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Purpose: Providing mobility solutions for individuals with tetraplegia remains challenging. Existing control devices have shortcomings such as varying or poor signal quality or interference with communication. To overcome these limitations, we present a novel myoelectric auricular control system (ACS) based on bilateral activation of the posterior auricular muscles (PAMs). Methods: Ten able-bodied subjects and two individuals with tetraplegia practiced PAM activation over 4 days using visual feedback and software-based training for 1 h/day. Initially, half of these subjects were not able to voluntarily activate their PAMs. This ability was tested with regard to 8 parameters such as contraction rate, lateralized activation, wheelchair speed and path length in a virtual obstacle course. In session 5, all subjects steered an electric wheelchair with the ACS. Results: Performance of all subjects in controlling their PAMs improved steadily over the training period. By day 5, all subjects successfully generated basic steering commands using the ACS in a powered wheelchair, and subjects with tetraplegia completed a complex real-world obstacle course. This study demonstrates that the ability to activate PAMon both sides together or unilaterally can be learned and used intuitively to steer a wheelchair. Conclusions:With the ACS we can exploit the untapped potential of the PAMs by assigning them a new, complex function. The inherent advantages of the ACS, such as not interfering with oral communication, robustness, stability over time and proportional and continuous signal generation, meet the specific needs of wheelchair users and render it a realistic alternative to currently available assistive technologies. [ABSTRACT FROM AUTHOR]

Transcranial direct current stimulation (tDCS) of the human motor cortex results in polarityspecific shifts of cortical excitability during and after stimulation. Anodal tDCS enhances and cathodal stimulation reduces excitability. Animal experiments have demonstrated that the effect of anodal tDCS is caused by neuronal depolarisation, while cathodal tDCS hyperpolarises cortical neurones. However, not much is known about the ion channels and receptors involved in these effects. Thus, the impact of the sodium channel blocker carbamazepine, the calcium channel blocker flunarizine and the NMDA receptor antagonist dextromethorphane on tDCS-elicited motor cortical excitability changes of healthy human subjects were tested, tDCS-protocols inducing excitability alterations (1) only during tDCS and (2) eliciting long-lasting after-effects were applied after drug administration. Carbamazepine selectively eliminated the excitability enhancement induced by anodal stimulation during and after tDCS. Flunarizine resulted in similar changes. Antagonising NMDA receptors did not alter current-generated excitability changes during a short stimulation, which elicits no after-effects, but prevented the induction of long-lasting after-effects independent of their direction. These results suggest that, like in other animals, cortical excitability shifts induced during tDCS in humans also depend on membrane polarisation, thus modulating the conductance of sodium and calcium channels. Moreover, they suggest that the after-effects may be NMDA receptor dependent. Since NMDA receptors are involved in neuroplastic changes, the results suggest a possible application of tDCS in the modulation or induction of these processes in a clinical setting. The selective elimination of tDCS-driven excitability enhancements by carbamazepine proposes a role for this drug in focussing the effects of cathodal tDCS, which may have important future clinical applications. [ABSTRACT FROM AUTHOR]

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Human-Machine Interfaces in rehabilitation engineering often use activity signals. Examples are electrical wheelchairs or prostheses controlled by means of muscle contractions. Activity signals are user-dependent and often reflect neurological weaknesses. Thus, not all users are able to operate the same control scheme in a robust manner. To avoid under- and overstraining, the interface ideally uses a control scheme which reflects the user’s control ability best. Therefore, we explored typical phenomena of activation signals. We derive criteria to quantify the user’s performance and abilities and present a routine which automatically selects and adapts one of three control schemes being best suited.

Abstract Physical exercise has been shown to increase neurogenesis, to decrease neuronal injury and to improve memory in animal models of stroke and head trauma. Therefore, we investigated the effect of voluntary wheel running on survival, neuronal damage and cell proliferation in a mouse model of pneumococcal meningitis. Mice were housed in cages equipped with voluntary running wheels or in standard cages before induction of bacterial meningitis by a subarachnoid injection of a Streptococcus pneumoniae type 3 strain. 24 hours later antibiotic treatment was initiated with ceftriaxone (100 mg/kg twice daily). Experiments were terminated either 30 hours or 4 days (short-term) or 7 weeks (long-term) after infection, and the survival time, inflammatory cytokines and corticosterone levels, neurogenesis in the dentate gyrus of the hippocampal formation and the cognitive function were evaluated in surviving mice. Survival time was significantly increased in running mice compared to control animals (p = 0.0087 in short-term and p = 0.016 in long-term experiments, log-rank test). At the end of the long-term experiment, mortality was lower in trained than in sedentary animals (p = 0.031, Fisher’s Exact test). Hippocampal neurogenesis – assessed by the density of doublecortin-, TUC-4- and BrdU + NeuN-colabeled cells - was significantly increased in running mice in comparison to the sedentary group after meningitis. However, Morris water maze performance of both groups 6 weeks after bacterial meningitis did not reveal differences in learning ability. In conclusion, physical exercise prior to infection increased survival in a mouse model of bacterial meningitis and stimulated neurogenesis in the dentate gyrus of the hippocampal formation.

Introduction Conflicting results have been reported on the importance of optimal TMS coil rotation. Maintaining a constant coil rotation angle manually remains a challenge. However, the exact impact of rotation angle on resting motor thresholds (RMTs) has not been investigated to date. Objective Using a robot-guided and a fully automated threshold hunting procedure, we aimed at determining the relevance of optimal rotation for determining RMT. Methods FDI hotspot was located with the automated hotspot hunting procedure ( n = 7). RMTs were then determined applying the threshold-hunting algorithm at different rotation angles (360° in steps of 15°, 15 pulses per rotation angle) in a randomized order over all pulses. The coil handle in posterior position was set as 0°. The procedure was repeated with steps of 5° within a 60° range of lowest thresholds of the first session. Threshold values were normalized for individual min and max. Results With 15° steps mean threshold was lowest at angles of 30° and 45°. Using 5° steps revealed a minimum mean threshold at 40° (mean threshold: 29.0; SEM: 0.05). A second minimum was found at the opposite angle. Highest RMTs were observed at angles between 135° and 180° and 285° and 315°. The relation between the rotation angle and deviation of the measured RMTs (from the minimum RMT at the optimal rotation angle) was non-linear with a floor effect between 5° and 15°. Conclusion Optimal coil rotation angle for FDI was found at 40°. Interestingly, within a range between 25° and 55° the effect of different coil rotation angles on the RMTs was not relevant, i.e. lower than the error of the threshold hunting procedure. The results therefore suggest that manual coil positioning at a rotation angle of 40° with little positional errors is uncritical when assessing motor thresholds of the FDI. [ABSTRACT FROM AUTHOR]

Introduction Strength and extension of the TMS-induced electromagnetic field increase with stimulation intensity at the expense of spatial accuracy.The concept of focality has not been investigated systematically in vivo yet. Objective To determine the focality of a given TMS coil we developed a linear mapping approach that assesses the correlation of intensity and spatial accuracy. Methods A line of 21 targets was placed in anterior–posterior direction through the center of gravity (COG) of the FDI hotspot with 2 mm spacing ( N = 8, Magstim 200 2 , 70 mm figure-8 coil).Recruitment curves were measured at each target with 15 pulses per intensity (threshold intensity + 1, 2 and 3% of maximum stimulator output (MSO)) with a randomized order over all targets and intensities.The probability was calculated as the ratio of pulses resulting in an MEP ⩾ 50 μV to the total number of pulses for each stimulation point and intensity.The intensities were categorized by the lowest intensity with a probability of 1 ( P 1) and lower ( P 1-1%, P 1-2% and P 1-3%).The bilateral data was centered on the COG, a logistic function ( P = A /(1+( x / x 0 ) p ) was fitted to the unilateral data to describe the relation of coil position, stimulation intensity and probability (MEP ⩾ 50 μV). The extent of FDI representation in relation to intensity was determined as two times the difference between the COG and the minimum of the 2nd derivative.Additionally, we calculated the slope width between the minimum and maximum of the 2nd derivative to determine the range at which the effective electric field leaves the hotspot, resulting in the highest decrease of probability.The extent of FDI and the slope width were plotted against the intensities to describe their correlation. Results A sigmoid relation between response rate and stimulation intensity was observed for all intensities.The plateau width (FDI extent) increased linear by 6.4 ± 1.3 mm/%MSO. In contrast, the slope width was 6.1 ± 0.2 mm across all intensities. Conclusion The results prove a linear relation of near threshold TMS intensities and focality with a decrease of spatial accuracy by 6.5 mm/%MSO when using a standard figure-8 coil.By calculating the slope widths of the intensity curves (6.1 mm) we propose a novel approach to determine the extent of a motor cortical representation that is not influenced by intensity. [ABSTRACT FROM AUTHOR]

Dystrophin deficiency in mice (mdx) is the most commonly used animal model for Duchenne muscular dystrophy (DMD). Compared to DMD patients, mdx mice show a milder phenotype. The objective of this study was to assess the temporal alteration of paraclinical and clinical parameters over 18 months with a focus on sensitive, objective and investigator independent measurement methods in mdx animals. 3-weeks old mdx mice and C57BL/10 controls (WT) were placed in separate cages equipped with a running wheel for 2 weeks every 3 months. Voluntary wheel running parameters were recorded continuously 24 h per day. Cardiac ultrasound was performed every 3 months. After 18 months, animals were sacrificed. Blood and muscle were sampled for ex vivo muscle contraction tests, quantitative PCR and histological analysis. All mdx ran with a ∼ 50 % lower daily distance, max. velocity (vmax) and run time in the first 9 months compared to WT mice (mdx, 5 km; WT, 10 km per day). WT mice kept a similar vmax from month 12 to 18 but the distance declined gradually over time. mdx mice displayed a tremendous reduction of the distance and vmax during the last 9 months of the experiment. Twitch force and specific maximal tetanic force were not diminished in M. soleus of mdx compared to WT at 18 months. The same parameters were drastically reduced in the mdx diaphragm (DIA). After 300 s of sustained repetitive stimulation, mdx DIA displayed no relevant fatigability. mRNA-expression and staining of fiber types revealed a predominance of type I and IIa fibers in mdx DIA at 18 months. Echocardiography data will be demonstrated. In conclusion, we demonstrate the first life-long, longitudinal voluntary wheel assessment in combination with cardiac ultrasound of mdx compared to Bl10 mice. We show morphological and functional changes of mdx muscles with the most striking difference being fatigue resistance of DIA. Our data should be helpful for the future planning of preclinical treatment trials for DMD. [ABSTRACT FROM AUTHOR]