ECG), Electroencephalography Research Articles

부정감성 인식을 위한 생체신호 기반의 특징 선택 알고리즘 개발

감성은 인간의 삶과 밀접한 관련을 가지고 있으며 이는 집중력, 학습능력 등 많은 부분에 영향을 주어 다양한 행동 패턴을 가지게 한다. 따라서 본 논문의 목적은 부정감성을 구분하기 위하여 생체신호를 기반으로 주요한 특징들을 추출하는 것이다. 이를 위해 본 논문에서는 심전도, 뇌파, 피부 온도와 피부전도도를 기반으로 생체신호를 측정한 후, 선형분류기와 유전 알고리즘의 조합으로 정확하고 신속한 알고리즘 개발하고, 주요 특징을 추출하였다. 그 결과, 알고리즘은 최대 96.4%의 정확도를 가짐을 확인할 수 있었고, 추출된 파라미터는 심박변이도의 Mean, RMSSD, NN50과 뇌파의 전두엽 영역에서의 <TEX>${\sigma}$</TEX>파와 <TEX>${\alpha}$</TEX>파의 주파수 파워, 두정엽 영역에서 <TEX>${\alpha}$</TEX>파, <TEX>${\beta}$</TEX>파, <TEX>${\gamma}$</TEX>파와 의 주파수 파워, 그리고 피부온도의 평균과 표준편차 값이었다. 이에 따라 각 각의 생체신호를 기반으로 한 추출 된 특징들은 부정감성의 분류에 있어 중요한 역할을 함을 확인할 수 있었다. Emotion is closely related to the life of human, so has effect on many parts such as concentration, learning ability, etc. and makes to have different behavior patterns. The purpose of this paper is to extract important features based on physiological signals to recognize negative emotion. In this paper, after acquisition of electrocardiography(ECG), electroencephalography(EEG), skin temperature(SKT) and galvanic skin response(GSR) measurements based on physiological signals, we designed an accurate and fast algorithm using combination of linear discriminant analysis(LDA) and genetic algorithm(GA), then we selected important features. As a result, the accuracy of the algorithm is up to 96.4% and selected features are Mean, root mean square successive difference(RMSSD), NN intervals differing more than 50ms(NN50) of heart rate variability(HRV), <TEX>${\sigma}$</TEX> and <TEX>${\alpha}$</TEX> frequency power of EEG from frontal region, <TEX>${\alpha}$</TEX>, <TEX>${\beta}$</TEX>, and <TEX>${\gamma}$</TEX> frequency power of EEG from central region, and mean and standard deviation of SKT. Therefore, the features play an important role to recognize negative emotion.

Conductive polymer combined silk fiber bundle for bioelectrical signal recording.

Electrode materials for recording biomedical signals, such as electrocardiography (ECG), electroencephalography (EEG) and evoked potentials data, are expected to be soft, hydrophilic and electroconductive to minimize the stress imposed on living tissue, especially during long-term monitoring. We have developed and characterized string-shaped electrodes made from conductive polymer with silk fiber bundles (thread), which offer a new biocompatible stress free interface with living tissue in both wet and dry conditions.An electroconductive polyelectrolyte, poly(3,4-ethylenedioxythiophene) -poly(styrenesulfonate) (PEDOT-PSS) was electrochemically combined with silk thread made from natural Bombyx mori. The polymer composite 280 µm thread exhibited a conductivity of 0.00117 S/cm (which corresponds to a DC resistance of 2.62 Mohm/cm). The addition of glycerol to the PEDOT-PSS silk thread improved the conductivity to 0.102 S/cm (20.6 kohm/cm). The wettability of PEDOT-PSS was controlled with glycerol, which improved its durability in water and washing cycles. The glycerol treated PEDOT-PSS silk thread showed a tensile strength of 1000 cN in both wet and dry states. Without using any electrolytes, pastes or solutions, the thread directly collects electrical signals from living tissue and transmits them through metal cables. ECG, EEG, and sensory evoked potential (SEP) signals were recorded from experimental animals by using this thread placed on the skin. PEDOT-PSS silk glycerol composite thread offers a new class of biocompatible electrodes in the field of biomedical and health promotion that does not induce stress in the subjects.

A NOVEL NARROW BANDPASS FILTER FOR IMAGE REJECTION AND CHANNEL SELECTION IN A WIRELESS SLEEP APNOEA MONITORING SYSTEM

A highly compact bandpass fllter (BPF) is designed with a capacitively-coupled compact ring resonator. The ground plane is perturbed with a combination of two inter-digital and two spiral defected ground structures (DGSs), which enhance the selectivity and suppress the higher order harmonics of the BPF respectively. The fllter has a selectivity of 0.22dB/MHz, passband insertion loss (IL) of 1.55dB and bandwidth of 61MHz at 2.53GHz. The proposed compact ring resonator yields a size reduction of 70.5% compared to a conventional ring resonator. This BPF is signiflcant for wireless telemetry monitoring systems for physiological parameters including electrocardiogram (ECG), electroencephalography (EEG) and electromyography (EMG) using portable devices.

COMPUTING MULTISCALE ENTROPY WITH ORTHOGONAL RANGE SEARCH

Multi-scale entropy (MSE) is a measurement of a system's complexity. It has received a great deal of attention in recent years, and its effectiveness has been verified, and applied in a number of different fields. However, the algorithms proposed in past studies required O (N^2), which represented a degree of execution time insufficient for on-line applications, or for applications with long term correlations. In this study, we showed that the probability function in the entropy term could be transformed into an orthogonal range search in the field of computational geometry. We then developed an efficient new algorithm for computing multi-scale entropy. The execution time in the results of our experiments with electrocardiogram (ECG), electroencephalography (EEG), interbeat interval (RR), and mechanical and ecological signals showed a significant improvement from 10 to 70 times over that of conventional methods for N=80, 000. Because the execution time has been significant reduced, the new algorithm could be applied to online diagnosis, in the computation of MSE for long-term correlation of signal.

Vagus nerve stimulation induces changes in respiratory sinus arrhythmia of epileptic children during sleep

This study analyzed the direct short-term effect of vagus nerve stimulation (VNS) on respiratory sinus arrhythmia (RSA) in children with pharmacoresistant epilepsy. RSA magnitude is calculated as the ratio between maximum and minimum heart rate for each respiratory cycle-before, during, and after the actual VNS period. In 10 children, changes in RSA magnitude were evaluated on polysomnographic recordings, including electrocardiography (ECG), electroencephalography (EEG), thoracoabdominal distension, nasal airflow, and VNS artifacts. Measurements during stimulation were compared with those at baseline, immediately preceding the VNS periods and individually for each patient. During VNS, respiratory frequency increased and respiratory amplitude decreased with a variable effect on cardiac activity. The coupling between heart rate and respiratory rate was disturbed and RSA magnitude decreased significantly in 6 of 10 children during VNS. These changes in RSA magnitude varied from one child to another. The observed changes for respiratory and cardiac activity were concomitant with changes in RSA but were not correlated. Together with disorders of respiration, cardiac activity, and oxygen saturation (SaO(2)) described previously. VNS also modifies synchronization between cardiac and respiratory activity, resulting in poor optimization of oxygen delivery to tissues that can be regarded as an additive side effect, which should be considered in patients with already altered brain function. This interaction between the effects of VNS and potential autonomic nervous system (ANS) dysfunction already reported in epileptic patients should be considered to be potentially life-threatening. In addition, evaluation of changes in respiratory parameters can also provide reliable markers for further evaluation of the effectiveness of VNS.

Imaging seizure activity: A combined EEG/EMG‐fMRI study in reading epilepsy

To characterize the spatial relationship between activations related to language-induced seizure activity, language processing, and motor control in patients with reading epilepsy. We recorded and simultaneously monitored several physiological parameters [voice-recording, electromyography (EMG), electrocardiography (ECG), electroencephalography (EEG)] during blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in nine patients with reading epilepsy. Individually tailored language paradigms were used to induce and record habitual seizures inside the MRI scanner. Voxel-based morphometry (VBM) was used for structural brain analysis. Reading-induced seizures occurred in six out of nine patients. One patient experienced abundant orofacial reflex myocloni during silent reading in association with bilateral frontal or generalized epileptiform discharges. In a further five patients, symptoms were only elicited while reading aloud with self-indicated events. Consistent activation patterns in response to reading-induced myoclonic seizures were observed within left motor and premotor areas in five of these six patients, in the left striatum (n = 4), in mesiotemporal/limbic areas (n = 4), in Brodmann area 47 (n = 3), and thalamus (n = 2). These BOLD activations were overlapping or adjacent to areas physiologically activated during language and facial motor tasks. No subtle structural abnormalities common to all patients were identified using VBM, but one patient had a left temporal ischemic lesion. Based on the findings, we hypothesize that reflex seizures occur in reading epilepsy when a critical mass of neurons are activated through a provoking stimulus within corticoreticular and corticocortical circuitry subserving normal functions.

The characteristics of neurocardiogenic syncope in children

Purpose : Syncope is relatively common in children and adolescents. Among the etiologies of syncope, neurocardiogenical syncope is the most common, but it is often confounded with seizure. We investigated the clinical features of patients under the age of 15 with neurocardiogenical syncope, compared to patients with neurologic disorders including epilepsy. Methods : Among the children who visited the Department of Pediatrics at Cheongju St. Mary's Hospital and Chungbuk National University Hospital from March 2005 to February 2007, we retrospectively analyzed 69 patients whose chief complaint was syncope. We classified the patients by syncope etiology and made comparisons between the neurocardiogenical syncope (NCS) group and the neurological disorders (ND) group regarding to age; location; time and season in which syncope occurred; associated symptoms, including seizures, provocation factors; prodromes; duration of syncope; frequency of previous syncope; birth history; associated disease; past medical history; family history; neurological exam; physical exam; laboratory findings; electrocardiography; electroencephalography (EEG); head-up tilt test; brain CT; and MRI. Results : Among 69 syncope patients, 53 (76.8%) were in the NCS group and 11 (15.9%) were in the ND group. There were no statistically significant differences between the two study groups except for the presence of prodromes and EEG abnormalities. The presence of prodromes in the NCS group was more common than in the ND group [46.9% (23/49) vs. 9.1% (1/11), (P=0.038)]. The EEG abnormality in the ND group was more common than in the NCS group [90% (9/10) vs. 5.8% (3/52), (P

Dysrhythmia as a cause of syncope in children without neurological or cardiac morphological abnormalities.

Arrhythmias are among the malignant causes of syncope. This study has been undertaken to determine the relative incidence and significance of dysrhythmia in the pathogenesis of syncope among patients referred to a pediatric cardiology unit. Between March 1997 and March 1999, 105 consecutive patients (59 female, 46 male) aged 11.5 +/- 3.6 years without neurologic or cardiac morphologic causes were evaluated for at least one episode of syncope. A pediatric cardiologist and a pediatric neurologist evaluated all the patients. Routine chest X-ray, 12-lead electrocardiogram (ECG), electroencephalography (EEG), 24-h Holter monitoring and echocardiography were carried out. When deemed necessary, further tests were undertaken for the cases of syncope which were unexplained by routine tests. The cause of syncope was identified as vasovagal in 25.7% (n = 27) and related to dysrhythmia in 30.5% (n = 32). The cause was migraine-associated syncope in two children, psychogenic syncope in three children and orthostatic hypotension in one patient. The cause was unknown in 36.2% (n = 38). We conclude that dysrhythmia is a significant and frequent cause in children referred to pediatric cardiology units. The combination of ECG, Holter monitoring, electrophysiologic study, transtelephonic ECG and head-up tilt test can identify the underlying cause of syncope in as many as 58% of these patients that present with syncope.