• Journal of Biomedical Engineering Research
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• v.22 no.3
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• pp.259-267
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• 2001

The visual evoked potentials(VEPs) is used to assist in the diagnosis of specific disorders associated with involvement of the sensory visual pathways. The P100 latency is an important parameter which is diagnosis of optic nerve disorders. There are characteristics of latency delay, wave distortion, amplitude deduction in abnormal subjects. It is difficult to diagnose in the case of producing peak at the P100 latency. In this paper, difference of pattern between normal VEPs and abnormal VEPs using the Choi-Williams distribution method is studied. We observed the relationship about time and spectrum. The result shown that normal VEPs had maximum spectral value at 20Hz~26.7Hz and abnormal VEPs had maximum spectral value at 16.7Hz~20Hz. Also normal VEPs spectrum is higher than abnormal VEPs spectrum.

• Annals of Clinical Neurophysiology
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• v.2 no.1
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• pp.13-20
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• 2000

Background and Objective : Visual evoked potentials(VEPs) is considered to be a reliable diagnostic procedure for examining patients with anterior visual pathways. Some abnormalities in the recordings on monocular stimulation have been said to indicate retrochiasmal lesion, but less consistent results have been reported. This study is to evaluate the positive predictability of VEP for the detection of retrochiasmal lesion. Methods : We reviewed VEPs that could be interpreted as indicative of a retrochiasmal lesions, based on amplitude or latency asymmetry recorded on the left(O1) and right(O2) occipital regions. Bilateral absent VEPs on both recording(O1 and O2) without evidence of prechiasmal lesion were included. During 5 years, we identified 31 patients who met the above criteria and who had undergone magnetic resonance imaging(MRI) of brain(one patient underwent computerized tomography). Twenty three patients underwent pattern reversal VEPs and others underwent flash goggle VEPs. Results : Brain imagings were abnormal in 29 and were normal in 2. Of the 29 abnormal scans, lesions in posterior visual pathway were detected in 21 scans(predictive value=68%). The predictive value was not significantly different between flash goggle VEP(75%) and pattern reversal VEP(68%). The predictive value was higher in patient with visual field defect(100%) than those without visual field defect(25%). The pathologic nature of lesion also showed close relations to the predictive value. VEPs is usually paradoxically lateralized(78%), but not in all patients. Conclusion : VEPs abnormalities suggesting retrochiasmal lesion were usually corresponded with brain MRI findings. Diagnostic reliability could be increased when considering the visual field defect and nature of lesion. Therefore, the authors suggest that VEPs studies could be useful in evaluating the patients with the retrochismal lesion.

• Annals of Clinical Neurophysiology
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• v.20 no.1
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• pp.12-17
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• 2018

Visual evoked potentials (VEPs) are frequently used to assess the anterior and posterior visual pathways. In particular, the use of VEPs have been increasing in various fields such as evaluation of the optic nerves in patients with multiple sclerosis. The performance of VEP test can be affected by various factors such as stimulus type and subject condition, and its interpretation is also difficult. However, there have been no guidelines for performing and interpreting VEPs in Korea. Therefore, we aimed to provide comprehensive information regarding basic requirement and interpretation for VEPs.

• Journal of Biomedical Engineering Research
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• v.27 no.6
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• pp.384-391
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• 2006

Variation of brain dynamics under Zen meditation has been one of our major research interests for years. One issue encountered is the inaccessibility to the actual meditation level or stage as a reference. In this paper, we propose an alternative strategy for investigating the human brain in response to external flash stimuli during Zen meditation course. To secure a consistent condition of the brain dynamics when applying stimulation, we designed a recording of flash visual evoked potentials (F-VEPs) based on a constant background EEG (electroencephalograph) frontal $\alpha-rhythm$ dominating activities that increase significantly during Zen meditation. Thus the flash-light stimulus was to be applied upon emergence of the frontal $\alpha-rhythm$. The alpha-dependent F-VEPs were then employed to inspect the effect of Zen meditation on brain dynamics. Based on the experimental protocol proposed, considerable differences between experimental and control groups were obtained. Our results showed that amplitudes of P1-N2 and N2-P2 on Cz and Fz increased significantly during meditation, contrary to the F-VEPs of control group at rest. We thus suggest that Zen meditation results in acute response on primary visual cortex and the associated parts.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2002.05a
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• pp.44-50
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• 2002

The fast Fourier transform (FFT) is a good method to estimate spectral density, but the frequency resolution is limited to the sampling window, and thus the precise characteristics of the spectral density for short signals are not clear. To solve the limitation, a multiple band-pass filter was introduced to estimate the precise time course of the spectral density for flash visual evoked potentials (VEPs). Signals were recorded during -200 and 600 ms using balanced noncephalic electrodes, and sampled at 1 K Hz in 12 bits. With 1 Hz and 10 ms resolutions, spectral density was estimated between 10 and 100 Hz. Background powers at the alpha-and beta-bands were high over the posterior scalp, and powers around 200ms were evoked at the same bands over the same region, corresponding to P110 and N165 of VEPs. normalized's spectral density showed evoked powers around 200 ms and suppressed powers following the evoked powers over the posterior scalp. The evoked powers above the 20Hz band were not statistically significant. However, the gamma band was significantly evoked intra-individually; details in the gamma bands were varied among the subjects. Details of spectral density were complicated even for a simple task such as watching flashes; both synchronization and desynchronization occurred with different distributions and different time courses.

• Journal of Biomedical Engineering Research
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• v.26 no.2
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• pp.95-99
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• 2005

We have performed EEG current source imaging on the cortical surface using visual evoked potentials (VEPs) recorded inside a 3.0 T MRI magnet. In order to remove ballistocardiogram (BCG) artifacts in the VEPs, an improved BCG template subtraction technique is devised. Using the cortically constrained current source imaging technique and pattern-reversal visual stimulations, we have obtained current source maps from 10 subjects. To validate the EEG current source imaging inside the magnet, we have compared the current source maps to the ones obtained outside the magnet. The experimental results demonstrate that there is a strong correspondence between the current source maps, proving that current source imaging is feasible with the evoked potentials recorded inside a 3.0 T MRI magnet.

• Annals of Clinical Neurophysiology
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• v.22 no.2
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• pp.104-108
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• 2020

We performed intraoperative neurophysiological monitoring (INM) during anteromesial temporal resection (AMTR) in a patient with lesional temporal lobe epilepsy. INM revealed a sudden decrease in N20 waves in somatosensory evoked potentials (SSEPs) and poor P100 waves in visual evoked potentials (VEPs). These changes developed after applying electrocoagulation in the right mesial temporal areas. Postoperative brain magnetic resonance imaging demonstrated right thalamic and medial occipital infarctions. SSEPs and VEPs monitoring can be useful for detecting posterior cerebral artery infarction in AMTR.

• Korean Journal of Clinical Laboratory Science
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• v.45 no.2
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• pp.77-85
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• 2013

Intraoperative Neurophysiological Monitoring (INM) is very useful in monitoring the motorsensory pathway and vascular circulation system during intraspinal, or intracranial neurosurgery. Brainstem Auditory Evoked Potentials (BAEPs) are for detecting the problems along the auditory pathways including, the eighth cranial nerve and brainstem. Motor Evoked Potentials (MEPs) is a useful adjunct to conventional monitoring of Somato-sensory Evoked Potentials (SEPs) during surgery. Visual Evoked Potentials (VEPs) has been regarded as having limited significance for the preservation of visual function during neurosurgical procedures. In this paper, we propose that the most appropriate averaging of the number of inspections in the inspection of each used in the operative field, is good and efficient, functionally.

• The Journal of Korean Academy of Sensory Integration
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• v.8 no.1
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• pp.41-49
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• 2010

Objective : Multisensory integration (MSI) is the essential process to use diverse sensory information for cognitive task or execution of motor action. Especially, visual and somatosensory integration is critical for motor behavior and coordination. This study was designed to explain spatial and temporal characteristics of visual and somatosensory integration by neurophysiological research method that identifies the time course and brain location of the SI process. Methods : Electroencephalography (EEG) and event-related potential (ERP) is used in this study in order to observe neural activities when integrating visual and tactile input. We calculate the linear summation (SUM) of visual-related potentials (VEPs) and somatosensory-related potentials (SEPs), and compared the SUM with simultaneously presented visual-tactile ERPs(SIM) Results : There were significant differences between the SIM and SUM in later time epochs (about 200-300ms) at contralateral somatosensory areas (C4) and occipital cortices (O1&O2). The amplitude of the SIM was mathematically larger than the summed signals, implying that the integration made some extra neural activities. Conclusion : This study provides some empirical neural evidence of that multisensory integration is more powerful than just combing two unisensory inputs in the brain and ERP data reveals neural signature relating to multisensory integrative process. Since this study is preliminary pilot study, larger population and criteria are needed for level of the significance. Further study is recommended to consider issues including effect of internally-driven attention and laterality of interaction to make the evidence by this study solid.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.135-151
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• 2003

This study compared the effect of Polaroid$^{(R)}$ lenses on binocular vision by assessing visual acuity, stereopsis, and visual evoked potential(VEP), through Polaroid$^{(R)}$, CR 39 and sunglass lenses. The spectral absorptions of Polaroid$^{(R)}$, CR 39 and sunglass lenses were measured using a spectrophotometer (Hitachi. U-3501). The VEP were recorded by the Nicolet system. Thirty normal adult(fifteen males, fifteen females, mean=21.9 years, range=20 to 25) subjects were recorded. The subjects were provided a history including : general health, family health, medication, genetics, allergy and disease. All had normal or corrected to normal acuity with no history of visual disorders. Corrected visual acuity, colour vision and stereopsis were recorded for each subject monocularly and binocularly. Each test was repealed through the sunglass, CR 39, and Polaroid$^{(R)}$ lenses. Subjects viewed the VEP stimulus both monocularly and binocularly through the test lenses while the VEPs were recorded. The results suggest that the binocular visual acuity and stereoacuity is better than with monocular vision. On other hand, the analysis of VEP suggests that the amplitude of wave is smaller when the monocular eye receives the VEP stimulus compared with that when the binocular eye is stimulated by the VEP target with the sunglass, CR 39, and Polaroid$^{(R)}$ lens. But, the latency period of each eye was similar to results between the dominant eye and the non-dominant eye by the CR 39, sunglass, and polaroid lens. In conclusion, this study indicates that the binocular vision appears to be better through the brown Polaroid$^{(R)}$ lens than through the other test lenses.