• The Korean Journal of Physiology and Pharmacology
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• 제13권6호
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• pp.443-448
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• 2009

For successful visual perception by visual prosthesis using electrical stimulation, it is essential to develop an effective stimulation strategy based on understanding of retinal ganglion cell (RGC) responses to electrical stimulation. We studied RGC responses to repetitive electrical stimulation pulses to develop a stimulation strategy using stimulation pulse frequency modulation. Retinal patches of photoreceptor-degenerated retinas from rd1 mice were attached to a planar multi-electrode array (MEA) and RGC spike trains responding to electrical stimulation pulse trains with various pulse frequencies were observed. RGC responses were strongly dependent on inter-pulse interval when it was varied from 500 to 10 ms. Although the evoked spikes were suppressed with increasing pulse rate, the number of evoked spikes were >60% of the maximal responses when the inter-pulse intervals exceeded 100 ms. Based on this, we investigated the modulation of evoked RGC firing rates while increasing the pulse frequency from 1 to 10 pulses per second (or Hz) to deduce the optimal pulse frequency range for modulation of RGC response strength. RGC response strength monotonically and linearly increased within the stimulation frequency of 1~9 Hz. The results suggest that the evoked neural activities of RGCs in degenerated retina can be reliably controlled by pulse frequency modulation, and may be used as a stimulation strategy for visual neural prosthesis.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1628-1630
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• 1997

The purpose of this study is to see the method of the analysis of EEG(Electroencephalography) whcih is a nonlinear system, to quantize human emotion under color stimulation using the analysis of EEG. The result of this study would be used clinical study and development fo image instruments with color. In this study, the method of the analysis of EEG is power spectrum using FFT(Fast Fourier Transform) and the modelling of EEG under color stimulation base on back propagation Neural Networks ond of AI(Artfical Intellignece) skills. First, input layer make a match to relative power which get analyzing s in 4 channels, and output layer make a match to color stimulation which is measured human emotion. Finally, weights of each neurons determine by learing back porpagation Neural Networks.

• IEIE Transactions on Smart Processing and Computing
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• 제4권3호
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• pp.133-140
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• 2015

Neural stimulating implantable medical devices (IMDs) have been widely used to treat neurological diseases or interface with sensory feedback for amputees or patients suffering from severe paralysis. More recent IMDs, such as retinal implants or brain-computer interfaces, demand higher performance to enable sophisticated therapies, while consuming power at higher orders of magnitude to handle more functions on a larger scale at higher rates, which limits the ability to supply the IMDs with primary batteries. Inductive power transmission across the skin is a viable solution to power up an IMD, while it demands high power efficiencies at every power delivery stage for safe and effective stimulation without increasing the surrounding tissue's temperature. This paper reviews various wireless neural stimulating systems and their power management techniques to maximize IMD power efficiency. We also explore both wireless electrical and optical stimulation mechanisms and their power requirements in implantable neural interface applications.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.29-35
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• 2007

This study was designed to investigate the feasibility to utilize the electromyogram (EMG) for estimating the muscle torque. The muscle torque estimation plays an important role in functional electrical stimulation because electrical stimulation causes muscles to fatigue much faster than voluntary contraction, and the stimulation intensity should then be modified to keep the muscle torque within the desired range. We employed the neural network method which was trained using the major EMG parameters and the corresponding knee extensor torque measured and extracted during isometric contractions. The experimental results suggested that (1) our neural network algorithm and protocol was feasible to be adopted in a real-time feedback control of the stimulation intensity, (2) the training data needed to cover the entire range of the measured value, (3) different amplitudes and frequencies made little difference to the estimation quality, and (4) a single input to the neural network led to a better estimation rather than a combination of two or three. Since this study was done under a limited contraction condition, the results need more experiments under many different contraction conditions, such as during walking, for justification.

• 대한임상전기생리학회지
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• 제5권1호
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• pp.59-71
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• 2007

The purpose of this study was to study for the change of neural adaptation by muscle contraction force when neuromuscular electrical stimulation(NMES) was applied. Sixteen subjects(8 male, 8 female) without neuromuscular disease volunteered to participate in the study. All subjects were divided into two subgroups: control(no electrical stimulation) group, NMES(50% maximal voluntary isometric contraction) group. NMES training program was performed in the calf muscle over three times a week for 12 weeks. Before and after experiment MVIC of ankle plantar flexor was measured by use of dynamometer. H-reflex and V-wave in tibial nerve were measured. The following results were obtained; MVIC and V/Mmax ratio were significantly increased in the electrical stimulation groups. However, H/Mmax ratio was not changed. It was closely relationship between MVIC and V/Mmax ratio. In this study, the effect of neural adaptation of central neural adaptation was found in this study. Accordingly, NMES means not only a change of muscle fiber and skeletal muscle volume but also a effect of neural adaptation of central neural drive. Also, it was found that there was closely relationship between MVIC and neural adaptation of central neural drive by NMES.

• The Journal of Korean Physical Therapy
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• 제13권1호
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• pp.61-71
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• 2001

The purpose oi this study is to identify clearly the physiologic significance of autonomic nervous system. This study is to find the loose of endogenous neurotransmitter while using the neural response of the neural excitatory action which is distributed to the perivascular smooth muscle through the electrical stimulation of the smooth muscle of coronary artery of pig. The effects of perivascular nerve stimulation were investigated on isolated coronary artery of pig.1 . The magnitude of contractile response to perivascular nerve stimulation increased with increasing frequency (2-80 Hz) of stimulation. 2. The contractions to perivascular nerve stimulation(40V, 40Hz. 0.5msec, 1 min) were increased greatly by pretreatment of the cholinestrase inhibitor physostigmine. 3. The contraction to perivascular nerve stimulation(40V,40Hz, 0.5msec, 1min) was antagonised markedly by the muscarinic antagonist atropine. 4. The contraction to perivascular nerve stimulation(40V, 40Hz, 0.5msec, 1 min) was blocked by the neural blocker tetrodotoxin. 5. The contractions to perivascular nerve stimulation(40V. 40Hz, 0.5msec, 1 min) were not affected significantly by the -adrenergic antagonist phentolamine or - adrenergic antagonist propranolol. 6. The contractile response by the acetylcholine was increased by the pretreatment of cholinestrase inhibitor physostigmine. The finding suggest that it is powerful excitatory action linked to muscarinic receptor by cholinergic nerve in coronary artery of pig.

• 대한의용생체공학회:의공학회지
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• 제25권6호
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• pp.611-615
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• 2004

본 연구는 외부 전원 없이 광다이오드만을 이용하여 생성한 광전 자극을 통해 신경계를 효과적으로 자극하는 방법에 대한 것이다. 광을 통한 전류원 생성 및 전달은 생체 내에 집적된 광소자를 삽입하고 외부에서 광을 통해 신호와 전력을 전달을 한다. 이 기술은 특히 '눈' 이라는 광학적인 연결통로를 이용할 수 있는 인공망막과 같은 시스템에 매우 효과적이다. 그러나 광전 소자를 내부 전원 없이 구동시키는 경우, 광전류가 생체 저항에 직접적인 영향을 받게 되므로 자극에 충분한 전류를 생성할 수 없다. 무 전원 광다이오드를 통해 생성되는 광전류를 신경 자극에 적용하기 위해서는 생체 저항의 크기에 관계없이 활동 전위 생성에 충분한 전류 공급을 할 수 있는 안정된 전류원이 필요하다. 이를 위해서 본 연구에서는 병렬 저항을 도입하였다. 병렬 저항 추가 시 생체 저항을 포함한 전체 저항 값이 낮아지므로, 광원의 세기에 따라 최대의 광전류에 근접한 값을 얻을 수 있게 된다. 그러나 병렬 저항 값의 크기를 낮출수록 자극에 쓰이지 않는 전류량이 늘어나므로, 자극 전류량의 극대 값을 찾기 위해서는 병렬 저항 값의 최적화가 필요하다. 실험을 통해 측정된 실제 자극 전류량이 최대가 되는 병렬 저항 값의 범위는 500Ω∼700Ω 이고, 이때 전류량은 580uA∼860uA 이며 전류 효율은 47.5∼59.7%이었다. 자극의 크기와 빈1도를 변화시키면서 쥐의 좌골 신경을 자극하여 눈으로 확인 가능한 떨림 현상을 확인하였으며, 다채널 기록기를 이용해 활동 전위를 측정하였다. 이를 통해, 인공 망막에서의 광 자극 가능성을 확인할 수 있었다.

• 전자공학회논문지
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• 제52권5호
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• pp.58-65
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• 2015

본 논문에서는 신경 관련 인공 전자기기를 위한 신경 자극 집적회로를 $0.18-{\mu}m$ 표준 CMOS 반도체 공정을 이용하여 설계하였다. 제안 된 신경 자극 회로는 12.8-V 전원을 사용하면서 $10-k{\Omega}$의 부하에 최대 1 mA의 전류까지 전달이 가능하다. 표준 CMOS 공정 기술로 구현을 위해서 저전압 트랜지스터만을 이용하여 설계를 하였고, 고전압에서의 안정적인 동작을 위하여 트랜지스터 스태킹 기술을 적용하였다. 또한, 신경 자극 동작 후 전하 잔여량이 남아 있지 않도록 active charge balancing회로를 포함하였다. 제안 된 단일 채널 자극 집적회로의 경우 디지털-아날로그 변환기, 전류 출력 드라이버, 레벨 시프터, 디지털 제어 부분, 그리고 active charge balancing 회로까지 모두 포함하여 전체 칩 레이아웃 면적은 $0.13mm^2$을 차지하며, 다중 채널 방식의 신경 자극 기능의 체내 이식용 인공 전자기기 시스템에 적용을 하는데 적합하다.

• 센서학회지
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• 제20권1호
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• pp.19-24
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• 2011

Brain disorders such as epilepsy is a condition that affects an estimated 2.7 million Americans, 50,000,000 worldwide, approximately 200,000 new cases of epilepsy are diagnosed each year. Of the major chronic medical conditions, epilepsy is among the least understood. Scientists are conducting research to determine appropriate treatments, such as the use of drugs, vagus nerve stimulation, brain stimulation, and Peltier chip-based focal cooling. However, brain stimulation and Peltier chip-based stimulation processes cannot effectively stop seizures. This paper presents simulation of a novel heat enchanger network(HEN) technique designed to stop seizures by using a neural cooling probe to stop focal and spontaneous seizures by cooling the brain. The designed probe was composed of a U-shaped tube through which cold fluid flowed in order to reduce the temperature of the brain. The simulation results demonstrated that the neural probe could cool a 7 $mm^2$ area of the brain when the fluid was flowing atb a velocity of 0.55 m/s. It also showed that the neural cooling probe required 23 % less energy to produce cooling when compared to the Peltier chip-based cooling system.

• The Korean Journal of Physiology and Pharmacology
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• 제13권3호
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• pp.221-227
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• 2009

For successful restoration of visual function by a visual neural prosthesis such as retinal implant, electrical stimulation should evoke neural responses so that the informat.ion on visual input is properly represented. A stimulation strategy, which means a method for generating stimulation waveforms based on visual input, should be developed for this purpose. We proposed to use the decoding of visual input from retinal ganglion cell (RGC) responses for the evaluation of stimulus encoding strategy. This is based on the assumption that reliable encoding of visual information in RGC responses is required to enable successful visual perception. The main purpose of this study was to determine the influence of inter-dependence among stimulated RGCs activities on decoding accuracy. Light intensity variations were decoded from multiunit RGC spike trains using an optimal linear filter. More accurate decoding was possible when different types of RGCs were used together as input. Decoding accuracy was enhanced with independently firing RGCs compared to synchronously firing RGCs. This implies that stimulation of independently-firing RGCs and RGCs of different types may be beneficial for visual function restoration by retinal prosthesis.