Identification and Retraining of Sensorimotor Deficits to Reduce Intention Tremor in Multiple Sclerosis

Multiple sclerosis (MS) affects approximately 1 in 1000 Americans and is a significant cause of disability in the United States. One significant contributor to disability in MS is intention tremor, which manifests as an oscillation about the endpoint of a goal-directed movement. A major challenge of treating intention tremor is that the underlying causes of tremor in MS are unknown. In this study, we describe a systems-level computational model and an experimental technique that parameterizes subject-specific deficits in sensory feedback control during goal-directed movements. We used this approach to characterize sensorimotor control and examine how sensory and motor processes are differentially impacted by age and MS. The specific aims of this study were to: 1) characterize age-related changes in sensorimotor control during goal-directed movements; 2) characterize deficits in sensorimotor control in individuals with multiple sclerosis; and 3) determine whether sensorimotor control deficits can be modified and intention tremor reduced using robot-assisted therapy. We show that age-related changes in movement control can be ascribed to increases in sensory noise, leading to slower and less accurate movements. In persons with MS, changes in movement control associated with intention tremor can be attributed to increases in visual response delay that are unaccounted for by predictive neuromotor control mechanisms. Finally, we show that training of goal-directed movements using carefully selected feedback delays can enable subjects to adapt to their increased visual delay, thereby reducing system instability and tremor. The results demonstrate that systems identification techniques provide an informative framework for investigating how neuromotor disease affects motor control and for developing individually targeted rehabilitation strategies to reduce motor disability

Age-related differentiation of sensorimotor control strategies during pursuit and compensatory tracking

Motor control deficits during aging have been well-documented. Various causes of neuromotor decline, including both peripheral and central neurological deficits, have been hypothesized. Here, we use a model of closed-loop sensorimotor control to examine the functional causes of motor control deficits during aging. We recruited 14 subjects aged 19-61 years old to participate in a study in which they performed single-joint compensatory and pursuit tracking tasks with their dominant hand. We found that visual response delay and visual noise increased with age, while reliance on visual feedback, especially during compensatory tracking decreased. Increases in visual noise were also positively correlated with increases in movement error during a reach and hold task. The results suggest an increase in noise within the visuomotor control system may contribute to the decline in motor performance during early aging

Visual and Proprioceptive Contributions to Compensatory and Pursuit Tracking Movements in Humans

An ongoing debate in the field of motor control considers how the brain uses sensory information to guide the formation of motor commands to regulate movement accuracy. Recent research has shown that the brain may use visual and proprioceptive information differently for stabilization of limb posture (compensatory movements) and for controlling goal-directed limb trajectory (pursuit movements). Using a series of five experiments and linear systems identification techniques, we modeled and estimated the sensorimotor control parameters that characterize the human motor response to kinematic performance errors during continuous compensatory and pursuit tracking tasks. Our findings further support the idea that pursuit and compensatory movements of the limbs are differentially controlled

Intention Tremor and Deficits of Sensory Feedback Control in Multiple Sclerosis: a Pilot Study

Background Intention tremor and dysmetria are leading causes of upper extremity disability in Multiple Sclerosis (MS). The development of effective therapies to reduce tremor and dysmetria is hampered by insufficient understanding of how the distributed, multi-focal lesions associated with MS impact sensorimotor control in the brain. Here we describe a systems-level approach to characterizing sensorimotor control and use this approach to examine how sensory and motor processes are differentially impacted by MS. Methods Eight subjects with MS and eight age- and gender-matched healthy control subjects performed visually-guided flexion/extension tasks about the elbow to characterize a sensory feedback control model that includes three sensory feedback pathways (one for vision, another for proprioception and a third providing an internal prediction of the sensory consequences of action). The model allows us to characterize impairments in sensory feedback control that contributed to each MS subject’s tremor. Results Models derived from MS subject performance differed from those obtained for control subjects in two ways. First, subjects with MS exhibited markedly increased visual feedback delays, which were uncompensated by internal adaptive mechanisms; stabilization performance in individuals with the longest delays differed most from control subject performance. Second, subjects with MS exhibited misestimates of arm dynamics in a way that was correlated with tremor power. Subject-specific models accurately predicted kinematic performance in a reach and hold task for neurologically-intact control subjects while simulated performance of MS patients had shorter movement intervals and larger endpoint errors than actual subject responses. This difference between simulated and actual performance is consistent with a strategic compensatory trade-off of movement speed for endpoint accuracy. Conclusions Our results suggest that tremor and dysmetria may be caused by limitations in the brain’s ability to adapt sensory feedback mechanisms to compensate for increases in visual information processing time, as well as by errors in compensatory adaptations of internal estimates of arm dynamics

Determination of Variable Stiffness of a Human Elbow for Human-Robot Interaction

This paper aims to emulate human motion with a robot for the purpose of improving human-robot interaction (HRI). In order to engineer a robot that demonstrates functionally similar motion to humans, aspects of human motion such as variable stiffness must be captured. This paper successfully determined the variable stiffness humans use in the context of a 1 DOF disturbance rejection task by optimizing a time-varying stiffness parameter to experimental data in the context of a neuro-motor Simulink model. The significant improved agreement between the model and the experimental data in the disturbance rejection task after the addition of variable stiffness demonstrates how important variable stiffness is to creating a model of human motion. To enable a robot to emulate this motion, a predictive stiffness model was developed that attempts to reproduce the stiffness that a human would use in a given situation. The predictive stiffness model successfully decreases the error between the neuro-motor model and the experimental data when compared to the neuro-motor model with a constant stiffness value

Local Biomass Baselines and the Recovery Potential for Hawaiian Coral Reef Fish Communities

Understanding the influence of multiple ecosystem drivers, both natural and anthropogenic, and how they vary across space is critical to the spatial management of coral reef fisheries. In Hawaii, as elsewhere, there is uncertainty with regards to how areas should be selected for protection, and management efforts prioritized. One strategy is to prioritize efforts based on an area's biomass baseline, or natural capacity to support reef fish populations. Another strategy is to prioritize areas based on their recovery potential, or in other words, the potential increase in fish biomass from present-day state, should management be effective at restoring assemblages to something more like their baseline state. We used data from 717 fisheries-independent reef fish monitoring surveys from 2012 to 2015 around the main Hawaiian Islands as well as site-level data on benthic habitat, oceanographic conditions, and human population density, to develop a hierarchical, linear Bayesian model that explains spatial variation in: (1) herbivorous and (2) total reef fish biomass. We found that while human population density negatively affected fish assemblages at all surveyed areas, there was considerable variation in the natural capacity of different areas to support reef fish biomass. For example, some areas were predicted to have the capacity to support ten times as much herbivorous fish biomass as other areas. Overall, the model found human population density to have negatively impacted fish biomass throughout Hawaii, however the magnitude and uncertainty of these impacts varied locally. Results provide part of the basis for marine spatial planning and/or MPA-network design within Hawaii

In vitro comparison of performance including imposed work of breathing of CPAP systems used in low-resource settings.

Respiratory distress due to preterm birth is a significant cause of death in low-resource settings. The introduction of continuous positive airway pressure (CPAP) systems to treat respiratory distress significantly reduced mortality in high-resource settings, but CPAP was only recently introduced in low-resource settings due to cost and infrastructure limitations. We evaluated pressure stability and imposed work of breathing (iWOB) of five CPAP systems used in low resource settings: the Fisher and Paykel bubble CPAP, the Diamedica baby CPAP, the Medijet nCPAP generator, and the first (2015) and second (2017) generation commercially available Pumani CPAPs. Pressure changes due to fresh gas flow were evaluated for each system by examining the relationship between flow and pressure at the patient interface for four pressures generated at the bottle (0, 3, 5, and 7 cm H2O); for the Medijet nCPAP generator, no bottle was used. The slope of the resulting relationship was used to calculate system resistance. Poiseuille's law of resistance was used to investigate significant contributors to resistance. Resistance ranged from 0.05 to 1.40 [Formula: see text]; three CPAP devices had resistances 1.0 [Formula: see text]. Imposed WOB was measured using an ASL5000 test lung to simulate the breath cycle for an infant (5.5 kg), a term neonate (4.0 kg), and a preterm neonate (2.5 kg). Imposed WOB ranged from 1.4 to 39.5 mJ/breath across all systems and simulated infant sizes. Changes in pressure generated by fresh gas flow, resistance, and iWOB differ between the five systems evaluated under ideal laboratory conditions. The available literature does not indicate that these differences affect clinical outcomes

<i>Sophora microphylla</i> (Fabaceae) Microsatellite Markers and their Utility Across the Genus

Premise of the study: Genus-specific microsatellite markers were developed for Sophora for population genetic and systematic studies of the group in New Zealand, and potentially elsewhere in the geographic range. Methods and Results: From sequencing a total genomic DNA library (using Roche 454), we identified and developed 29 polymorphic microsatellite markers for S. microphylla and S. chathamica. We tested 12 of these markers on 14 S. chathamica individuals and four S. microphylla populations. All loci amplified in both species and species-specific alleles occurred at seven loci. In S. microphylla populations, the observed and expected heterozygosities ranged from 0.000–0.960 and 0.000–0.908, respectively, with alleles per locus ranging from seven to 23. Conclusions: The developed markers will be valuable in studies of phylogenetics, population structure, mating system, and selection of provenances for restoration projects

Medical Interventions for Chylothorax and their Impacts on Need for Surgical Intervention and admission characteristics: a multicenter, retrospective insight

The incidence of chylothorax is reported from 1-9% in pediatric patients undergoing congenital heart surgery. Effective evidenced-based practice is limited for the management of post-operative chylothorax in the pediatric cardiac intensive care unit. The study characterizes the population of pediatric patients with cardiac surgery and chylothorax who eventually require pleurodesis and/or thoracic duct ligation; it also establishes objective data on the impact of various medical interventions. Data were obtained from the Pediatric Health Information System database from 2004-2015. Inclusion criteria for admissions for this study were pediatric admissions, cardiac diagnosis, cardiac surgery, and chylothorax. These data were then divided into two groups: those that did and did not require surgical intervention for chylothorax. Other data points obtained included congenital heart malformation, age, gender, length of stay, billed charges, and inpatient mortality. A total of 3503 pediatric admissions with cardiac surgery and subsequent chylothorax were included. Of these, 236 (9.4%) required surgical intervention for the chylothorax. The following cardiac diagnoses, cardiac surgeries, and comorbidities were associated with increased odds of surgical intervention: d-transposition, arterial switch, mitral valvuloplasty, acute kidney injury, need for dialysis, cardiac arrest, and extracorporeal membrane oxygenation. Statistically significant medical interventions which did have an impact were specific steroids (hydrocortisone, dexamethasone, methylprednisolone) and specific diuretics (furosemide). These were significantly associated with decreased length of stay and costs. Dexamethasone, methylprednisolone, and furosemide were associated with decreased odds for surgical intervention. These analyses offer objective data regarding the effects of interventions for chylothorax in pediatric cardiac surgery admissions. Results from this study seem to indicate that most post-operative chylothoraxes should improve with furosemide, a low-fat diet, and steroids