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

Toward A Zero Energy Home: Applying Swiss Building Practices/Attitudes to U.S. Residential Construction

This project evaluated typical U.S. and Swiss homes to identify construction practices that are most energy efficient and have economic payback. A net zero energy home (ZEH) produces as much energy as is consumed in it over time. Students in a College o f Technology in a Midwest Indiana State University and a technical University in Switzerland resulted in developing models of homes that combined U.S. and Swiss standards. The project was completed in two phases: during the first phase o f this project, construction costs, energy use, and economic payback was calculated for six homes that were designed using both Swiss and U.S. standards. During the second phase of the project, cultural norms that influence energy use were explored. A survey was used to compare U.S. and Swiss college students’ lifestyles and energy habits. All homes had the same basic size and layout, but some used construction practices typical for the United States and others were designed according to Swiss guidelines for residential construction. The results of the study showed that a Swiss-style low-energy home is not cost effective for the Midwestern United States if energy costs remain low, but it could become attractive if energy rates escalate significantly. It was also recognized that technology by itself will not minimize energy consumption, a result o f the second part o f the project that explored cultural norms that influence energy use. From the survey of both U.S. and Swiss college students’ lifestyles and energy habits, it was revealed with a high level of confidence that Swiss students are more energy conscious than their U.S. counterparts

Cerebral perfusion and sensory testing results differ in interstitial cystitis/bladder pain syndrome patients with and without fibromyalgia: A site-specific MAPP network study

Purpose: Fibromyalgia is a common co-morbidity in patients with interstitial cystitis/bladder pain syndrome. Quantitative sensory testing measures and regional cerebral blood flow measures have been noted to differ from healthy controls in both subjects with fibromyalgia and those with interstitial cystitis when studied independently. The present study examined such measures in subjects with the diagnosis of interstitial cystitis both with and without the co-diagnosis of fibromyalgia to determine whether differences in these measures may be associated with co-morbidity. Patients and Methods: Female subjects with the diagnosis of interstitial cystitis with (n = 15) and without (n = 19) the co-diagnosis of fibromyalgia as well as healthy control subjects (n = 41) underwent quantitative sensory testing. A subset of these patients (9 with and 9 without fibromyalgia) underwent brain perfusion studies using arterial spin labeled functional magnetic resonance imaging. An analysis was performed of absolute regional cerebral blood flow of regions-of-interest when experiencing a full bladder compared with an empty bladder. Results: Subjects with both interstitial cystitis and fibromyalgia were more hypersensitive than those without fibromyalgia as well as healthy controls in most sensory measures except heat. Subjects with interstitial cystitis, but no fibromyalgia, differed from healthy controls only in toleration of the ischemic forearm task. Other co-morbidities were more common in those subjects with both interstitial cystitis and fibromyalgia. Bladder fullness was associated with significantly greater whole brain gray matter blood flow in subjects with interstitial cystitis and fibromyalgia when compared with that of subjects with interstitial cystitis without fibromyalgia. Examination of regional cerebral blood flow in individual regions-of-interest demonstrated statistically significant differences between the subjects with interstitial cystitis with and those without fibromyalgia bilaterally in the thalamus, amygdala and hippocampus, as well as the right prefrontal cortex and greater responsiveness to changes in bladder fullness in the insula. Conclusion: Quantitative sensory testing and brain perfusion data support that there are two phenotypes of interstitial cystitis patients, which can be differentiated by a co-diagnosis of fibromyalgia. This may affect responsiveness to treatment and suggest the utility of stratifying interstitial cystitis patients according to their co-morbidities

Altered resting state neuromotor connectivity in men with chronic prostatitis/chronic pelvic pain syndrome: A MAPP: Research Network Neuroimaging Study.

Brain network activity associated with altered motor control in individuals with chronic pain is not well understood. Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS) is a debilitating condition in which previous studies have revealed altered resting pelvic floor muscle activity in men with CP/CPPS compared to healthy controls. We hypothesized that the brain networks controlling pelvic floor muscles would also show altered resting state function in men with CP/CPPS. Here we describe the results of the first test of this hypothesis focusing on the motor cortical regions, termed pelvic-motor, that can directly activate pelvic floor muscles. A group of men with CP/CPPS (N = 28), as well as group of age-matched healthy male controls (N = 27), had resting state functional magnetic resonance imaging scans as part of the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network study. Brain maps of the functional connectivity of pelvic-motor were compared between groups. A significant group difference was observed in the functional connectivity between pelvic-motor and the right posterior insula. The effect size of this group difference was among the largest effect sizes in functional connectivity between all pairs of 165 anatomically-defined subregions of the brain. Interestingly, many of the atlas region pairs with large effect sizes also involved other subregions of the insular cortices. We conclude that functional connectivity between motor cortex and the posterior insula may be among the most important markers of altered brain function in men with CP/CPPS, and may represent changes in the integration of viscerosensory and motor processing

Challenges and New Approaches to Proving the Existence of Muscle Synergies of Neural Origin

Muscle coordination studies repeatedly show low-dimensionality of muscle activations for a wide variety of motor tasks. The basis vectors of this low-dimensional subspace, termed muscle synergies, are hypothesized to reflect neurally-established functional muscle groupings that simplify body control. However, the muscle synergy hypothesis has been notoriously difficult to prove or falsify. We use cadaveric experiments and computational models to perform a crucial thought experiment and develop an alternative explanation of how muscle synergies could be observed without the nervous system having controlled muscles in groups. We first show that the biomechanics of the limb constrains musculotendon length changes to a low-dimensional subspace across all possible movement directions. We then show that a modest assumption—that each muscle is independently instructed to resist length change—leads to the result that electromyographic (EMG) synergies will arise without the need to conclude that they are a product of neural coupling among muscles. Finally, we show that there are dimensionality-reducing constraints in the isometric production of force in a variety of directions, but that these constraints are more easily controlled for, suggesting new experimental directions. These counter-examples to current thinking clearly show how experimenters could adequately control for the constraints described here when designing experiments to test for muscle synergies—but, to the best of our knowledge, this has not yet been done