volumes ejected from skeletal muscle ventricle and pressures from the skeletal muscle contraction surpassed those of the normal heart. These data suggest that there are clinical applications for skeletal muscle ventricular assist system.

• Journal of KIISE:Software and Applications
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• v.29 no.11
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• pp.837-850
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• 2002

In this paper, we propose an EEG-based response time prediction method during a yes/no cognitive decision task. In the experimental task, a subject goes through responding of visual stimulus, understanding the given problem, controlling hand motions, and hitting a key. Considering the subject's varying brain activities, we model subjects' mental states with defining CT (cut time), ST (selection time), and RP (repeated period). Based on the assumption between ST and RT in the mental model, we predict subjects' response time by detection of selection time. To recognize the subjects' selection time ST, we extract 3 types of feature from the filtered brain waves at frequency bands of $\alpha$, $\beta$, ${\gamma}$ waves in 4 electrode pairs combined by spatial relationships. From the extracted features, we construct specific rules for each subject and meta rules including common factors in all subjects. Applying the ST detection rules to 8 subjects gives 83% success rates and also shows that the subjects will hit a key in 0.73 seconds after ST detected. To validate the detection rules and parameters, we test the rules for 2 subjects among 8 and discuss about the experimental results. We expect that the proposed detection method can be a basic technology for brain-computer-interface by combining with left/right hand movement or yes/no discrimination methods.