Signal in Human Motor Unsteadiness: Determining the Action and Activity of Muscles.

When the human skeleton is moved by muscles, the resulting movement is inherently unsteady. This work introduces two new approaches for using motor unsteadiness as a window into central nervous system function. The first approach, termed "Force Covariance Mapping" (FCM), demonstrates experimentally that there can be systematic differences in how forces exerted by limbs fluctuate depending on the direction of intended movement. Forces exerted in different directions by the human index finger were measured using a sensitive load cell. In certain directions of intended movement, forces were found to fluctuate in magnitude only, while in other directions of intended movement, forces were found to fluctuate in both direction and magnitude. Along with electromyographic (EMG) recordings and biomechanical estimates, force fluctuation data indicates that the central nervous system uses different muscular control strategies for different directions of intended movement: some movement directions are generated primarily by single muscles while others involve cooperation among multiple muscles. The second approach, termed "EMG-weighted averaging" (EWA), couples measures of electrical activity with concurrent motor unsteadiness to estimate the direction of mechanical contribution (action) for a muscle of interest. EWA tracks how exerted forces fluctuate after EMG in a particular muscle increases. This approach allows the exploration of complex neuromechanical phenomena "in vivo". EWA was applied to forces exerted isometrically by the human index finger and EMG data from two muscles: the first dorsal interosseous (FDI) and extensor indicis proprius (EIP) muscles. EWA estimates for the action direction of these muscles were found to change depending on the intended movement direction. These changes could relate to several hypotheses of muscle action, including differential control of motor units within a muscle as well as nonlinear summation of force among muscles. In addition, this work presents novel predictive equations describing spike-triggered averaging, a commonly-used neuroscience tool for understanding motor unit function that works by coupling motor unit electrical discharges with motor unsteadiness. Studying human motor unsteadiness, in the detail presented in this work, holds great promise for increasing our understanding human motor function and pathology.Ph.D.Applied and Interdisciplinary MathematicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/60825/1/jkutch_1.pd

Relationship between Surface and Indwelling EMG Spike Shape Measures

Indwelling electromyography (EMG) has great diagnostic value but its invasive and often painful characteristics make it inappropriate for monitoring human movement. Spike shape analysis of the surface electromyographic signal responds to the call for non-invasive EMG measures for monitoring human movement and detecting neuromuscular disorders. The present study analyzed the relationship between surface and indwelling EMG interference patterns. Twenty four males and twenty four females performed three isometric dorsiflexion contractions at five force levels from 20% to maximal force. The amplitude measures increased differently between electrode types, attributed to the electrode sensitivity. The frequency measures were different between traditional and spike shape measures due to different noise rejection criteria. These measures were also different between surface and indwelling EMG due to the low-pass tissue filtering effect. The spike shape measures, thought to collectively function as a means to differentiate between motor unit characteristics, changed independent of one another

The role of oscillatory synchrony in motor control.

Synchronized oscillations are manifest in various regions in the motor system. Their variable nature has increased the interest in the functional significance. Subcortical and cortical activity in the beta band is pathologically increased in Parkinson's disease (PD) - a state dominated by bradykinesia and rigidity. After the administration of the drug levodopa, beta activity and motor impairment are substantially decreased, while activity in the gamma band is increased. The function of beta bursts within the healthy motor system remains unknown. Recent evidence suggests that beta activity may promote the existing motor set and posture. In this thesis, with the use of positional hold tasks the role of beta activity on performance will be examined. It will be demonstrated that during bursts of beta synchrony in the corticomuscular system of healthy subjects there is an improvement, in the performance of these tasks. The findings will argue that physiological fluctuations in the beta band in the motor system may be of behavioural advantage during fine postural tasks involving the hand. The present work will also examine the role of population oscillations in the parkinsonian basal ganglia. It will demonstrate that under levodopa treatment the pattern of movement-related reactivity in the subthalamic nucleus (STN) and the pedunculopontine nucleus (PPN) as well as the background activity in the PPN change significantly. It will be shown that levodopa suppresses movement-related beta activity around the time of self-paced movements and promotes the increase of movement-related gamma activity contralateral to the movement side, following the same pattern as in the non dopamine-depleted brain. This suggests that dopaminergic therapy restores a more physiological pattern of reactivity in the STN. In the untreated state, beta activity in the STN will be shown to be modulated during repetitive self-paced movements, reflecting a role in ongoing performance, but only when motor performance is maximal and not when bradykinesia occurs. Finally, it will be demonstrated that levodopa promotes alpha band activity in the PPN at rest and before movement suggesting a possible physiological role of this activity in this nucleus. These observations provide further insight in the function of neuronal synchronization in the motor system in health and disease

Sensor Fusion in the Perception of Self-Motion

This dissertation has been written at the Max Planck Institute for Biological Cybernetics (Max-Planck-Institut für Biologische Kybernetik) in Tübingen in the department of Prof. Dr. Heinrich H. Bülthoff. The work has universitary support by Prof. Dr. Günther Palm (University of Ulm, Abteilung Neuroinformatik). Main evaluators are Prof. Dr. Günther Palm, Prof. Dr. Wolfgang Becker (University of Ulm, Sektion Neurophysiologie) and Prof. Dr. Heinrich Bülthoff.amp;lt;bramp;gt;amp;lt;bramp;gt; The goal of this thesis was to investigate the integration of different sensory modalities in the perception of self-motion, by using psychophysical methods. Experiments with healthy human participants were to be designed for and performed in the Motion Lab, which is equipped with a simulator platform and projection screen. Results from psychophysical experiments should be used to refine models of the multisensory integration process, with an mphasis on Bayesian (maximum likelihood) integration mechanisms.amp;lt;bramp;gt;amp;lt;bramp;gt; To put the psychophysical experiments into the larger framework of research on multisensory integration in the brain, results of neuroanatomical and neurophysiological experiments on multisensory integration are also reviewed

Haptics: Science, Technology, Applications

This open access book constitutes the proceedings of the 12th International Conference on Human Haptic Sensing and Touch Enabled Computer Applications, EuroHaptics 2020, held in Leiden, The Netherlands, in September 2020. The 60 papers presented in this volume were carefully reviewed and selected from 111 submissions. The were organized in topical sections on haptic science, haptic technology, and haptic applications. This year's focus is on accessibility

Swayed by sound: sonic guidance as a neurorehabilitation strategy in the cerebellar ataxias

Cerebellar disease leads to problems in controlling movement. The most common difficulties are dysmetria and instability when standing. Recent understanding of cerebellar function has expanded to include non -motor aspects such as emotional, cognitive and sensory processing. Deficits in the acquisition and processing of sensory information are one explanation for the movement problems observed in cerebellar ataxia. Sensory deficits result in an inability to make predictions about future events; a primary function of the cerebellum. A question therefore, is whether augmenting or replacing sensory information can improve motor performance in cerebellar disease. This question is tested in this thesis by augmenting sensory information through the provision of an auditory movement guide.A variable described in motor control theory (tau) was used to develop auditory guides that were continuous and dynamic. A reaching experiment using healthy individuals showed that the timing of peak velocity, audiomotor coordination accuracy, and velocity of approach, could be altered in line with the movement parameters embedded in the auditory guides. The thesis then investigated the use of these sonic guides in a clinical population with cerebellar disease. Performance on neurorehabilitation exercises for balance control was tested in twenty people with cerebellar atrophy, with and without auditory guides. Results suggested that continuous, predictive, dynamic auditory guidance is an effective way of improving iii movement smoothness in ataxia (as measured by jerk). In addition, generating and swaying with imaginary auditory guides was also found to increase movement smoothness in cerebellar disease.Following the tests of instantaneous effects, the thesis then investigated the longterm consequences on motor behaviour of following a two -month exercise with auditory guide programme. Seven people with cerebellar atrophy were assessed pre - and post -intervention using two measures, weight -shifting and walking. The results of the weight -shifting test indicated that the sonic -guide exercise programme does not initiate long -term changes in motor behaviour. Whilst there were minor, improvements in walking, because of the weight -shifting results, these could not be attributed to the sonic guides. This finding confirms the difficulties of motor rehabilitation in people with cerebellar disease.This thesis contributes original findings to the field of neurorehabilitation by first showing that on -going and predictive stimuli are an appropriate tool for improving motor behaviour. In addition, the thesis is the first of its kind to apply externally presented guides that convey continuous meaningful information within a clinical population. Finally, findings show that sensory augmentation using the auditory domain is an effective way of improving motor coordination in some forms of cerebellar disease

Space programs summary no. 37-62, volume 3 for the period 1 February - 31 March 1970. Supporting research and advanced development

Spacecraft communication, equipment, guidance, construction materials, propulsion, and related researc