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Using a wireless single channel EEG device, we investigated the feasibility of using short-term frontal EEG as a means to evaluate the dynamic changes of mental workload. Frontal EEG signals were recorded from twenty healthy subjects performing four cognitive and motor tasks, including arithmetic operation, finger tapping, mental rotation and lexical decision task. Our findings revealed that theta activity is the common EEG feature that increases with difficulty across four tasks. Meanwhile, with a short-time analysis window, the level of mental workload could be classified from EEG features with 65%-75% accuracy across subjects using a SVM model. These findings suggest that frontal EEG could be used for evaluating the dynamic changes of mental workload.

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This paper presents an investigation into the cortico-muscular relationship during a grasping task by evaluating the information transfer between EEG and EMG signals. Information transfer was computed via a non-linear model-free measure, transfer entropy (TE). To examine the cross-frequency interaction, TEs were computed after the times series were decomposed into various frequency ranges via wavelet transform. Our results demonstrate the capability of TE to capture the direct interaction between EEG and EMG. In addition, the cross-frequency analysis revealed instantaneous decrease in information transfer from EEG to the high frequency component of EMG (100-200Hz) during the onset of movement.

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OBJECTIVE: Brain-computer interfaces (BCIs) aimed at restoring communication to people with severe neuromuscular disabilities often use event-related potentials (ERPs) in scalp-recorded EEG activity. Up to the present, most research and development in this area has been done in the laboratory with young healthy control subjects. In order to facilitate the development of BCI most useful to people with disabilities, the present study set out to: (1) determine whether people with amyotrophic lateral sclerosis (ALS) and healthy, age-matched volunteers (HVs) differ in the speed and accuracy of their ERP-based BCI use; (2) compare the ERP characteristics of these two groups; and (3) identify ERP-related factors that might enable improvement in BCI performance for people with disabilities. METHODS: Sixteen EEG channels were recorded while people with ALS or healthy age-matched volunteers (HVs) used a P300-based BCI. The subjects with ALS had little or no remaining useful motor control (mean ALS Functional Rating Scale-Revised 9.4 (±9.5SD) (range 0-25)). Each subject attended to a target item as the items in a 6×6 visual matrix flashed. The BCI used a stepwise linear discriminant function (SWLDA) to determine the item the user wished to select (i.e., the target item). Offline analyses assessed the latencies, amplitudes, and locations of ERPs to the target and non-target items for people with ALS and age-matched control subjects. RESULTS: BCI accuracy and communication rate did not differ significantly between ALS users and HVs. Although ERP morphology was similar for the two groups, their target ERPs differed significantly in the location and amplitude of the late positivity (P300), the amplitude of the early negativity (N200), and the latency of the late negativity (LN). CONCLUSIONS: The differences in target ERP components between people with ALS and age-matched HVs are consistent with the growing recognition that ALS may affect cortical function. The development of BCIs for use by this population may begin with studies in HVs but also needs to include studies in people with ALS. Their differences in ERP components may affect the selection of electrode montages, and might also affect the selection of presentation parameters (e.g., matrix design, stimulation rate). SIGNIFICANCE: P300-based BCI performance in people severely disabled by ALS is similar to that of age-matched control subjects. At the same time, their ERP components differ to some degree from those of controls. Attention to these differences could contribute to the development of BCIs useful to those with ALS and possibly to others with severe neuromuscular disabilities.

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Brain-computer interfaces (BCIs) might restore communication to people severely disabled by amyotrophic lateral sclerosis (ALS) or other disorders. We sought to: 1) define a protocol for determining whether a person with ALS can use a visual P300-based BCI; 2) determine what proportion of this population can use the BCI; and 3) identify factors affecting BCI performance. Twenty-five individuals with ALS completed an evaluation protocol using a standard 6 × 6 matrix and parameters selected by stepwise linear discrimination. With an 8-channel EEG montage, the subjects fell into two groups in BCI accuracy (chance accuracy 3%). Seventeen averaged 92 (± 3)% (range 71-100%), which is adequate for communication (G70 group). Eight averaged 12 (± 6)% (range 0-36%), inadequate for communication (L40 subject group). Performance did not correlate with disability: 11/17 (65%) of G70 subjects were severely disabled (i.e. ALSFRS-R < 5). All L40 subjects had visual impairments (e.g. nystagmus, diplopia, ptosis). P300 was larger and more anterior in G70 subjects. A 16-channel montage did not significantly improve accuracy. In conclusion, most people severely disabled by ALS could use a visual P300-based BCI for communication. In those who could not, visual impairment was the principal obstacle. For these individuals, auditory P300-based BCIs might be effective.

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This study investigates the modulation of frontal EEG dynamics with respect to progress in motor skill acquisition using a wireless EEG system with a single dry sensor. Participants were required to complete repeated trials of a computerized visual-motor task similar to mirror drawing while the EEG was collected. In each trial, task performance of the participants was summarized with a familiarity index which took into account the performance accuracy, completion rate and time. Our findings demonstrated that certain EEG power spectra decreased with an increase in motor task familiarity. In particular, frontal EEG activities in delta and theta bands of the whole trial and in gamma band in the middle of the trial are having a significant negative relationship with the overall familiarity level of the task. The findings suggest that frontal EEG spectra are significantly modulated during motor skill acquisition. Results of this study shed light on the possibility of simultaneous monitoring of brain activity during an unconstrained natural task with a single dry sensor mobile EEG in an everyday environment.

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This study investigates the modulation of frontal EEG dynamics with respect to progress in motor learning. Using a computerized visual-motor task similar to mirror drawing, our work demonstrated that overall EEG activities in all frequency bands decreased with an increase in motor task familiarity. In particular, frontal EEG activities in delta band of the whole trial and gamma band at the beginning of each trial are having a significant negative relationship with the overall familiarity level of the task. The findings suggest that frontal EEG spectra are significantly modulated during motor skill acquisition.

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The purpose of this study was to identify electroencephalography (EEG) features that correlate with P300-based brain-computer interface (P300 BCI) performance in people with amyotrophic lateral sclerosis (ALS). Twenty people with ALS used a P300 BCI spelling application in copy-spelling mode. Three types of EEG features were found to be good predictors of P300 BCI performance: (1) the root-mean-square amplitude and (2) the negative peak amplitude of the event-related potential to target stimuli (target ERP) at Fz, Cz, P3, Pz, and P4; and (3) EEG theta frequency (4.5-8 Hz) power at Fz, Cz, P3, Pz, P4, PO7, PO8 and Oz. A statistical prediction model that used a subset of these features accounted for >60% of the variance in copy-spelling performance (p < 0.001, mean R(2) = 0.6175). The correlations reflected between-subject, rather than within-subject, effects. The results enhance understanding of performance differences among P300 BCI users. The predictors found in this study might help in: (1) identifying suitable candidates for long-term P300 BCI operation; (2) assessing performance online. Further work on within-subject effects needs to be done to establish whether P300 BCI user performance could be improved by optimizing one or more of these EEG features.

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This study aimed at developing a method for automated electrocardiography (ECG) artifact detection and removal from trunk electromyography signals. Independent Component Analysis (ICA) method was applied to the simulated data set of ECG-corrupted surface electromyography (SEMG) signals. Independent Components (ICs) correspond to ECG artifact were then identified by an automated detection algorithm and subsequently removed. The detection performance of the algorithm was compared to that by visual inspection, while the artifact elimination performance was compared with Butterworth high pass filter at 30 Hz cutoff (BW HPF 30). The automated ECG-artifact detection algorithm successfully recognized the ECG source components in all data sets with a sensitivity of 100% and specificity of 99%. Better performance indicated by a significantly higher correlation coefficient (p<0.001) with the original EMG recordings was found in the SEMG data cleaned by the ICA-based method, than that by BW HPF 30. The automated ECG-artifact removal method for trunk SEMG recordings proposed in this study was demonstrated to produce a very good detection rate and preserved essential EMG components while keeping its distortion to minimum. The automatic nature of our method has solved the problem of visual inspection by standard ICA methods and brings great clinical benefits.

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STUDY DESIGN: A multiple-comparative study between normal and low back pain (LBP) patients before and after rehabilitation. OBJECTIVE: To examine whether there is a change in flexion-relaxation phenomenon in sitting in LBP patient following a rehabilitation treatment. SUMMARY OF BACKGROUND DATA: There is an association between LBP and seated spine posture. Previous study has reported an absence of flexion-relaxation phenomenon in LBP patients during sitting. However, it is unknown whether there is a difference in flexion-relaxation phenomenon in sitting in LBP patients before and after rehabilitation treatment. METHODS: A total of 20 normal subjects and 25 chronic LBP patients who underwent a 12 weeks rehabilitation program were recruited. Surface electromyography recordings during upright sitting and flexed sitting were taken from the paraspinal muscles (L3) bilaterally from the normal subjects, and in the LBP patients before and after the rehabilitation treatment. The main outcome measures for patients include the visual analogue scale, Oswestry disability index, subjective tolerance for sitting, standing and walking, trunk muscle endurance, lifting capacity, and range of trunk motion in the sagittal plane. Flexion-relaxation phenomenon in sitting, expressed as a ratio between the average surface electromyography activity during upright and flexed sitting, was compared between normal and patients; and in LBP patients before and after rehabilitation. RESULTS: Flexion-relaxation ratio in sitting in normal subjects (Left: 6.83 +/- 3.79; Right: 3.45 +/- 2.2) presented a significantly higher (Left: P < 0.001; Right: P < 0.05) value than LBP patients (Left: 3.04 +/- 2.36; Right: 2.02 +/- 1.49). An increase in flexion-relaxation ratio in sitting was observed in LBP patients after rehabilitation (Left: 4.69 +/- 3.94, P < 0.05; Right: 3.58 +/- 2.97, P < 0.001), together with a significant improvement (P < 0.05) in subjective tolerance in sitting and standing, abdominal and back muscle endurance, lifting capacity, and range of motion. There were no significant changes in disability and pain scores, and subjective tolerance in walking. CONCLUSION: Flexion-relaxation ratio in sitting has demonstrated its ability to discriminate LBP patients from normal subjects, and to identify changes in pattern of muscular activity during postural control after rehabilitation.

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The objective of this study is to introduce dynamic topography of surface electromyography (SEMG) to visualize lumbar muscle myoelectric activity and provides a new view to analyze muscle activity in vivo. A total of 20 healthy male subjects and 15 males LBP were enrolled. An electrode-array was applied to the lumbar region to collect SEMG. The root mean square (RMS) value was calculated for each channel, and then a 160x120 matrix was constructed using a linear cubic spline interpolation of each scan to create a 2-D color topographic image. Along a definite interval of action, a series of RMS topography matrices was concatenated as a function of position and time, to form a dynamic topographical video of lumbar muscle activity. Relative area (RA), relative width (RW), relative height (RH) and Width-to-Height Ratio (W/H) were chosen as the four quantitative parameters in measuring topographic features. Normal RMS dynamic topography was found to have a consistent, symmetric pattern with a high intensity area in the paraspinal area. LBP patients had a different RMS dynamic topography, with an asymmetric, broad, or disorganized distribution. Quantitative SEMG features were found significantly different between normal control and LBP. After physiotherapy rehabilitation, the dynamic topography images of LBP tended towards the normal pattern. There are obvious differences in lumbar muscle coordination between healthy subjects and LBP patients. The dynamic topography allows the continuous visualization of the distribution of surface EMG signals and the coordination of muscular contractions.

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Brain-computer interfaces (BCIs) allow their users to communicate or control external devices using brain signals rather than the brain's normal output pathways of peripheral nerves and muscles. Motivated by the hope of restoring independence to severely disabled individuals and by interest in further extending human control of external systems, researchers from many fields are engaged in this challenging new work. BCI research and development have grown explosively over the past two decades. Efforts have recently begun to provide laboratory-validated BCI systems to severely disabled individuals for real-world applications. In this review, we discuss the current status and future prospects of BCI technology and its clinical applications. We will define BCI, review the BCI-relevant signals from the human brain, and describe the functional components of BCIs. We will also review current clinical applications of BCI technology, and identify potential users and potential applications. Finally, we will discuss current limitations of BCI technology, impediments to its widespread clinical use, and expectations for the future.

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The purpose of this study was to demonstrate the relative effect of electrocardiography (ECG) on back muscle surface electromyography (SEMG) parameters and their corresponding sensitivity in low back pain (LBP) assessment. Back muscle SEMG activities were recorded from 17 healthy subjects and 18 chronic LBP patients under static postures (straight sitting and upright standing), and dynamic action (flexion-extension). ECG cancellation based on independent component analysis (ICA) method was performed. Root mean square (RMS) and median frequency (MF) of raw and denoised SEMG data were computed respectively. Multiple comparisons were then performed. A consistent trend of change (increased MF and decreased RMS) followed ECG removal was noticed. In particular, in SEMG measurements under static postures, a significant decrease in RMS (p<0.05) and increase in MF (p<0.05) were found in all recording muscle groups. Level of corruption by ECG artifacts on SEMG measurements was found to be more serious and prominent in static postures than that in dynamic action. After ECG removal, significant improvements in the ability of SEMG to discriminate LBP patients from healthy subjects were seen in RMS amplitude recorded while standing (p<0.05) and MF in all measuring conditions (p<0.05). This study provides a more complete understanding on the relative effect of ECG contamination on back muscles SEMG parameters and LBP assessment.

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OBJECTIVE: To assess the health-related quality of life of patients with traumatic spinal cord injury living in Hong Kong. DESIGN: A cross-sectional retrospective study. SUBJECTS: Subjects with paraplegia following traumatic spinal cord injury were recruited from our department, which is one of the 3 main regional spinal cord injury rehabilitation centres in Hong Kong. A total of 120 potential participants were invited to join the study. The final study group comprised 58 patients (25 (43%) men and 33 (57%) women, 30 (50%) of whom were under 40 years of age). METHODS: Health-related quality of life was assessed using the Hong Kong Chinese version of the World Health Organization Quality of Life Measure Abbreviated version (WHO-QOL-BREF(HK)). Results were summarized and compared with previous results from healthy and other disease populations in Hong Kong. RESULTS: There was no significant difference in quality of life between men and women, or between different durations of spinal cord injury, different educational levels or different marital status (p > 0.05). However, a significant difference in quality of life was found in different age groups and between people with incomplete and complete paraplegia (p < 0.05). Compared with healthy and other disease populations, people with paraplegia had the lowest quality of life in Hong Kong (p < 0.001). CONCLUSION: People with paraplegia in Hong Kong have a lower quality of life than the general Hong Kong population. More community support is required to meet the needs of these patients in the areas of transportation, medical care and social life, in particular.

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