Eyes-closed Condition Research Articles

Self-Mobilization Exercise Program Improved Postural Stability in the Anterior-Posterior Direction with Eyes Closed

Maintenance of equilibrium is influenced by postural symmetry and deviations such as a forward head. An exercise program involving an effect such as self-joint mobilization was developed to address spinal curvature; however, its effect on postural stability is still unclear. The purpose of this study was to address to what extent the self-mobilization exercise program would influence postural sway while standing still. The Exercise group (n = 16) performed the self-mobilization while lying supine on a cylinder-shaped tube (98 cm length, 15 cm diameter), consisting of three warm-up positionings followed by seven motions. The Control group (n = 16) laid supine on a flat surface with their legs flexed. Before and immediately after respective interventions, the plantar center of pressure was quantified while subjects were standing with eyes open and closed. The results show the exercise group reduced the postural sway in the antero-posterior direction only during the eyes-closed condition. Neither exercise nor control groups showed a significant change in postural sway during the eyes-open condition. Our findings indicate the self-mobilization exercise program improved the participant’s stability when visual feedback was not reliable for postural control. The improved postural control in the antero-posterior direction may be accounted for by facilitated activation of planterflexors and dorsiflexors which are primary muscles in ankle strategy for postural control. Effects of this exercise program on postural stability appear to be direction dependent, which provide insight when healthcare professionals incorporate exercise programs for postural symmetry.

Effects of spaceflight on the EEG alpha power and functional connectivity

Electroencephalography (EEG) can detect changes in cerebral activity during spaceflight. This study evaluates the effect of spaceflight on brain networks through analysis of the Default Mode Network (DMN)'s alpha frequency band power and functional connectivity (FC), and the persistence of these changes. Five astronauts' resting state EEGs under three conditions were analyzed (pre-flight, in-flight, and post-flight). DMN’s alpha band power and FC were computed using eLORETA and phase-locking value. Eyes-opened (EO) and eyes-closed (EC) conditions were differentiated. We found a DMN alpha band power reduction during in-flight (EC: p < 0.001; EO: p < 0.05) and post-flight (EC: p < 0.001; EO: p < 0.01) when compared to pre-flight condition. FC strength decreased during in-flight (EC: p < 0.01; EO: p < 0.01) and post-flight (EC: ns; EO: p < 0.01) compared to pre-flight condition. The DMN alpha band power and FC strength reduction persisted until 20 days after landing. Spaceflight caused electrocerebral alterations that persisted after return to earth. Periodic assessment by EEG-derived DMN analysis has the potential to become a neurophysiologic marker of cerebral functional integrity during exploration missions to space.

Straight Jump Landing Position of Trampoline Gymnasts with Stable Occlusal Balance Reflects Standing Postural Control Function

The aim of this study was to clarify the relationship between the landing position during consecutive straight jumps and standing posture stability of trampoline gymnasts with stable occlusal balance. Participants were 10 healthy men (BMI: 18.5–25.0) and 10 trampoline gymnasts (competition experience: ≥12 years), all of whom had stable occlusal balance. To assess postural control function, the displacements in the forward–backward (COP-FB) and the left–right directions (COP-LR) of the center of foot pressure were recorded under eyes-open and eyes-closed conditions. For the trampoline gymnasts, landing positions during 10 consecutive straight jumps were recorded. The horizontal displacements from the center of the bed in the forward–backward (H-FB) and the left–right directions (H-LR) directions were recorded. Differences in COP displacement between participant groups and between visual conditions were analyzed, along with the correlations between COP displacement and landing position. COP-FB in the eyes-open condition was significantly smaller in trampoline gymnasts than in healthy men (p &lt; 0.05). Significant strong positive correlations were observed between COP-FB and H-FB, and between COP-LR and H-LR (p &lt; 0.05). The postural control function of trampoline gymnasts was superior to that of healthy men in the eyes-open condition. The landing position during straight jumps of trampoline gymnasts with stable occlusal balance reflects standing postural control function.

Older adults and stroke survivors are steadier when gazing down.

Advanced age and brain damage have been reported to increase the propensity to gaze down while walking, a behavior that is thought to enhance stability through anticipatory stepping control. Recently, downward gazing (DWG) has been shown to enhance postural steadiness in healthy adults, suggesting that it can also support stability through a feedback control mechanism. These results have been speculated to be the consequence of the altered visual flow when gazing down. The main objective of this cross-sectional, exploratory study was to investigate whether DWG also enhances postural control in older adults and stroke survivors, and whether such effect is altered with aging and brain damage. Posturography of older adults and stroke survivors, performing a total of 500 trials, was tested under varying gaze conditions and compared with a cohort of healthy young adults (375 trials). To test the involvement of the visual system we performed spectral analysis and compared the changes in the relative power between gaze conditions. Reduction in postural sway was observed when participants gazed down 1 and 3 meters ahead whereas DWG towards the toes decreased steadiness. These effects were unmodulated by age but were modulated by stroke. The relative power in the spectral band associated with visual feedback was significantly reduced when visual input was unavailable (eyes-closed condition) but was unaffected by the different DWG conditions. Like young adults, older adults and stroke survivors better control their postural sway when gazing down a few steps ahead, but extreme DWG can impair this ability, especially in people with stroke.

Static and Dynamic Imbalance in Patients with Breast Cancer-Related Lymphedema.

Background: Breast cancer-related lymphedema (BCRL) was associated with postural imbalance, but the immature knowledge introduced debate about which component of the balance was affected by BCRL in the literature. The aim of this study was to determine the static and dynamic balance of patients with BCRL in comparison with healthy subjects. Methods and Results: This case-control designed study recruited 30 BCRL patients and 30 healthy individuals. The demographic and clinical variables of the subjects were recorded. The static balance stability parameters on four conditions (eyes opened-stable ground, eyes closed-stable ground, eyes opened-unstable ground, eyes closed-unstable ground) and dynamic stability of all participants were evaluated. The values of both stable ground conditions were similar between the groups (p < 0.05). However, values of both eyes opened-unstable ground (p = 0.032) and eyes closed-unstable ground (p = 0.034) conditions were significantly impaired in BCRL in comparison with controls. Besides, comparison of sway area of the opened versus closed eyes conditions on unstable ground (p = 0.036), and movement speed while correcting the center of pressure on unstable ground (with opened and closed eyes, p = 0.014 and p = 0.004 respectively) revealed increased values in the BCRL group. Likewise, the dynamic stability was significantly disrupted in the BCRL group (p = 0.043). Conclusion: Closing eyes did not affect the postural balance in patients with BCRL, whereas the deterioration of ground altered the balance significantly in the BCRL group compared with healthy subjects. We suggest the inclusion of balance exercises and guidance for selection of correct shoes and insoles in routine lymphedema rehabilitation program.

Trend Change Analysis as a New Tool to Complement the Evaluation of Human Body Balance in the Time and Frequency Domains.

Trend change analysis is a tool that complements the assessment of human body stability and provides information on the number and frequency of postural corrections during an examination. The present research aims to determine the possibility of using this method of analysis to investigate postural stability during tests of standing with open eyes (OE) and closed eyes (CE). A total of 118 participants (67 females, 51males) aged 23 (SD 1.3) were assessed. Tests involved standing on a stabilographic platform for 50 s. Trend change analysis was used to evaluate displacement values of the center of pressure (COP). Values for the COP courses as well as values associated with trend change analysis, such as: TCI, MACD_t and MACD_V were determined. Histograms of distribution were plotted for TCI values. The present study provides information on alterations of the strategy used for maintaining balance, which are associated with the number of postural corrections and COP displacement between corrections for measurements taken during the standing test with CE in relation to OE measurements. The strategy demonstrated an ability to detect a smaller number of quick corrections, an increased number of corrections of longer duration, and the elongation of displacement between subsequent postural corrections. Slight standard deviations in TCI and MACD_t values calculated during trend change analysis, for both the OE and CE conditions, made it possible to classify these values as indexes of postural stability with significant sensitivity to slight changes.

A Standing Low-frequency Vibration Exercise Device for Improving Balance in Community-dwelling Older Adults: A Single-blind Randomized Controlled Trial.

This study aimed to compare the effects of the standing low-frequency vibration exercise device (SLVED) and walking training on balance ability on an unstable surface in community-dwelling elderly people. Thirty-eight older adults were randomly allocated to the SLVED sessions: the intervention group (n = 19), and the walking sessions: the control group (n = 19). Each group session lasted 20 min and was performed twice a week for 12 weeks. Standing balance was assessed by the change in center-of-gravity sway of the participant standing on foam rubber with eyes open (EO) and eyes closed (EC). The primary outcome measures were the root mean square (RMS) values of the center of foot pressure in the mediolateral and anteroposterior directions and the RMS area. Secondary outcome measures were the results of the 10-m walking time test (10 MWT), five-times sit-to-stand (5T-STS) test, and timed up-and-go (TUG) test. Analysis of variance showed a significant group × time interaction for the TUG test. Significant improvements were observed in Y-RMS for EO condition; RMS, X-RMS, Y-RMS, and RMS area for EC condition; and 10 MWT, 5T-STS test, and TUG test for the main effect of the time factor. SLVED for intervention in community-dwelling older adults showed a greater improvement than walking training in the TUG test. In addition, SLVED improved the Y-RMS for the EO condition on foam rubber; RMS, X-RMS, Y-RMS, and RMS area for the EC condition on foam rubber in standing balance; and the 10 MWT and 5T-STS test, suggesting that it has similar effects to walking training.

Does the patellar tendon reflex affect the postural stability in stroke patients with blocked vision?

Stroke patients often show postural instability. The patellar tendon reflex is a basic physical examination for stroke patients. This study aimed to explore the correlation between patellar tendon reflex grade and postural stability among stroke patients. A total of 37 elderly stroke patients, each with the same quadriceps muscle strength but different patellar tendon reflex levels, were tested on a force platform under eyes-open (EO) and eyes-closed (EC) conditions. Parametric analysis, detrended fluctuation analysis (DFA), and power spectral density (PSD) analysis were used in centre of pressure (COP) signal processing. The correlation between the results of measured data processing and the level of patellar tendon reflex was analysed. All three parameters of COP (the length of the sway trajectory, the mean range of the sway trajectory in the mediolateral [ML] direction [R x ], and the mean range of the sway trajectory in the anterior-posterior [AP] directions [R y ]) were negatively correlated with the patient's patellar tendon reflex grade under the EC condition. The DFA results showed that a higher grade of patellar tendon reflex was associated with a smaller value of the crossover point in the AP direction. Only the PSD values of each frequency band in the AP direction were negatively correlated with patellar tendon reflex grade with EO and became negatively correlated in both AP and ML directions with EC. Overall, the results showed a strong correlation between patellar tendon reflex and postural stability in stroke patients when vision was blocked. The strong correlation with EC may provide insights into clinic evaluation and treatment for rehabilitation or fall risks of stroke patients.

Effects of foot preference on postural control in soccer players

A soccer player often uses the dominant leg during activities and the non-dominant leg is used to support body weight. This may have different effects on the postural control between the dominant and non-dominant legs in soccer players. Detection of a possible asymmetry in postural control is important because a bilateral difference may be a contributing factor to injury. This study aimed to compare the postural control performances of right- and left-footed amateur soccer players; secondly, it aimed to address the postural control differences between the dominant and non-dominant legs of soccer players. Twenty-four healthy male soccer players were divided into two different groups (right foot dominant = 12, left foot dominant = 12). Dynamic postural control scores of soccer players in dominant and non-dominant single-stances were measured under two sensory conditions (eyes open and eyes closed) using the Biodex Balance System. In the comparison of two independent groups according to the normality distribution, the t-test and Mann-Whitney U test were used for independent samples. The t-test for dependent samples and the Wilcoxon test were used to compare dependent groups. The results of the study; whether the players are right-footed or left-footed in both eye-open and eye-closed conditions does not affect their postural control performance; showed that the postural control performance of the dominant leg was higher than the non-dominant leg in the eye-open condition of all soccer players regardless of right and left legs. Therefore, it was determined that leg dominance exhibited a symmetrical performance in terms of postural control.

A comparison of resting-state eyes-closed and dark-room alpha-band activity in children.

In a relaxed and awake state with the eyes closed, 8-12 Hz neural oscillations are the dominant rhythm, most prominent in parietal-occipital regions. Resting-state (RS) alpha is associated with processing speed and is also thought to be central to how networks process information. Unfortunately, the RS eyes-closed (EC) exam can only be used with individuals who can remain awake with their eyes closed for an extended period. As such, infants, toddlers, and individuals with intellectual disabilities are usually excluded from RS alpha studies. Previous research suggests obtaining RS alpha measures in a dark room with the eyes open as a viable alternative to the traditional RS EC exam. To further explore this, RS EC and RS dark room (DR) eyes-open alpha activity was recorded using magnetoencephalography in children with typical development (TD; N = 37) and children with autism spectrum disorder (ASD; N = 30) 6.9-12.6 years old. Findings showed good reliability for the RS EC and DR peak alpha frequency (frequency with strongest alpha power; interclass correlation (ICC) = 0.83). ICCs for posterior alpha power were slightly lower (ICCs in the 0.70 s), with an ~ 5% reduction in posterior alpha power in the DR than EC condition. No differences in the EC and DR associations were observed between the TD and ASD groups. Finally, age was associated with both EC and DR peak alpha frequency. Findings thus indicate the DR exam as a viable way to obtain RS alpha measures in populations frequently excluded from electrophysiology RS studies.

Frontal midline theta rhythm and gamma activity measured by sheet-type wearable EEG device.

The current study measured the frontal midline theta rhythm (Fmθ), which appears in the frontal midline region during the attentional focus state, using the sheet-type wearable electroencephalograph (EEG) device HARU-1, and examined the modulation of frontal gamma band activity by cognitive tasks. We measured the frontal EEG of 20 healthy subjects using HARU-1 for 2 min during the rest eyes-closed condition and simple mental calculation task condition, respectively. Statistical analyses were conducted using permutation testing based on t-test and cluster analysis to compare the results between the resting state and the task condition. Twelve of 20 subjects showed Fmθ during the task condition. The 12 subjects with Fmθ showed significantly higher activity of the theta and gamma bands, and significantly low activity of the alpha band during the task condition compared to the resting condition. In the eight subjects without Fmθ were significantly low activity of the alpha and beta bands and no significant activity in the theta and gamma band activity during the task condition compared to the resting condition. These results indicate that it is possible to measure Fmθ using HARU-1. A novel finding was the gamma band activity appearing with Fmθ in the left and right frontal forehead regions, suggesting that it reflects the function of the prefrontal cortex in working memory tasks.

Lower extremity proprioception and its association with activity and participation in children with unilateral spastic cerebral palsy

ObjectiveThis cross-sectional study aimed to assess lower extremity proprioception and investigate its relationship to activity and participation levels in children with unilateral spastic cerebral palsy (USCP). MethodsA total of 22 children with USCP between the ages of 5 and 16 years participated in this study. Lower extremity proprioception was evaluated with a protocol that consisted of verbal and location identification, unilateral and contralateral limb matching, and static and dynamic balance tests performed with the impaired and less impaired lower extremities under eyes-open and eyes-closed conditions. Furthermore, the Functional Independence Measure (WeeFIM) and Pediatric Outcomes Data Collection Instrument (PODCI) were used to evaluate the independence levels in daily living activities and participation levels. ResultsChildren demonstrated proprioceptive loss, as evidenced by an increase in matching errors under the eyes-closed condition compared to the eyes-open condition (p<0.05). Also, the impaired extremity had greater proprioceptive loss than the less impaired extremity (p<0.05). The 5–6-year age group experienced greater proprioceptive deficits than did the 7–11 and 12–16 age groups (p<0.05). Children's lower extremity proprioceptive deficit was moderately associated with their activity and participation levels (p<0.05). ConclusionsOur findings suggest that treatment programs based on comprehensive assessments, including proprioception, may be more effective in these children.

Persistent impacts of smoking on resting-state EEG in male chronic smokers and past-smokers with 20 years of abstinence

Smoking is a severe addictive health risk behavior and notorious for the high likelihood of relapse after attempted cessation. Such an addictive pattern in smoking has been associated with neurobiological changes in the brain. However, little is known whether the neural changes associated with chronic smoking persist after a long period of successful abstinence. To address this question, we examined resting state EEG (rsEEG) in chronic smokers who have been smoking for 20 years or more, past-smokers who have been successfully abstaining for 20 years or more, and never-smokers. Both current-smokers and past-smokers showed significantly decreased relative theta power than never-smokers, showcasing persistent effect of smoking on the brain. Other rsEEG features in alpha frequency band demonstrated distinctive patterns associated with active smoking, such that compared to never-smokers, only current-smokers, but not past-smokers, showed significantly higher relative power, EEG reactivity—power changes between eyes-closed and eyes-open conditions—, and coherence between channels. Furthermore, individual variabilities across these rsEEG biomarkers were accounted for by individuals’ self-reported smoking history and nicotine dependence in current- and past- smokers. These data suggest the persistent effect of smoking on the brain even after sustained remission for 20 years.

Brain Wave Patterns in Patients With Chronic Low Back Pain: A Case-control Study.

Research evidence indicates that maladaptive reorganization of the brain plays a critical role in amplifying pain experiences and pain chronification; however, no clear evidence of change exists in brain wave activity among patients with chronic low back pain (CLBP). The objective of this study was to assess brain wave activity in patients with CLBP, compared to healthy controls. Twenty-five patients with CLBP and twenty-four healthy controls participated in the study. A quantitative electroencephalography device was used to assess brain wave activity in eyes-open and eyes-closed (EO and EC) conditions. The regional absolute and relative power of brain waves were compared between the groups. Our results showed a significant increase in the absolute power of theta (F=5.905, P=0.019), alpha (F=5.404, P=0.024) waves in patients with CLBP compared to healthy subjects in both EC and EO conditions. Patients with CLBP showed a reduced delta absolute power in the frontal region (F=5.852, P=0.019) and augmented delta absolute power in the central region (F=5.597, P=0.022) in the EO condition. An increased delta absolute power was observed in the frontal (F=7.563 P=0.008), central (F=10.430, P=0.002), and parietal (F=4.596, P=0.037) regions in patients with CLBP compared to the healthy subjects in the EC condition. In the EC condition, significant increases in theta relative power (F=4.680, P=0.036) in the parietal region were also found in patients with CLBP. The increased absolute power of brain waves in people with CLBP may indicate cortical overactivity and changes in the pain processing mechanisms in these patients. Chronic low back pain (CLBP) increases the alpha, theta, and delta power in the brain.CLBP is associated with increased brain wave activity in the frontal, central, and parietal regions.Our findings suggest altered central pain processing in CLBP. Traditional diagnosis and treatment of CLBP are mainly focused on peripheral pathology. But, the modern neuroscience approach to pain highlights the role of cortical plasticity in chronic musculoskeletal pain. In this regard, several studies found structural and functional changes in the brain in patients with chronic pain. Detailed knowledge about cortical changes in CLBP can improve our understanding of mechanisms involved in CLBP, opening a new window to better treatment of LBP (Low back pain). This study investigated brain wave activity in patients with CLBP compared to healthy individuals. Our findings suggest increased brain activity in various parts of the brain in patients with chronic LBP. This finding indicates that CLBP treatment should focus on both peripheral and cortical factors rather than local tissue damage.

Differential Cortical Oscillatory Patterns in Amputees With and Without Phantom Limb Pain.

Phantom limb pain (PLP) as neuropathic pain affects the life of amputees. It is believed an efficient PLP treatment should consider the underlying neurological mechanisms. Hereby, we investigated brain activity in PLP and its relationships to the psychological and cognitive dimensions of chronic pain. We investigate differences in resting brain activities between amputees with and without pain. We hypothesize significant differences in the motor cortex and parietal cortex activity that are related to pain perception. Also, we hypothesize two groups have significant differences in cognitive and psychological components. Behavioral assessment (psychological status, life satisfaction, and pain level) and EEG signals of 19 amputees (12 without pain and 7 with pain) were recorded. Data were statistically compared between the two groups. Also, the association between behavioral and neurophysiological data was computed. The results showed a significant decrease in the pain group for the beta and gamma waves, as well as, for the theta and delta waves in the posterior temporal on both sides, during the eye-open condition. The eyes-closed condition showed that the delta waves were decreased on the right side of the cortex. Also, data showed a significant difference in the correlation of pain features with brain waves between the two groups. Significant differences were mostly observed in regions related to pain perception rather than the motor cortex. This can be due to the learned strategies to deal with pain and the degree of pain. Results showed maladaptive cognitive processes had a relationship with brain wave activities. According to the result of brain wave activities, it seems that cognitive factors have a role in the experience of PLP rather than neuroplasticity through amputation. Differences found in the parietal and temporal regions of phantom limb pain's (PLP's) suggests cognition's role in the persistence of PLP.Decreased delta power at the posterior temporal cortex in PLP's could be the focus of treatments.Increased activity of the parietal cortex could be helpful in the treatment of PLP's. PLP is an annoying neurologic pain. A wide range of treatments have focused on this type of pain but couldn't be effective. Recently, researchers suggest BCI-based treatments for better treatment. For this type of treatment, we should know the neurological aspect of PLP. In most studies to investigate or treatment of neurological aspects of PLP, researchers induced pain experimentally or studied acute phantom limb pain. We believed for a better understanding of PLP, should investigate it in a natural and stabilized position. Therefore we studied brain activities in amputees with and without PLP in a resting state to find out differences. Trends in this field express the alpha band differences in the motor cortex. On the contrary, our results showed the most significant difference in high-frequency bandpasses such as beta and gamma. Also, in our study, it seems the parietal and temporal cortex that are related to pain perception is the more relevant to PLP. This study showed a psycho-cognitive aspect of pain such as pain exaggeration has a relation with PLP's brain wave activities. So, we can suggest rather than neuroplasticity through amputation, cognitive factors have a role in the experience of PLP.

Characterization of Balance Control and Postural Stability in Patients With Alzheimer Disease.

Balance in Alzheimer disease (AD) patients is not rigorously understood. In this study, we characterize balance using qualitative [Berg Balance Scale (BBS)] and quantitative measures (posturography) and assess relationships between qualitative and quantitative balance measures in AD. Patients with mild-moderate AD (n=48) were recruited. BBS scores and posturography metrics, including medial-lateral sway range, anterior-posterior sway range, sway area, and sway velocity, were assessed in eyes-open and eyes-closed conditions. Adjusted linear regressions were used to assess relationships between posturography and BBS score. Mean BBS score was 50.4±5.3. In eyes-open conditions, posturography and BBS score were not significantly associated. In eyes-closed conditions, better BBS score was significantly associated with lower sway area (β=-0.91; P =0.006). Better scores of BBS items involving turning and reduced base of support were associated with greater eyes-closed sway area. Posturography in the more challenging eyes-closed condition may predict functional balance deficits in AD patients.

The effect of musk incense stick aroma inhalation on different features of electroencephalogram signals and working memory for use in neurofeedback training

Susceptibility of brain activity to the inhalation of different aromas established the idea of inhaling an aroma as an auxiliary factor in neurofeedback training. The present study has focused on investigating the effect of musk incense stick aroma inhalation on various features of EEG signals (power of different frequency bands along with Katz fractal dimension (Katz’s FD), approximate entropy (ApEn) and scaling exponent) and working memory for use in neurofeedback training. To raise this aim, the EEG signals were recorded under eyes-open (EO) and eyes-closed (EC) conditions for 22 healthy subjects before and during the musk incense stick aroma inhalation, followed by performing Wechsler Memory Scale (WMS). The results showed that musk incense stick aroma inhalation under EO condition increased the relative power of delta, theta, sensorimotor rhythm (SMR) and low beta frequency bands along with ApEn and Katz’s FD in most channels, whereas decreased the relative power of alpha, high beta and gamma bands. A decrease was found in the relative power of delta, theta, SMR, low beta, high beta and gamma frequency bands in some channels under EC conditions. ApEn and Katz’s FD values also increased in most channels under EC conditions following musk incense stick aroma inhalation. The scaling exponent also decreased under the same conditions in most channels. However, these changes were not significant in all channels. The WMS score also increased after inhaling aroma, but not significantly. The findings of this research suggest the use of musk incense stick aroma inhalation during neurofeedback training to increase training efficiency.

Neuromodulatory feasibility of a current limiter-based tDCS device: a resting-state electroencephalography study.

Recently, we introduced a current limiter-based novel transcranial direct-current stimulation (tDCS) device that does not generate significant tDCS-induced electrical artifacts, thereby facilitating simultaneous electroencephalography (EEG) measurement during tDCS application. In this study, we investigated the neuromodulatory effect of the tDCS device using resting-state EEG data measured during tDCS application in terms of EEG power spectral densities (PSD) and brain network indices (clustering coefficient and path length). Resting-state EEG data were recorded from 10 healthy subjects during both eyes-open (EO) and eyes-closed (EC) states for each of five different conditions (baseline, sham, post-sham, tDCS, and post-tDCS). In the tDCS condition, tDCS was applied for 12min with a current intensity of 1.5 mA, whereas tDCS was applied only for the first 30s in the sham condition. EEG PSD and brain network indices were computed for the alpha frequency band most closely associated with resting-state EEG. Both alpha PSD and network indices were found to significantly increase during and after tDCS application compared to those of the baseline condition in the EO state, but not in the EC state owing to the ceiling effect. Our results demonstrate the neuromodulatory effect of the tDCS device that does not generate significant tDCS-induced electrical artifacts, thereby allowing simultaneous measurement of electrical brain activity. We expect our novel tDCS device to be practically useful in exploring the impact of tDCS on neuromodulation more precisely using ongoing EEG data simultaneously measured during tDCS application.

Directed brain network analysis in anxious and non-anxious depression based on EEG source reconstruction and graph theory

Patients with anxious depression have more severe symptoms, more side effects, and higher resistance to treatment than patients with non-anxious depression; therefore, it is crucial to clarify the differences between these two types of patients. In this study, a 5-minute resting EEG was recorded in 15 patients with anxious depression and 9 patients with non-anxious depression under eyes open and closed conditions. Sixty-eight subcortical regions were extracted using exact low resolution brain electromagnetic tomography (eLORETA). The directed transfer function was then used to construct brain networks. Specific features based on graph theory including the strength of connectivity and betweenness centrality (BC) were calculated from the networks. Finally, significant features were selected using the Mann-Whitney U test, and patients were classified into anxious and non-anxious depressive groups using the Support Vector Machine (SVM). Results showed that features of outward connectivity strength led to the highest accuracy, F-score, and specificity with 91.66%, 87. 5%, and 100% in the eyes-closed state, respectively. Moreover, we found that the strength of connectivity in both directions increased for the anxious depressive group during the eyes-open state. In particular, higher outward connectivity was observed in the right hemisphere for the anxious depressive group. Further findings also revealed that features with the most significant difference were mainly associated with the beta band. In addition, significant increased inward and outward connectivity and decreased nodal centrality were observed in the posterior regions of the default mode network. These preliminary findings might provide new insights into the recognition of anxious depressed patients.

Automatic characterization of stroke patients’ posturography based on probability density analysis

ObjectiveThe probability density analysis was applied to automatically characterize the center of pressure (COP) data for evaluation of the stroke patients’ balance ability.MethodsThe real-time COP coordinates of 38 stroke patients with eyes open and closed during quiet standing were obtained, respectively, from a precision force platform. The COP data were analyzed and characterized by the commonly used parameters: total sway length (SL), sway radius (SR), envelope sway area (EA), and the probability density analysis based parameters: projection area (PA), skewness (SK) and kurtosis (KT), and their statistical correlations were analyzed. The differences of both conventional parameters and probability density parameters under the conditions of eyes open (EO) and eyes closed (EC) were compared.ResultsThe PA from probability density analysis is strongly correlated with SL and SR. Both the traditional parameters and probability density parameters in the EC state are significantly different from those in the EO state. The obtained various statokinesigrams were calculated and categorized into typical sway types through probability density function for clinical evaluation of the balance ability of stroke patients.ConclusionsThe probability density analysis of COP data can be used to characterize the posturography for evaluation of the balance ability of stroke patients.