Perception and control of low cable operation forces in voluntary closing body-powered upper-limb prostheses.

Operating a body-powered prosthesis can be painful and tiring due to high cable operation forces, illustrating that low cable operation forces are a desirable design property for body-powered prostheses. However, lower operation forces might negatively affect controllability and force perception, which is plausible but not known. This study aims to quantify the accuracy of cable force perception and control for body-powered prostheses in a low cable operation force range by utilizing isometric and dynamic force reproduction experiments.

Spatial resolution for EEG source reconstruction-A simulation study on SEPs.

Background: The accuracy of source reconstruction depends on the spatial configuration of the neural sources underlying encephalographic signals, the temporal distance of the source activity, the level and structure of noise in the recordings, and - of course - on the employed inverse method. This plenitude of factors renders a definition of 'spatial resolution' of the electro-encephalogram (EEG) a challenge.

New Method: A proper definition of spatial resolution requires a ground truth.

Cocontraction measured with short-range stiffness was higher in obstetric brachial plexus lesions patients compared to healthy subjects.

We suggest short range stiffness (SRS) at the elbow joint as an alternative diagnostic for EMG to assess cocontraction. Elbow SRS is compared between obstetric brachial plexus lesion (OBPL) patients and healthy subjects (cross-sectional study design). Seven controls (median 28years) and five patients (median 31years) isometrically flexed and extended the elbow at rest and three additional torques [2.

Fatigue-free operation of most body-powered prostheses not feasible for majority of users with trans-radial deficiency.

Background: Body-powered prostheses require cable operation forces between 33 and 131 N. The accepted upper limit for fatigue-free long-duration operation is 20% of a users' maximum cable operation force. However, no information is available on users' maximum force.

Quantifying Nonlinear Contributions to Cortical Responses Evoked by Continuous Wrist Manipulation.

Cortical responses to continuous stimuli as recorded using either magneto- or electroencephalography (EEG) have shown power at harmonics of the stimulated frequency, indicating nonlinear behavior. Even though the selection of analysis techniques depends on the linearity of the system under study, the importance of nonlinear contributions to cortical responses has not been formally addressed. The goal of this paper is to quantify the nonlinear contributions to the cortical response obtained from continuous sensory stimulation.

The effect of scaling physiological cross-sectional area on musculoskeletal model predictions.

Personalisation of model parameters is likely to improve biomechanical model predictions and could allow models to be used for subject- or patient-specific applications. This study evaluates the effect of personalising physiological cross-sectional areas (PCSA) in a large-scale musculoskeletal model of the upper extremity. Muscle volumes obtained from MRI were used to scale PCSAs of five subjects, for whom the maximum forces they could exert in six different directions on a handle held by the hand were also recorded.

Frequency response of vestibular reflexes in neck, back, and lower limb muscles.

Vestibular pathways form short-latency disynaptic connections with neck motoneurons, whereas they form longer-latency disynaptic and polysynaptic connections with lower limb motoneurons. We quantified frequency responses of vestibular reflexes in neck, back, and lower limb muscles to explain between-muscle differences. Two hypotheses were evaluated: 1) that muscle-specific motor-unit properties influence the bandwidth of vestibular reflexes; and 2) that frequency responses of vestibular reflexes differ between neck, back, and lower limb muscles because of neural filtering.

Parameter estimation of the Huxley cross-bridge muscle model in humans.

The Huxley model has the potential to provide more accurate muscle dynamics while affording a physiological interpretation at cross-bridge level. By perturbing the wrist at different velocities and initial force levels, reliable Huxley model parameters were estimated in humans in vivo using a Huxley muscle-tendon complex. We conclude that these estimates may be used to investigate and monitor changes in microscopic elements of muscle functioning from experiments at joint level.

Slowing of M1 activity in Parkinson's disease during rest and movement--an MEG study.

Objective: Parkinson's disease is characterized by motor and cognitive problems that are accompanied by slowing of neural activity. This study examined the relationship between neural slowing and disease severity during rest and motor performance.

Methods: Primary motor activity was assessed by means of magnetoencephalography during rest and rhythmic movements.

Differential after-effects of bimanual activity on mirror movements.

Using a rhythmic isometric force production paradigm, we investigated the after-effects of in-phase and antiphase bimanual performance on the unintended recruitment of the homologous muscles of the opposite limb during subsequent performance of tasks that were unimanual by design. Electromyograms obtained from the muscles of the opposite limb were analyzed in terms of their amplitude and the distribution of their phase relative to that of the intended movements. Preceding bimanual activity had distinct effects on the relative phase (mean and uniformity) of the structured electromyograms.