Recovery time from VR sickness due to susceptibility: Objective and quantitative evaluation using electroencephalography.

With the increasing use of virtual reality (VR) devices, interest in reducing their negative effects, such as VR sickness, is also increasing. This study used electroencephalography (EEG) to investigate participants' VR sickness recovery time after watching a VR video. We tested 40 participants in advance using a motion sickness susceptibility questionnaire (MSSQ). We classified the participants into two groups (sensitive group/non-sensitive group) depending on their MSSQ scores. We used a simulator sickness questionnaire (SSQ) and EEG to evaluate VR sickness. The SSQ score increased significantly after watching the VR sickness-inducing video (VR video) in both groups (p < 0.001). The recovery time based on the SSQ was 11.3 ± 6.6 min for the sensitive group and 9.1 ± 5.2 min for the non-sensitive group. The difference in recovery time between the two groups was not significant (p > 0.05). EEG results showed that recovery time took an average of 11.5 ± 7.1 min in both groups. The EEG data showed that the delta wave increased significantly across all brain areas (p < 0.01). There was no statistical difference between groups in recovering VR sickness depending on individual characteristics. However, we confirmed that subjective and objective VR recovery required at least 11.5 min. This finding can inform recommendations regarding the VR sickness recovery times.

Motor Development Comparison between Preterm and Full-Term Infants Using Alberta Infant Motor Scale.

The Alberta Infant Motor Scale (AIMS) was developed to evaluate the motor development of infants up to 18 months of age. We studied 252 infants in three groups (105 healthy preterm infants (HPI), 50 preterm infants with brain injury (PIBI), and 97 healthy full-term infants (HFI) under 18 months, corrected age (CoA)) using AIMS. No significant differences were found among HPI, PIBI, and HFI in infants less than 3 months old, yet significant differences were noted in positional scores (p < 0.05) and total scores for those four to six months of age and seven to nine months of age. A significant difference was also found in standing items for infants over 10 months (p < 0.05). After four months, there was a difference in motor development between preterm (with and without brain injury) and full-term infants. In particular, there was a significant difference in motor development between HPI and HFI and between PIBI and HFI at four to nine months, when motor skills developed explosively (p < 0.05). After four months, motor developmental delays (10th ≥) were observed in HPI and PIBI at rates of 26% and 45.8%, respectively. Midline supine development, a representative indicator of early motor development, was slower even in healthy preterm infants than in full-term infants. AIMS has a good resolution to discriminate preterm infants who are showing insufficient motor development from 4 months to 9 months.

Electroencephalogram microstates and functional connectivity of cybersickness.

Virtual reality (VR) is a rapidly developing technology that simulates the real world. However, for some cybersickness-susceptible people, VR still has an unanswered problem-cybersickness-which becomes the main obstacle for users and content makers. Sensory conflict theory is a widely accepted theory for cybersickness. It proposes that conflict between afferent signals and internal models can cause cybersickness. This study analyzes the brain states that determine cybersickness occurrence and related uncomfortable feelings. Furthermore, we use the electroencephalogram (EEG) microstates and functional connectivity approach based on the sensory conflict theory. The microstate approach is a time-space analysis method that allows signals to be divided into several temporarily stable states, simultaneously allowing for the exploration of short- and long-range signals. These temporal dynamics can show the disturbances in mental processes associated with neurological and psychiatric conditions of cybersickness. Furthermore, the functional connectivity approach gives us in-depth insight and relationships between the sources related to cybersickness. We recruited 40 males (24.1 ± 2.3 years), and they watched a VR video on a curved computer monitor for 10 min to experience cybersickness. We recorded the 5-min resting state EEG (baseline condition) and 10-min EEG while watching the VR video (task condition). Then, we performed a microstate analysis, focusing on two temporal parameters: mean duration and global explained variance (GEV). Finally, we obtained the functional connectivity data using eLoreta and lagged phase synchronization (LPS). We discovered five sets of microstates (A-E), including four widely reported canonical microstates (A-D), during baseline and task conditions. The average duration increased in microstates A and B, which is related to the visual and auditory networks. The GEV and duration decreased in microstate C, whereas those in microstate D increased. Microstate C is related to the default mode network (DMN) and D to the attention network. The temporal dynamics of the microstate parameters are from cybersickness disturbing the sensory, DMN, and attention networks. In the functional connectivity part, the LPS between the left and right parietal operculum (OP) significantly decreased (p < 0.05) compared with the baseline condition. Furthermore, the connectivity between the right OP and V5 significantly decreased (p < 0.05). These results also support the disturbance of the sensory network because a conflict between the visual (V5) and vestibular system (OP) causes cybersickness. Changes in the microstates and functional connectivity support the sensory conflict theory. These results may provide additional information in understanding brain dynamics during cybersickness.

Estimating objective (EEG) and subjective (SSQ) cybersickness in people with susceptibility to motion sickness.

Cybersickness refers to the uncomfortable side effects, such as headaches, dizziness, and nausea, felt while experiencing virtual reality (VR). This study investigated cybersickness in people with sensitivity to motion sickness using electroencephalography (EEG), the Simulator Sickness Questionnaire (SSQ), and simple VR content. Based on the scores from the Motion Sickness Susceptibility Questionnaire (MSSQ), 40 males in their twenties were selected as the sensitive group (n = 20) and non-sensitive group (n = 20). The experiment contained two conditions: a baseline condition representing a resting state and a cybersickness condition in which watching VR content induced cybersickness. The SSQ score increased significantly after watching the VR content in both groups. The sensitive group showed significantly lower absolute power in the beta and gamma bands than the non-sensitive group. The cybersickness condition showed significantly increased delta and decreased alpha compared to the baseline condition. We evaluated EEG and SSQ to identify subjective symptoms and objective physiological changes associated with cybersickness.

Reliability Study of the Items of the Alberta Infant Motor Scale (AIMS) Using Kappa Analysis.

PURPOSE: We evaluated the interrater and intrarater reliabilities of the Korean version of the Alberta Infant Motor Scale (K-AIMS). METHODS: For the interrater reliability test, six raters participated in the K-AIMS evaluation using video clips of 70 infants (aged between 0 and 18 months). One rater participated in an intrarater reliability test. Among 70 infants, 46 were born preterm and 24 were born full term. A total of 58 AIMS items were evaluated for supine, prone, sitting, and standing positions. A reliability analysis was conducted using ICC and Fleiss' kappa. RESULTS: The highest Fleiss' kappa was found for the 4-7 months group for sitting (K = 0.701-1.000) and standing (K = 0.721-1.000), while the lowest K was the 3 months or under group for standing (K = 0.153-1.000). We found higher Fleiss' kappa statistics when all infants were evaluated without grouping for the three positions (K = 0.727-1.000), except standing (K = 0.192-1.000), for the interrater analysis. CONCLUSION: Our results demonstrate the good reliability for the Korean version of the AIMS for Korean infants (preterm and full term).

Modified desk height helps children with cerebral palsy perform sit-to-stand.

AIM: Children with cerebral palsy (CP) have difficulties performing activities that require the use of fundamental motor skills such as sit-to-stand (STS). In this study, we used a height adjustable chair and desk to investigate the role of desk support in STS and how it might benefit children with CP. METHODS: Seventeen typically developing children (TDC), average age = 9.7 years, and 28 children with CP (Gross Motor Function Classification System [GMFCS] I and II), average age = 10.3 years, participated in the test. Elapsed time and body sway were measured using a pressure mat and load cell while each child performed a STS task. Two different desk heights were tested for time consumption and sway under the condition of hands-on-desk and arms-crossed. RESULTS: We found that the elapsed time of hands-on-desk with the elbow flexion height was the shortest (p < 0.05). Sway amount was also significantly reduced for all children when they used the table for STS (p < 0.05). CONCLUSION: Results of this study may be a useful reference in rehabilitation training and designing a desk height beneficial for children with CP.Implications for RehabilitationBetter performance of sit-to-stand for a child with cerebral palsy could be made by a desk supportElapsed time during preparation period for sit-to-stand could be reduced by desk support for all CP childrenSway amount during sit-to-stand could be reduced by desk support, especially for the CP children with GMFCS level IIDesk height is an important parameter and should be studied in detail.

Test-retest reliability of the virtual reality sickness evaluation using electroencephalography (EEG).

No reliable quantitative and objective measurement method for virtual reality (VR) sickness has been firmly established to date. Electroencephalography (EEG) may be a strong candidate to evaluate VR sickness objectively. However, no test-retest evaluation has been made for VR sickness using EEG. To recruit VR sickness-sensitive participants, we tested 858 participants (age = 20's-50's) using the Motion Sickness Susceptibility Questionnaire (MSSQ). Among them, we recruited 21 males (average age = 25.0) who obtained the 75th percentile of scores on the MSSQ (32.9 ± 5.7). VR sickness was evaluated twice (one week apart) using EEG with VR video content designed to cause VR sickness. A Simulation Sickness Questionnaire (SSQ) was also used to evaluate VR sickness. In terms of the reliability of EEG, ICC and Cronbach's alpha analyses showed that three waves (delta, theta, and alpha) were consistent in two areas (frontal and central). A significant difference in EEG was also found repeatedly between the baseline and VR sickness (delta, theta, and alpha) in two areas (frontal and central). We evaluated EEG for its reliability and found specific waves and areas that showed good consistency and significant changes associated with VR sickness. These findings may support further research of VR sickness evaluation.

Quantitative Evaluation of Post-stroke Spasticity Using Neurophysiological and Radiological Tools: A Pilot Study.

OBJECTIVE: To determine the possibility of a new measurement tool using electromyography and ultrasonography for quantitative spasticity assessment in post-stroke patients. METHODS: Eight hemiplegic stroke patients with ankle plantarflexor spasticity confirmed by a Modified Ashworth Scale (MAS) were enrolled. Spasticity was evaluated using the MAS and Modified Tardieu Scale (MTS). Each subject underwent surface electromyography (sEMG) using the Brain Motor Control Assessment (BMCA) protocol and was compared with a healthy control group. Using ultrasonography, muscle architecture and elasticity index were measured from the medial gastrocnemius muscle (GCM) on the affected and unaffected sides. RESULTS: MAS and MTS revealed significant correlation with sEMG activity. The fascicle length and pennation angle were significantly decreased in the medial GCM on the hemiplegic side compared with the unaffected side. The elasticity index of the spastic medial GCM was significantly increased compared with the unaffected side. The MTS X and R2-R1 values were significantly correlated with the elasticity index in the hemiplegic GCM. The relationship between clinical evaluation tools and both BMCA and sonoelastography was linear, but not statistically significant in the multiple regression analysis. CONCLUSION: The BMCA protocol and ultrasonographic evaluation provide objective assessment of post-stroke spasticity. Further studies are necessary to conduct accurate assessment and treatment of spasticity.

Development of a simulator for the validation of noninvasive blood pressure-monitoring devices.

This research aimed to develop a simulator capable of oscillometric pressure pulses recorded from the participants for the validation of oscillometric noninvasive blood pressure (NIBP) devices. The simulator generates the pressure pulses to the cuff connected to NIBP devices depending on the oscillometric waveforms obtained from the participants. Device readings were compared with auscultatory references (systolic and diastolic blood pressures) of the participants. A total of 94 oscillometric waveforms from participants were used in the simulator for the validation of two automated NIBP devices (Omron HEM-7221 and UA-787Plus). For Omron HEM-7221, the differences between device readings and auscultation references for systolic and diastolic blood pressures were 2.82±7.27 and -4.74±6.73 mmHg, respectively. UA-787Plus showed differences of 3.26±5.69 and -3.53±6.61 mmHg, respectively. Although the number of individual measurements did not fulfill the ISO 81060-2 requirement for clinical validation, criterion 1, where the average of the difference and SD should be lower than ±5 and -8 mmHg, was fulfilled. Although the simulator still needs extensive comparative studies to be verified, it could be a potential candidate for a simple and robust tool for the validation and quality control of NIBP devices.

Usefulness of magnetocardiogram to detect unstable angina pectoris and non-ST elevation myocardial infarction.

Electrophysiologic information as well as anatomic information to detect coronary artery disease is important for accurate diagnosis. A diagnostic tool that can detect patients with unstable angina pectoris (UAP) or non-ST elevation myocardial infarction (NSTEMI) with severe stenosis would be beneficial for patients and clinicians. Magnetocardiography has been recognized as a noncontact, noninvasive, fast tool to detect ischemic coronary artery disease and provide direct electrophysiologic information from the heart. In this study, 10 magnetocardiographic (MCG) parameters from 4 groups, including 185 young controls, 19 age-matched controls (AMCs), 110 patients with UAP, and 83 patients with NSTEMIs, were analyzed. A 64-channel MCG system in a magnetically shielded room was used. All 10 parameters showed significant differences (p <0.001) between controls and patients with NSTEMIs, and 6 parameters showed significant differences (p <0.01) between AMCs and patients with UAP. MCG parameters significantly increased when ischemic heart conditions worsened. Of the 10 parameters, the magnetic field map was among the easiest ways to detect the severity of coronary artery disease. Abnormal magnetic field maps were observed frequently with worsening ischemic coronary artery disease (70% of patients with UAP and 92.5% of those with NSTEMIs had abnormal maps). The combination of the binary boundaries of the 10 parameters had 96.4% sensitivity and 85% specificity to detect NSTEMI. In conclusion, the MCG parameters and magnetic field maps may detect UAP and NSTEMI easily when they are considered together.

Magnetic dispersion of the late repolarization in Brugada syndrome.

BACKGROUND: Magnetocardiography (MCG) is a new noninvasive modality for recording cardiac depolarization and repolarization and was used in the present study to evaluate abnormalities in patients with Brugada syndrome (BS). METHODS AND RESULTS: The MCG findings of 10 BS, 21 right bundle branch block (RBBB), and 34 normal patients were compared. On the horizontal spatiotemporal activation graph (STAG), the r' waves were more frequently located on the right side in the RBBB than in the normal (p=0.001) or BS groups (p=0.001). The maximum current angles of the r' wave fell into the northwest axis in all BS patients as compared to having a right axis deviation in 19 of 21 RBBB patients (90.4%, p=0.001). In the magnetic field and current density vector maps during late repolarization, the BS group had a non-dipole pattern more frequently and a higher number of poles compared with the normal (p=0.001) and RBBB groups (p=0.001). CONCLUSIONS: During depolarization, the horizontal STAG location and maximum current angle of the r' wave were beneficial in differentiating BS from RBBB and normal. The magnetic dispersion was a more frequently observed finding in BS patients than in RBBB and normal patients during late repolarization.

Can magnetocardiography detect patients with non-ST-segment elevation myocardial infarction?

BACKGROUND AND AIM: Magnetocardiography (MCG) has been proposed as a noninvasive diagnostic tool to risk-stratify patients with myocardial infarction (MI) and ischemia. The purpose of this study is to find the MCG parameters that are sensitive enough to detect the non-ST-segment elevation myocardial infarction (NSTEMI) patients. METHODS: MCG data were recorded and analyzed from 165 young controls (mean age = 27.2 +/- 9.0 years), 57 age-matched controls (mean age = 55.9 +/- 10.5 years) and 83 NSTEMI patients (mean age = 59.7 +/- 11.1 years). The MCG recordings were obtained using a 64-channel MCG system in a magnetically shielded room. Statistical analyses were performed for 24 parameters derived from QRS-, R-, T-wave, and ST-T period. Binary boundaries to detect NSTEMI patients out of control subjects were found using the receiver operating characteristic (ROC) curve for each parameter. RESULTS: Fifteen parameters showed a significant difference (P < 0.05 and P < 0.01) between NSTEMI and both of the control groups. For detection of NSTEMI, the angle of the maximum current and the filed map angle on T-wave peak showed the highest diagnostic performance from 75% to 92% including accuracy, sensitivity, specificity, positive predictive value, and negative predictive value (area under ROC curve = 0.87 approximately 0.93). CONCLUSIONS: Our study showed that MCG has potential clinical application for detection of NSTEMI and should be further investigated.

Reproducibility of quantitative estimate of magnetocardiographic ventricular depolarization and repolarization parameters in healthy subjects and patients with coronary artery disease.

Magnetocardiography (MCG) has been introduced as an innovative non-invasive diagnostic tool to identify various heart diseases. However, there have been little data on the reliability of MCG parameters. The purpose of this study is to examine the test-retest reliability of different diagnostic parameters derived from MCG. We investigated short-, intermediate-, and long-term reliability of nine parameters from T (max/3)-T (max) interval, and five parameters from each time point such as QRS-wave, the peak of R-, and T-wave were evaluated. Short-term reliability was tested in the youngest 20 subjects (mean age = 26.3 +/- 4.9 years) in three sessions separated by 5 min. Intermediate-term reliability was tested in the 35 subjects with coronary artery disease (CAD) (65.1 +/- 7.1 years) with two recording sessions each in the morning and afternoon, separated by more than four hours. Long-term reliability was tested in seven subjects (37.1 +/- 8.8 years) using seven daily sessions. Interclass correlation coefficients (ICC) showed that test-retest reliability was good to excellent (0.99 > or = ICC > or = 0.80) for six out of nine parameters within T (max/3)-T (max). In addition, all parameters on the peak of R-wave, T-wave, and QRS-wave integrated were good to excellent (0.99 > or = ICC > or = 0.80) except for one parameter of CAD patients showing lower ICC values under 0.7. In conclusion, our study showed that the test-retest characteristics of the studied MCG parameters are generally stable and reliable over periods of minutes to days in subjects with different age spectrums.

Reliability of surface electromyographic measurements from subjects with spinal cord injury during voluntary motor tasks.

In this study, the reliability of surface electromyographic data (root-mean-square) for volitional motor tasks drawn from a standardized protocol was assessed. For each motor task, 5 s epochs of data were analyzed with a new method to generate a measure called the voluntary response index (VRI). The VRI consists of two components, magnitude and similarity index (SI), that were separately analyzed for repeatability. We examined three repetitions of each of 10 volitional motor tasks in 69 subjects with spinal cord injury (American Spinal Injury Association [ASIA] Impairment Scale [AIS], classifications C and D: 34 AIS-C and 35 AIS-D) for short-term (within-day) reliability. In 6 of the 69 subjects (3 each, AIS-C and AIS-D), the entire study was repeated after 1 week and results were assessed for intermediate-term (1 week apart) reliability. The reliability of the method for voluntary motor tasks was assessed by intraclass correlation coefficient (ICC), analysis of variance, coefficient of variance, and Pearson's correlation. Good reliability was found for magnitude (ICC = 0.71-0.99, Pearson's r = 0.77-0.99) and for SI (ICC = 0.65-0.96, Pearson's r = 0.72-0.93) for three repeated tests (within-day). Significant difference was found for studies completed 1 week apart for magnitude (p = 0.02) but not for SI (p = 0.57). In addition, SI showed less variation than magnitude (p < 0.001). No significant difference of magnitude and SI between tasks was observed.

Analysis of sEMG during voluntary movement--Part II: Voluntary response index sensitivity.

In this paper, a method for analyzing surface electromyographic (sEMG) data recorded from the lower-limb muscles of incomplete spinal-cord injured (iSCI) subjects is evaluated. sEMG was recorded bilaterally from quadriceps, adductor, hamstring, tibialis anterior, and triceps surae muscles during voluntary ankle dorsiflexion performed in the supine position as part of a comprehensive motor control assessment protocol. Analysis of the sEMG centered on two features, the magnitude of activation and the degree of similarity [similarity index (SI)] of the sEMG distribution to that of healthy subjects performing the same maneuver (n = 10). The analysis calculations resulted in response vectors (RV) that were compared to healthy-subject-derived prototype response vectors resulting in a voluntary response index (VRI). Incomplete SCI subjects (n = 9) were used to test the sensitivity of this analysis method. They were given supported-weight treadmill ambulation training, which is expected to improve or at least not cause a deterioration of voluntary motor control. The VRI provided evidence that the quantitative sEMG analysis method used was able to differentiate between healthy subjects and those with iSCI, characterize individual differences among iSCI subjects, and track motor control changes occurring over time.