Optimization of data pre-processing methods for time-series classification of electroencephalography data.

The performance of time-series classification of electroencephalographic data varies strongly across experimental paradigms and study participants. Reasons are task-dependent differences in neuronal processing and seemingly random variations between subjects, amongst others. The effect of data pre-processing techniques to ameliorate these challenges is relatively little studied. Here, the influence of spatial filter optimization methods and non-linear data transformation on time-series classification performance is analyzed by the example of high-frequency somatosensory evoked responses. This is a model paradigm for the analysis of high-frequency electroencephalography data at a very low signal-to-noise ratio, which emphasizes the differences of the explored methods. For the utilized data, it was found that the individual signal-to-noise ratio explained up to 74% of the performance differences between subjects. While data pre-processing was shown to increase average time-series classification performance, it could not fully compensate the signal-to-noise ratio differences between the subjects. This study proposes an algorithm to prototype and benchmark pre-processing pipelines for a paradigm and data set at hand. Extreme learning machines, Random Forest, and Logistic Regression can be used quickly to compare a set of potentially suitable pipelines. For subsequent classification, however, machine learning models were shown to provide better accuracy.

Trapezius activity during personal computer work with progressive addition lenses for general purpose and for computer work in neophytes.

INTRODUCTION: This study analysed the impact of general purpose progressive addition lenses (GP-PALs) and computer progressive addition lenses (PC-PALs) on the activity of the trapezius muscle during computer operation. METHODS: In this randomised, single-blinded, crossover study, surface electromyography (SEMG) signals were recorded bilaterally from the trapezius muscle during a 30-min computer task performed wearing different presbyopic corrections. The amplitude probability distribution function and its percentiles, gap frequency, muscular rest time and sustained low-level muscle activity periods were analysed in 32 subjects with artificially induced presbyopia. Subjectively perceived differences in vision and postural load between lenses were evaluated using a seven-item questionnaire (non-standardised, visual analogue scale ranged from 1 [bad] to 100 [good]). RESULTS: Considering the SEMG data, no significant difference in the muscular activity of the trapezius muscle was observed when using GP-PALs or PC-PALs for computer operation. However, PC-PALs showed statistically and clinically significantly higher results for subjectively perceived visual quality (78.4-31.3; p < 0.001), spontaneous tolerance (79.2-31.3; p < 0.001) and field of view (75.9-23.5; p < 0.001) compared with GP-PALs. CONCLUSIONS: Even though the electromyographic approach did not show a significant differentiation between the lenses, the subjective evaluation was clearly in favour of PC-PALs. Eye care practitioners should always take an occupational history of presbyopes, ask about the workplace situation and consider the use of PC-PALs.

Analysis of real-world visual ergonomics at the visual display unit.

INTRODUCTION: In this interventional study, the ergonomic workplace set-up and the impact of character size on subjectively estimated working productivity and computer vision syndrome (CVS) were evaluated in the field. METHODS: The number of displays and their size, resolution, surface structure, position in the room and relation to the eye were evaluated for 152 units. CVS was assessed using the CVS-Questionnaire. Habitually used character size for an uppercase E was recorded and compared to the ISO 9241-303:2011, national standards (e.g., ANSI/HFES 100-2007) and national guidelines (e.g., German DGUV Information 215-410). In case of failure to comply with these standards, character size was increased to 22 angular minutes to reach the recommended ranges. Reasons for returning to former or smaller character sizes were recorded, and subjectively perceived changes in productivity were estimated by the participants using a visual analogue scale before and 2 weeks after the intervention using a questionnaire. RESULTS: The average visual display unit consisted of two non-glare (matt) 24″ widescreen monitors that were located approximately 73 cm (primary) and 76 cm (secondary) from the eyes. The mean (SD) habitually set character size was 14.29 angular minutes (3.53) and therefore both statistically and clinically significantly too small compared with ISO 9241-303:2011 (p < 0.001). Increasing the character size to 22 angular minutes produced a 26% reduction in subjectively rated productivity (p < 0.001). No significant correlation between character size and symptoms of CVS was demonstrated. CONCLUSIONS: In the workplaces investigated, recommendations for character size were not adhered to. This resulted in a reduction in productivity and was not compatible with some of the work requirements, for example, obtaining a broad overview of a spreadsheet.

Surface Electromyography of the Trapezius and Sternocleidomastoid during Computer Work with Presbyopic Corrections.

SIGNIFICANCE: During computer work in controlled laboratory conditions, wearing multifocal contact lenses (MFCLs) showed no lower muscle load but increased subjective perception of comfort with equivalent visual quality and comparable tolerance. PURPOSE: Because musculoskeletal complaints are frequent among computer workers, this study used the muscle electrophysiological activity of shoulder and neck muscles in presbyopic computer workers who received either progressive addition lenses for general purpose (GP-PALs) or MFCLs. METHODS: For this crossover study, 11 presbyopic computer workers aged 55 ± 4 years (mean ± standard deviation) were equipped with GP-PALs and MFCLs in a randomized order. Surface electromyography signals were recorded bilaterally from shoulder and neck muscles during short-term computer work tasks using an optimally adjusted visual display unit workplace. The amplitude probability distribution function, the number and total duration of EMG gaps, and sustained low-level muscle activity periods of the surface electromyography signals were calculated. Comfort and correction type preferences were assessed. Head inclination was objectively evaluated. RESULTS: Multifocal contact lenses elicited no significant lower muscle load than GP-PALs. The number of sustained low-level muscle activity periods longer than 60 seconds was similar between visual aids. The total amount of gaps was significantly higher with MFCLs (44 gaps) compared with progressive addition lenses for general purpose (15 gaps) in all analyzed periods for all participants. However, there were no significant differences for the median in the intraindividual comparisons (P = .22, dz = 0.52). Multifocal contact lenses scored statistically significant higher in comfort values with equivalent visual quality and comparable tolerance (P = .003, dz = 1.51). CONCLUSIONS: Although the study failed to show clear results, wearing MFCLs seems to enhance working comfort compared with GP-PALs subjectively.

Comparison between Intramuscular Multichannel Electrodes and Supramysial Multichannel Electrodes via EMG Measurements for Potential Use as Larynx Stimulation Electrodes: In Vivo Animal Analysis.

One of the most common causes for larynx paralysis is the injury of the recurrent laryngeal nerve which, among others, causes the paralysis of the posterior cricoarytenoideus muscle (PCA). Electrical stimulation of PCA offers an approach to retaining the function of the paralyzed larynx muscle. The study aim was to test the applicability of an intramuscular multichannel array electrode as a measuring electrode for myoelectrical potentials and as a possible electrode for stimulation, e.g., posterior cricoarytenoideus muscle stimulation. For this purpose, two different kinds of electrodes were compared. 42 intramuscular multichannel array electrodes and 11 supramysial multichannel electrodes were implanted into the triceps brachii muscle of rats. The triceps brachii muscle of rats is suitable to serve as a substitute muscle for the human PCA muscle in an in vivo animal model. It has the same striated muscle cells, is of comparable size, and fundamentally serves a similar function to the human PCA muscle during normal respiration. Walking and breathing are circular functions that cause minimal muscle fatigue when carried out steadily. In total, the myoelectrical activity of 6703 steps could be recorded, allowing a comparison and statistical analysis of the EMG amplitudes and EMG activation patterns. Small differences can be detected between the EMG signals of both electrode types which, however, can be explained physiologically. Both electrode types reveal the basic characteristics of the triceps brachii muscle activity, namely the muscle contraction strength and the coordination pattern. This indicates that the intramuscular electrode may be applied for a detailed analysis of the human larynx.

Implications on older women of age- and sex-related differences in activation patterns of shoulder muscles: A cross-sectional study.

We conducted a cross-sectional study to assess differences in neuromotor attributes of shoulder muscles between age groups in both sexes and to better understand functional disorders in older women. Twenty young (20-42 years old), 20 middle-aged (43-67), and 20 older (> 68) adults participated in a comparative surface-electromyography study of five muscles. We identified age-related differences in women, especially in scapula stabilizer muscles. There was a tendency for both sexes of delayed onset times with increasing age, excepting the upper trapezius muscle in females. The results highlight the importance of understanding musculoskeletal aging in women to adequately guide physical therapeutic approaches.

Effects of wearing lower leg compression sleeves on locomotion economy.

The purpose of this investigation was to assess the effect of compression sleeves on muscle activation cost during locomotion. Twenty-two recreationally active men (age: 25 ± 3 years) ran on a treadmill at four different speeds (ordered sequence of 2.8, 3.3, 2.2, and 3.9 m/s). The tests were performed without (control situation, CON) and while wearing specially designed lower leg compression sleeves (SL). Myoelectric activity of five lower leg muscles (tibialis anterior, fibularis longus, lateral and medial head of gastrocnemius, and soleus) was captured using Surface EMG. To assess muscle activation cost, the cumulative muscle activity per distance travelled (CMAPD) of the CON and SL situations was determined. Repeated measures analyses of variance were performed separately for each muscle. The analyses revealed a reduced lower leg muscle activation cost with respect to test situation for SL for all muscles (p < 0.05, ηp2 > 0.18). The respective significant reductions of CMAPD values during SL ranged between 4% and 16% and were largest at 2.8 m/s. The findings presented point towards an improved muscle activation cost while wearing lower leg compression sleeves during locomotion that have potential to postpone muscle fatigue.

Interrelations of muscle functional MRI, diffusion-weighted MRI and (31) P-MRS in exercised lower back muscles.

Exercise-induced changes of transverse proton relaxation time (T2 ), tissue perfusion and metabolic turnover were investigated in the lower back muscles of volunteers by applying muscle functional MRI (mfMRI) and diffusion-weighted imaging (DWI) before and after as well as dynamic (31) P-MRS during the exercise. Inner (M. multifidus, MF) and outer lower back muscles (M. erector spinae, ES) were examined in 14 healthy young men performing a sustained isometric trunk-extension. Significant phosphocreatine (PCr) depletions ranging from 30% (ES) to 34% (MF) and Pi accumulations between 95% (left ES) and 120%-140% (MF muscles and right ES) were observed during the exercise, which were accompanied by significantly decreased pH values in all muscles (∆pH ≈ -0.05). Baseline T2 values were similar across all investigated muscles (approximately 27 ms at 3 T), but revealed right-left asymmetric increases (T2 ,inc ) after the exercise (right ES/MF: T2 ,inc = 11.8/9.7%; left ES/MF: T2 ,inc = 4.6/8.9%). Analyzed muscles also showed load-induced increases in molecular diffusion D (p = .007) and perfusion fraction f (p = .002). The latter parameter was significantly higher in the MF than in the ES muscles both at rest and post exercise. Changes in PCr (p = .03), diffusion (p < .01) and perfusion (p = .03) were strongly associated with T2,inc , and linear mixed model analysis revealed that changes in PCr and perfusion both affect T2,inc (p < .001). These findings support previous assumptions that T2 changes are not only an intra-cellular phenomenon resulting from metabolic stress but are also affected by increased perfusion in loaded muscles.

The musculoskeletal system of humans is not tuned to maximize the economy of locomotion.

Humans are known to have energetically optimal walking and running speeds at which the cost to travel a given distance is minimized. We hypothesized that "optimal" walking and running speeds would also exist at the level of individual locomotor muscles. Additionally, because humans are 60-70% more economical when they walk than when they run, we predicted that the different muscles would exhibit a greater degree of tuning to the energetically optimal speed during walking than during running. To test these hypotheses, we used electromyography to measure the activity of 13 muscles of the back and legs over a range of walking and running speeds in human subjects and calculated the cumulative activity required from each muscle to traverse a kilometer. We found that activity of each of these muscles was minimized at specific walking and running speeds but the different muscles were not tuned to a particular speed in either gait. Although humans are clearly highly specialized for terrestrial locomotion compared with other great apes, the results of this study indicate that our locomotor muscles are not tuned to specific walking or running speeds and, therefore, do not maximize the economy of locomotion. This pattern may have evolved in response to selection to broaden the range of sustainable running speeds, to improve performance in motor behaviors not related to endurance locomotion, or in response to selection for both.

Force capacity of back extensor muscles in healthy males: effects of age and recovery time.

To judge a person's maximum trunk extension performance as either age-appropriate or deconditioned is challenging. The current study aimed at determining age and anthropometrically adjusted maximum voluntary contraction (MVC) of back extensors considering the number and recovery time between trials. Thirty-one younger (20-30 years) and 33 older (50-60 years) healthy males performed five repetitions of maximal isometric trunk extensions in an upright standing position with randomized recovery times ranging between one to five minutes at one minute intervals. Torque values were normalized according to the individual's upper body mass resulting in upper body torque ratios (UBTR). To evaluate the impact of age, recovery time, and fatigue on UBTR we applied a linear mixed-effects model. Based on surface EMG data muscular fatigue could be excluded for both groups. For all MVC trials, UBTR levels differed significantly between age groups (range of mean values: younger: 2.26-2.28, older: 1.78-1.87, effect size: 1.00) but were independent from recovery time. However, the older males tended to exert higher UBTR values after shorter recovery periods. The study provides normative values of anthropometrically and age-group adjusted maximum back extensor forces. For the investigated groups, only two MVC trials with a recovery time of about one minute seem appropriate.

Comparison of sEMG Onset Detection Methods for Occupational Exoskeletons on Extensive Close-to-Application Data.

The design of human-machine interfaces of occupational exoskeletons is essential for their successful application, but at the same time demanding. In terms of information gain, biosensoric methods such as surface electromyography (sEMG) can help to achieve intuitive control of the device, for example by reduction of the inherent time latencies of a conventional, non-biosensoric, control scheme. To assess the reliability of sEMG onset detection under close to real-life circumstances, shoulder sEMG of 55 healthy test subjects was recorded during seated free arm lifting movements based on assembly tasks. Known algorithms for sEMG onset detection are reviewed and evaluated regarding application demands. A constant false alarm rate (CFAR) double-threshold detection algorithm was implemented and tested with different features. Feature selection was done by evaluation of signal-to-noise-ratio (SNR), onset sensitivity and precision, as well as timing error and deviation. Results of visual signal inspection by sEMG experts and kinematic signals were used as references. Overall, a CFAR algorithm with Teager-Kaiser-Energy-Operator (TKEO) as feature showed the best results with feature SNR = 14.48 dB, 91% sensitivity, 93% precision. In average, sEMG analysis hinted towards impending movements 215 ms before measurable kinematic changes.

EMG Amplitude-Force Relationship of Lumbar Back Muscles during Isometric Submaximal Tasks in Healthy Inactive, Endurance and Strength-Trained Subjects.

Previous data suggest a correlation between the cross-sectional area of Type II muscle fibers and the degree of non-linearity of the EMG amplitude-force relationship (AFR). In this study we investigated whether the AFR of back muscles could be altered systematically by using different training modalities. We investigated 38 healthy male subjects (aged 19-31 years) who regularly performed either strength or endurance training (ST and ET, n = 13 each) or were physically inactive (controls (C), n = 12). Graded submaximal forces on the back were applied by defined forward tilts in a full-body training device. Surface EMG was measured utilizing a monopolar 4 × 4 quadratic electrode scheme in the lower back area. The polynomial AFR slopes were determined. Between-group tests revealed significant differences for ET vs. ST and C vs. ST comparisons at the medial and caudal electrode positions, but not for ET vs. C. Further, systematic main effects of the "electrode position" could be proven for ET and C groups with decreasing x2 coefficients from cranial to caudal and lateral to medial. For ST, there was no systematic main effect of the "electrode position". The results point towards training-related changes to the fiber-type composition of muscles in the strength-trained participants, particularly for their paravertebral region.

Machine-Learning-Based Detecting of Eyelid Closure and Smiling Using Surface Electromyography of Auricular Muscles in Patients with Postparalytic Facial Synkinesis: A Feasibility Study.

Surface electromyography (EMG) allows reliable detection of muscle activity in all nine intrinsic and extrinsic ear muscles during facial muscle movements. The ear muscles are affected by synkinetic EMG activity in patients with postparalytic facial synkinesis (PFS). The aim of the present work was to establish a machine-learning-based algorithm to detect eyelid closure and smiling in patients with PFS by recording sEMG using surface electromyography of the auricular muscles. Sixteen patients (10 female, 6 male) with PFS were included. EMG acquisition of the anterior auricular muscle, superior auricular muscle, posterior auricular muscle, tragicus muscle, orbicularis oculi muscle, and orbicularis oris muscle was performed on both sides of the face during standardized eye closure and smiling tasks. Machine-learning EMG classification with a support vector machine allowed for the reliable detection of eye closure or smiling from the ear muscle recordings with clear distinction to other mimic expressions. These results show that the EMG of the auricular muscles in patients with PFS may contain enough information to detect facial expressions to trigger a future implant in a closed-loop system for electrostimulation to improve insufficient eye closure and smiling in patients with PFS.

High-resolution surface electromyographic activities of facial muscles during the six basic emotional expressions in healthy adults: a prospective observational study.

High-resolution facial surface electromyography (HR-sEMG) is suited to discriminate between different facial movements. Whether HR-sEMG also allows a discrimination among the six basic emotions of facial expression is unclear. 36 healthy participants (53% female, 18-67 years) were included for four sessions. Electromyograms were recorded from both sides of the face using a muscle-position oriented electrode application (Fridlund scheme) and by a landmark-oriented, muscle unrelated symmetrical electrode arrangement (Kuramoto scheme) simultaneously on the face. In each session, participants expressed the six basic emotions in response to standardized facial images expressing the corresponding emotions. This was repeated once on the same day. Both sessions were repeated two weeks later to assess repetition effects. HR-sEMG characteristics showed systematic regional distribution patterns of emotional muscle activation for both schemes with very low interindividual variability. Statistical discrimination between the different HR-sEMG patterns was good for both schemes for most but not all basic emotions (ranging from p > 0.05 to mostly p < 0.001) when using HR-sEMG of the entire face. When using information only from the lower face, the Kuramoto scheme allowed a more reliable discrimination of all six emotions (all p < 0.001). A landmark-oriented HR-sEMG recording allows specific discrimination of facial muscle activity patterns during basic emotional expressions.

Test-retest reliability of high-resolution surface electromyographic activities of facial muscles during facial expressions in healthy adults: A prospective observational study.

Objectives: Surface electromyography (sEMG) is a standard method for psycho-physiological research to evaluate emotional expressions or in a clinical setting to analyze facial muscle function. High-resolution sEMG shows the best results to discriminate between different facial expressions. Nevertheless, the test-retest reliability of high-resolution facial sEMG is not analyzed in detail yet, as good reliability is a necessary prerequisite for its repeated clinical application. Methods: Thirty-six healthy adult participants (53% female, 18-67 years) were included. Electromyograms were recorded from both sides of the face using an arrangement of electrodes oriented by the underlying topography of the facial muscles (Fridlund scheme) and simultaneously by a geometric and symmetrical arrangement on the face (Kuramoto scheme). In one session, participants performed three trials of a standard set of different facial expression tasks. On one day, two sessions were performed. The two sessions were repeated two weeks later. Intraclass correlation coefficient (ICC) and coefficient of variation statistics were used to analyze the intra-session, intra-day, and between-day reliability. Results: Fridlund scheme, mean ICCs per electrode position: Intra-session: excellent (0.935-0.994), intra-day: moderate to good (0.674-0.881), between-day: poor to moderate (0.095-0.730). Mean ICC's per facial expression: Intra-session: excellent (0.933-0.991), intra-day: good to moderate (0.674-0.903), between-day: poor to moderate (0.385-0.679). Kuramoto scheme, mean ICC's per electrode position: Intra-session: excellent (0.957-0.970), intra-day: good (0.751-0.908), between-day: moderate (0.643-0.742). Mean ICC's per facial expression: Intra-session: excellent (0.927-0.991), intra-day: good to excellent (0.762-0.973), between-day: poor to good (0.235-0.868). The intra-session reliability of both schemes were equal. Compared to the Fridlund scheme, the ICCs for intra-day and between-day reliability were always better for the Kuramoto scheme. Conclusion: For repeated facial sEMG measurements of facial expressions, we recommend the Kuramoto scheme.

Spatiotemporal characteristics of lower back muscle fatigue during a ten minutes endurance test at 50% upper body weight in healthy inactive, endurance, and strength trained subjects.

In modern developed societies, heavy physical demands are decreasing and getting replaced by longer periods of static, low-exertion activities such as sitting or standing. To counteract this lack of physical activity, more and more people are engaging in physical activity through exercise and training. Virtually opposite training modalities are endurance and strength. We asked if back muscle endurance capacity is influenced by training mode. 38 healthy male subjects (age range 19-31 years, mean age 22.6 years) were investigated: sedentary (Control, n = 12), endurance trained (ET, n = 13), and strength trained participants (ST, n = 13). They underwent a ten-minutes isometric extension task at 50% of their upper body weight. Surface EMG was measured in the low-back region utilizing quadratic 4*4 monopolar electrode montages per side. Relative amplitude and mean frequency changes were analysed with respect to electrode position and group during the endurance task. Eight ST subjects failed to complete the endurance task. Relative amplitude and frequency changes were largest in the ST group, followed by Control and ET groups (amplitude: F 6.389, p 0.004, frequency: F 11.741, p<0.001). Further, independent of group largest amplitude increase was observed for the most upper and laterally positioned electrodes. Mean frequency changes showed no systematic spatial distribution pattern. Although, in the light of an aging population, strength training has its merits our results question the functional suitability of frequent and isolated high-impact strength training for everyday endurance requirements like doing the dishes. Fatigue related amplitude elevations are systematically distributed in the back region, showing least fatigue signs for the most caudal and medial, i.e. the lumbar paravertebral region.

Wearable electroencephalography and multi-modal mental state classification: A systematic literature review.

BACKGROUND: Wearable multi-modal time-series classification applications outperform their best uni-modal counterparts and hold great promise. A modality that directly measures electrical correlates from the brain is electroencephalography. Due to varying noise sources, different key brain regions, key frequency bands, and signal characteristics like non-stationarity, techniques for data pre-processing and classification algorithms are task-dependent. METHOD: Here, a systematic literature review on mental state classification for wearable electroencephalography is presented. Four search terms in different combinations were used for an in-title search. The search was executed on the 29th of June 2022, across Google Scholar, PubMed, IEEEXplore, and ScienceDirect. 76 most relevant publications were set into context as the current state-of-the-art in mental state time-series classification. RESULTS: Pre-processing techniques, features, and time-series classification models were analyzed. Across publications, a window length of one second was mainly chosen for classification and spectral features were utilized the most. The achieved performance per time-series classification model is analyzed, finding linear discriminant analysis, decision trees, and k-nearest neighbors models outperform support-vector machines by a factor of up to 1.5. A historical analysis depicts future trends while under-reported aspects relevant to practical applications are discussed. CONCLUSIONS: Five main conclusions are given, covering utilization of available area for electrode placement on the head, most often or scarcely utilized features and time-series classification model architectures, baseline reporting practices, as well as explainability and interpretability of Deep Learning. The importance of a 'test battery' assessing the influence of data pre-processing and multi-modality on time-series classification performance is emphasized.

Electromyography of Extrinsic and Intrinsic Ear Muscles in Healthy Probands and Patients with Unilateral Postparalytic Facial Synkinesis.

There are currently no data on the electromyography (EMG) of all intrinsic and extrinsic ear muscles. The aim of this work was to develop a standardized protocol for a reliable surface EMG examination of all nine ear muscles in twelve healthy participants. The protocol was then applied in seven patients with unilateral postparalytic facial synkinesis. Based on anatomic preparations of all ear muscles on two cadavers, hot spots for the needle EMG of each individual muscle were defined. Needle and surface EMG were performed in one healthy participant; facial movements could be defined for the reliable activation of individual ear muscles' surface EMG. In healthy participants, most tasks led to the activation of several ear muscles without any side difference. The greatest EMG activity was seen when smiling. Ipsilateral and contralateral gaze were the only movements resulting in very distinct activation of the transversus auriculae and obliquus auriculae muscles. In patients with facial synkinesis, ear muscles' EMG activation was stronger on the postparalytic compared to the contralateral side for most tasks. Additionally, synkinetic activation was verifiable in the ear muscles. The surface EMG of all ear muscles is reliably feasible during distinct facial tasks, and ear muscle EMG enriches facial electrodiagnostics.

High-resolution surface electromyographic activities of facial muscles during mimic movements in healthy adults: A prospective observational study.

Objectives: Surface electromyography (sEMG) is a standard tool in clinical routine and clinical or psychosocial experiments also including speech research and orthodontics to measure the activity of selected facial muscles to objectify facial movements during specific facial exercises or experiments with emotional expressions. Such muscle-specific approaches neglect that facial muscles act more as an interconnected network than as single facial muscles for specific movements. What is missing is an optimal sEMG setting allowing a synchronous measurement of the activity of all facial muscles as a whole. Methods: A total of 36 healthy adult participants (53% women, 18-67 years) were included. Electromyograms were recorded from both sides of the face using an arrangement of electrodes oriented by the underlying topography of the facial muscles (Fridlund scheme) and simultaneously by a geometric and symmetrical arrangement on the face (Kuramoto scheme). The participants performed a standard set of different facial movement tasks. Linear mixed-effects models and adjustment for multiple comparisons were used to evaluate differences between the facial movement tasks, separately for both applied schemes. Data analysis utilized sEMG amplitudes and also their maximum-normalized values to account for amplitude differences between the different facial movements. Results: Surface electromyography activation characteristics showed systematic regional distribution patterns of facial muscle activation for both schemes with very low interindividual variability. The statistical significance to discriminate between the different sEMG patterns was good for both schemes (significant comparisons for sEMG amplitudes: 87.3%, both schemes, normalized values: 90.9%, Fridlund scheme, 94.5% Kuramoto scheme), but the Kuramoto scheme performed considerably superior. Conclusion: Facial movement tasks evoke specific patterns in the complex network of facial muscles rather than activating single muscles. A geometric and symmetrical sEMG recording from the entire face seems to allow more specific detection of facial muscle activity patterns during facial movement tasks. Such sEMG patterns should be explored in more clinical and psychological experiments in the future.

Single Application of Low-Dose, Hydroxyapatite-Bound BMP-2 or GDF-5 Induces Long-Term Bone Formation and Biomechanical Stabilization of a Bone Defect in a Senile Sheep Lumbar Osteopenia Model.

Effects of hydroxyapatite (HA) particles with bone morphogenetic BMP-2 or GDF-5 were compared in sheep lumbar osteopenia; in vitro release in phosphate-buffered saline (PBS) or sheep serum was assessed by ELISA. Lumbar (L) vertebral bone defects (Ø 3.5 mm) were generated in aged, osteopenic female sheep (n = 72; 9.00 ± 0.11 years; mean ± SEM). Treatment was: (a) HA particles (2.5 mg; L5); or (b) particles coated with BMP-2 (1 µg; 10 µg) or GDF-5 (5 µg; 50 µg; L4; all groups n = 6). Untouched vertebrae (L3) served as controls. Three and nine months post-therapy, bone formation was assessed by osteodensitometry, histomorphometry, and biomechanical testing. Cumulative 14-day BMP release was high in serum (76-100%), but max. 1.4% in PBS. In vivo induction of bone formation by HA particles with either growth factor was shown by: (i) significantly increased bone volume, trabecular and cortical thickness (overall increase HA + BMP vs. control close to the injection channel 71%, 110%, and 37%, respectively); (ii) partial significant effects for bone mineral density, bone formation, and compressive strength (increase 17%; 9 months; GDF-5). Treatment effects were not dose-dependent. Combined HA and BMPs (single low-dose) highly augment long-term bone formation and biomechanical stabilization in sheep lumbar osteopenia. Thus, carrier-bound BMP doses 20,000-fold to 1000-fold lower than previously applied appear suitable for spinal fusion/bone regeneration and improved treatment safety.