• Journal of Biomedical Engineering Research
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• v.17 no.2
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• pp.179-188
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• 1996

A clinically oriented 32-channel electroencephalogram (EEG) and evoked potential (EP) mapping system has been developed EEG and EP signals acquired from 32-channel electrodes attached on the heroid surface are amplified by a pre-amplifier which is separated from main amplifier and is located near the patient to reduce signal attenuation and noise contamination between electrodes and the amplifier. The amplified signals are further amplified by a main amplifier where various filtering and gain contr61 are achieved An automatic artifact rejection scheme is employed using neural network-based EEG and artifact classifier, by which examination time is substantially reduce4 The continuously measured EEG sigrlals are used for spectral mapping, and auditory and visual evoked potentials measured in synchronous to the auditory and visual stimuli are used for temporal 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 comparisons of group and individual are included to support a statistically-based diagnosis.

• Annals of Clinical Neurophysiology
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• v.1 no.2
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• pp.160-167
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• 1999

Although somatosensory evoked potentials(SSEPs) have been utilized as the useful diagnostic tools in evaluating the wide variety of pathological conditions, such as focal lesions affecting the somatosensory pathways, demyelinating diseases, and detecting the clinically occult abnormality, their neural generators is still considerably uncertain. To appreciate the basis for uncertainties about the origins of SSEPs, consider criteria that must be met to establish a causal relationship between activity in a neural structure and a spine/ scalp-recorded potential. Electrode locations and channel derivations for SSEPs recordings are based on two principles:(1) the waveforms are best recorded from electrode sites on the body surface closest to the presumed generator sources along the somatosensory pathways, and(2) studies of the potential-field distribution of each waveform of interest dictate the best techniques to be used. In this article, authors will describe followings focused on ;(1) the concepts of near field potentials(NFPs) and far field potentials(FFPs) - the voltage of NFPs is highly dependent upon recording electrode position, FFPs are unlike NFPs in that they are widely distributed, their latencies and amplitudes are independent of recording electrode.(2) appropriate montage settings to detect the significant potentials in the median nerve and posterior tibial nerve SSEPs(3) neural generators of various potentials(P9, N13, P14, N18, N20, P37) and their clinical significance in interpretating the results of SSEPs. Especially, Characteristics of N18(longduration, small superimposed inflection) suggested that N18 is a complex wave with multiple generators including brainstem structures and thalamic nuclei. And N18 might be used as the parameter of braindeath. Precise understanding on these facts provide an adequate basis utilizing SSEPs for numerous clinical purposes.

• Annals of Clinical Neurophysiology
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• v.1 no.2
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• pp.99-105
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• 1999

Background and Objectives : The Motor evoked potentials (MEP) study may be useful in the evaluation of the degree of impairment in the motor nervous system and in the determination of the prognosis. The purpose of this study is to evaluate the status of central nervous system in acute and subacute state of cerebral ischemia by comparing the changes of MEP in the initial and follow-up study. Methods : Twenty patients with hemiparesis caused by ischemic stroke were recruited for this study. We tested MEP within 7 days and followed-up after 14 days after symptom onset. The cerebral motor cortex area, cervical area for upper extremity and lumbar area for lower extremity were stimulated by transmagnetic stimulator. The central motor conduction time(CMCT) was measured with the difference in MEP caused by stimulating the vertical area and spinal area. The CMCT of hemiparetic patients were classified into three groups-normal, delayed, and no evoked MEP groups. Results : The CMCT in hemiparetic side of acute ischemic stroke patients were singnificantly delayed (P < 0.05) compared with the control group. The CMCT of hemiparetic side in the follow-up study showed no sinificantly difference in comparison to the control group. The prognosis of motor improvement was better in the groups of delayed MEP than the groups of no evoked MEP. Conclusion : The CMCT of hemiparetic and contralateral sides were delayed in acute ischemic stroke, compared with control group and were returned to normal boundaries in subacute state. But in the most cases with no MEP response in the initial study, also showed no MEP response in the follow-up study. The recovery occurred in the subacute state in cases with mild hemiparesis, whereas recovery did not occur in the subacute stage in case with severe hemiparesis.

• Annals of Clinical Neurophysiology
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• v.2 no.2
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• pp.107-113
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• 2000

Background & Objectives : Motor evoked potentials(MEPs) to magnetic trans cranial stimulation were performed to evaluate upper motor neuron involvement and relationship to lower motor neuron involvement in motor neuron disease patients. Method : MEPs were obtained in the 17 consecutive patients with motor neuron disease. These patients were divided into three group based on clinical evidence of upper and lower motor neuron involvement, bulbar symptom; amyotrophic lateral sclerosis(ALS), progressive muscular atrophy(PMA), progressive bulbar palsy(PBP). MEPs were recorded from abductor pollicis brevis and abductor hallucis muscles. Abnormal MEPs were defined by delayed central motor conduction time or absent MEP. Results : MEPs were abnormal in 64%(11/17) of patients; 100%(7/7) in ALS, 64%(4/7) in PMA, 0%(0/3) in PBP respectively. In 68 total recording muscles, 34 muscles had evidence of motor weakness and showed abnormal responses in 59%(20/34). Whereas 34 muscles with normal strength, only 3%(1/34) of muscles showed abnormal response. Conclusion : MEPs are well correlated with upper motor neuron signs in ALS and may detect masking upper motor neuron signs in PMA. The muscles with lower motor neuron sign(weakness) usually relate with abnormal MEPs reponses.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.2
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• pp.198-204
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• 2019

Various treatments can be attempted in patients with intractable epilepsy, in whom the symptoms of seizures are not controlled by various drugs. On the other hand, in patients requiring a surgical method, a preoperative examination is needed to determine the portion of seizure site to be resected. Electrodes are inserted into the cerebral cortex for accurate lesion measurements and safe operation. The electrodes inserted in the cortex not only record the electroencephalography (EEG), but also allow various tests to confirm the function of the part. One of these methods is the evoked potential test. From January 2015 to December 2018, the trends of measured waveforms in were analyzed 70 patients. The somatosensory evoked potential (SSEP) recorded on the electrode inserted in the cerebral cortex can be searched for the pathway of the central sulcus to avoid the primary motor area and primary sensory area. In addition, using the middle latency auditory evoked potentials (MLAEP) and flash visual evoked potentials (FVEP), the functional cortex in the auditory cortex and the visual cortex were compared with the seizure focus point on the EEG to help determine the location of the ablation and minimize functional impairment after surgery.

• Journal of Biomedical Engineering Research
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• v.13 no.1
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• pp.39-46
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• 1992

This paper proposes the method that evoked potentials stimulated by object colors are analyzed and examined on the phenomemon of color sensory. The method which is used to estimate the signal is time-varying. filtering (TVF). At the results of experiment which used object colors, it is shown that color sensory times of red are within the range of 0.0~0.25[sec], those of yellow are within the range of 0.25~0.55[sec], and those of blue are within the range of 0.55~0.75[sec]; they are inclined to sequence in accending order as red, yellow, and blue.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.247-250
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• 1996

In this paper, we tried to analyze the mental states, especially alertness or degree of concentration, by analysis of Visual Evoked Potentials. Given task to the visual stimulation, there was warning signals to enhance the alertness of the subject. With the synchronization to the stimulus, we averaged the EP waves, and estimated the power spectrums to view difference between relatively less alerted state and more alerted state. Although there was no significant difference during the waiting for the stimuli, we could find some difference during task performing.

• Journal of Biomedical Engineering Research
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• v.22 no.2
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• pp.187-195
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• 2001

시각자극 유발전위 추론시에 사용되는 평균법은 많은 회수의 단일-시도 유발전위(single-trial evoked potential)의 기록이 필요하다. 본 논문에서는 이러한 평균법의 후처리기로서 Prony 방법을 적용하여 향상된 신호-대-잡음비를 제공하는 방법을 제안하였다. Prony 방법은 유발전위와 같은 잡음이 섞여 있는 신호에서 지수함수를 추론하는데 많이 적용되어져 왔다. 여러 가지 잡음 모델을 이용한 시뮬레이션과 실제 시각자극 유발전위 데이터를 이용한 실험을 통해 Prony 방법이 평균법의 후처리기(post-processor) 기능으로서 사용될 때, 신호의 질적인 향상 측면 뿐 아니라 평균법 사용시 단일-시도 유발전위의 기록 횟수의 단축이라는 결과도 가져옴을 보였다.

• Journal of Biomedical Engineering Research
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• v.15 no.2
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• pp.135-142
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• 1994

This paper presents average method to detect Visual-Transient Evoked Potential from the human scalp electric potential measured by the ElectroEncephaloGram. To confirm the validity of average method, the average-process is performed with both stimulated and no-stimulated potentials respectively, and both results are compared. The specific waveform, which is visual-transient evoked potential, is produced only in the case of stimulated potential. It was found that a dc-drift, due to instrumentation errors and other noises, can produce significant changes in the evoked-potential waveform. This can be removed with a high-pass filter (cut-off frequency=0.5Hz).

• Journal of Biomedical Engineering Research
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• v.22 no.3
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• pp.241-247
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• 2001

ABR(auditory brainstem response) is one of the audiometry which measures objective hearing threshold level by acquiring electric evoked potentials emanated from auditory nerve system responding to an auditory stimulation. However, the obtained potentials which are largely interfered by power line noise, have extremely low SNR, thus ensemble average algorithm is generally used. The purpose of this study was to investigate the effect of iteration number in ensemble average on the reduction of the power line noise. The power line noise was modeled to be a 60 Hz sinusoidal signal and the energy of the modeled signal was calculated when it was averaged. It was verified by simulation that the energy had the periodic zero points for each stimulation rate, and 60 Hz signal induced by the power line was applied to the developed ABR system to confirm that the period of zero energy point was the same with that of the simulation. By the properly selected iteration number, power line noise could be reduced and more reliable ABR could be acquired.