• Science of Emotion and Sensibility
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• v.22 no.3
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• pp.3-20
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• 2019

With advancements in technology of virtual reality, it is used for various purposes in many fields such as medical care and healthcare, but as the same time there are also increasing reports of nausea, eye fatigue, dizziness, and headache from users. These symptoms of motion sickness are referred to as cybersickness, and various researches are under way to solve the cybersickness problem because it can cause inconvenience to the user and cause adverse effects such as discomfort or stress. However, there is no official standard for the causes and solutions of cybersickness at present. This is also related to the absence of tools to quantitatively measure the cybersickness. In order to overcome these limitations, this study proposed quantitative and objective cybersickness evaluation method. We measured 128-channel EEG waves from ten participants experiencing visually stimulated virtual reality. We calculated the relative power of delta and alpha in 11 regions (left, middle, right frontal, parietal, occipital and left, right temporal lobe). Multiple regression models were obtained in a stepwise manner with the motion sickness susceptibility questionnaire (MSSQ) scores indicating the susceptibility of the subject to the motion sickness. A multiple regression model with the highest under the area ROC curve (AUC) was derived. In the multiple regression model derived from this study, it was possible to distinguish cybersickness by accuracy of 95.1% with 11 explanatory variables (P_D.MF, P_D.LP, P_D.MP, P_D.RP, P_D.MO, P_A.LF, P_A.MF, P_A.RF, P_A.LP, P_A.RP, P_A.MO). In summary, in this study, objective response to cybersickness was confirmed through 128 channels of EEG. The analysis results showed that there was a clearly distinguished reaction at a specific part of the brain. Using the results and analytical methods of this study, it is expected that it will be useful for the future studies related to the cybersickness.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.11 no.2
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• pp.128-140
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• 2007

Purpose: We performed this study to examine the correlationship between EEG complexity and impedance cardiography data using correlation analysis. Method: This study performed on 30 healthy subjects(16 males, 14 females). Before and after natural respiration, ICG data were recorded, and EEG raw data were measured by moving windows during 15 minutes. The correlation dimension(D2) was calculated from 15 minutes data. 8 channels EEG data were analysed with 9 index of ICG data by correlation analysis. Result: 1. ACI of impedance cardiography had significant correlationship with ch.4 of EEG complexity(p=0.03). 2. VI of impedance cardiography had significant correlationship with ch.3 of EEG complexity(p=0.034) and ch.4 of EEG complexity(p=0.017). 3. HR, TFC, PEP, LVET, STR of impedance cardiography had no significant correlationship with all of 8 channel EEG complexity. Conclusions: These results suggest that nonlinear analysis of EEG and impedance cardiography have some significant correlationship. And it can make out relationship between brain system and cardiovascular system. In the future, therefore, more study of these fields are necessary.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2005.05a
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• pp.151-153
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• 2005

We investigated the brain substrate of repetition priming on the implicit memory taskusing low-resolution electromagnetic tomography (LORETA) with high-density 128 channel EEG and individual MRI as a realistic head model. Thirteen right-handed, healthy subjects performed a word/nonword discrimination task, in which the words and nonwords were presented visually,and some of the words appeared twice with a lag of one or five items. All of the subjects exhibited repetition priming with respect to the behavioral data, in which a faster reaction time was observed to the repeated word (old word) than to the first presentation of the word (new word). The old words elicited more positive-going potentials than the new words, beginning at 200 ms and lasting until 500 ms post-stimulus. We conducted source reconstruction using LORETA at a latency of 400 ms with the peak mean global field potentials and used statistical parametric mapping for the statistical analysis. We found that the source elicited by the old words exhibited a statistically significant current density reduction in the left inferior frontal gyrus. This is the first study to investigate the generators of repetition priming using voxel-by-voxel statistical mapping of the current density with individual MRI and high-density EEG.

• Anxiety and mood
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• v.6 no.1
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• pp.31-36
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• 2010

Objective : Mismatch negativity (MMN) provides an electrophysiological index of an involuntary attention switching process. This study investigated MMN anomalies and their relationship to clinical variables in patients with obsessive-compulsive disorder (OCD). Methods : Study participants were 29 OCD patients and 24 normal controls. We used a 128-channel EEG to measure MMN during a passive oddball paradigm. Then we assessed the correlations between MMN amplitudes and clinical measures. Results : The OCD patients exhibited significantly greater MMN amplitude compared to the controls. Also, the right frontal lobe MMN amplitudes correlated significantly to the OCD patients' Yale-Brown Obsessive Compulsive Scale total scores (r=-0.520, p=0.005). Conclusion : These results suggest that MMN anomalies in OCD patients reflect a monitoring circuit dysfunction, raising the possibility that the OCD's pathophysiology includes glutamatergic dysfunction.

• Korean Journal of Biological Psychiatry
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• v.10 no.2
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• pp.168-176
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• 2003

Objectives:We investigated the characteristics of P300 generators in obsessive-compulsive disorder(OCD) patients by using voxel-based statistical parametric mapping of current density images. Methods:P300 generators, produced by a rare target tone of 1500Hz under a frequent non-target tone of 1,000Hz, were measured in 15 right-handed OCD patients and 15 controls. Low Resolution Electromagnetic Tomography(LORETA), using a realistic head model of the boundary element method based on individual MRI, was applied to the 128-channel EEG. Statistical parametric mapping(SPM) was applied for the statistical analysis. Results:We found that both groups had the mean current density of P300 in the parietal, temporal and prefrontal lobe. There was a trend for decreased current density in the prefrontal area in OCD patients. The statistical comparison showed current density increase in the supraparietal area, a statistically significant longer P300 latency and a trend for reduced P300 amplitude in OCD patients. Conclusion:It suggests that P300 source of both groups exists in multiple brain regions at the same time. And both groups had no statistically significant differences in the current density of P300 except for increased current density in the supraparietal area in OCD patients. But, considering the statistically significant longer P300 latency, a trend for reduced P300 amplitude and relative mean current density reduction in the prefrontal area in OCD patients, this study suggests that the frontal lobe may have a reduced normal inhibitory process in OCD patients.

• Korean Journal of Biological Psychiatry
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• v.8 no.2
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• pp.251-257
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• 2001

Backgrounds : Gamma band oscillatory activity is considered to be related to cognitive functions and illustrates that the concept of event-related oscillations bridges the gap between single neurons and neural assemblies. An event-related gamma oscillation is the time-locked responses of specific frequency, and can be identified by computing the amplitude frequency characteristics of the averaged event-related potentials(ERPs) after stimulation. Objectives : We purposed to present experimental paradigm to investigate ${\gamma}$-band oscillation activities from the recording of ERPs by using auditory oddball paradigm and investigate the difference of ${\gamma}$-band activity between schizophrenia and normal controls. Methods : The ERPs resulting from auditory stimuli with oddball paradigm in a group of schizophrenics(n=11), and also a group of age-, sex-, and handedness matched normal controls, were recorded by 128 channel EEG. The ${\gamma}$-band oscillatory activities were calculated by using time-frequency wavelet decomposition of the signal between 20 and 80Hz. The ${\gamma}$-band oscillatory activities of both groups were compared by t-test. Results : The ${\gamma}$-band oscillatory of the leads Fz, Cz, and Pz of both groups were represented well in the time-frequency maps. Significant increases of the ${\gamma}$-band activity in normal controls compared with schizophrenics were observed around 160 msec, 350 msec, and 800 msec after stimulation. Conclusions : Our results suggested that the increment in ${\gamma}$-band oscillatory activity during cognitive operations and decreased ${\gamma}$-band activity in schizophrenics may be associated with the cognitive dysfunctions and the pathophysiology of the schizophrenia.