Human neck reflex adaptation towards the frequency content of anterior-posterior torso perturbations

Introduction: Reflex modulation has been extensively reported during posture maintenance in response to task instructions, and to perturbation type, bandwidth and amplitude. For the head-neck system the modulation of the vestibulocollic (VCR) and cervicocollic (CCR) reflexes is essential to maintain upright head posture during unexpected disturbances. Previous studies have estimated that VCR and CCR contribute equally during perturbations in the sagittal plane; however, their modulation with respect to the properties of the disturbance remains unclear. This study seeks to establish how neck reflexes are modulated during perturbations with varying properties and how each reflex contributes to stabilization behavior. We hypothesized that VCR and CCR (a) modulate according to the perturbation bandwidth, (b) are unaffected by the perturbation amplitude and (c) increase when performing a visual acuity task. Methods: Twelve subjects were perturbed via the torso while restrained in a seated position on a motion platform. The anterior-posterior perturbations varied in bandwidth from 0.3 Hz to a maximum frequency of 1.2, 2.0, 4.0 and 8.0 Hz, at three different amplitudes, and with eyes open and closed. Results: Head kinematics and neck muscle EMG demonstrated significant (P < 0.05) changes due to bandwidth, which through modeling and closed loop identification were attributed to modulation of VCR and CCR gains. VCR and CCR demonstrated dominant contributions to stabilization during high (8.0 Hz) and low bandwidth (1.2 and 2.0 Hz) perturbations respectively, and equivalent contributions during mid bandwidth perturbations (4.0 Hz). However both were attenuated when perturbations exceeded the systems natural frequency (~2-3 Hz). Amplitude had an effect only for the lowest amplitude relative to other conditions attributed to thresholding properties of the semicircular canals. With eyes closed reflex gains decreased, attributed to the reduced ability to discriminate self-motion without vision. Conclusions: To maintain head-upright posture adaptations of neck reflexes are observed to occur due to perturbation frequency and visual task conditions but not amplitude. Estimation of reflex contributions demonstrates that previous literature has underestimated the contribution of CCR, particularly during low frequency perturbations

A Novel Approach for Modeling Neural Responses to Joint Perturbations Using the NARMAX Method and a Hierarchical Neural Network

The human nervous system is an ensemble of connected neuronal networks. Modeling and system identification of the human nervous system helps us understand how the brain processes sensory input and controls responses at the systems level. This study aims to propose an advanced approach based on a hierarchical neural network and non-linear system identification method to model neural activity in the nervous system in response to an external somatosensory input. The proposed approach incorporates basic concepts of Non-linear AutoRegressive Moving Average Model with eXogenous input (NARMAX) and neural network to acknowledge non-linear closed-loop neural interactions. Different from the commonly used polynomial NARMAX method, the proposed approach replaced the polynomial non-linear terms with a hierarchical neural network. The hierarchical neural network is built based on known neuroanatomical connections and corresponding transmission delays in neural pathways. The proposed method is applied to an experimental dataset, where cortical activities from ten young able-bodied individuals are extracted from electroencephalographic signals while applying mechanical perturbations to their wrist joint. The results yielded by the proposed method were compared with those obtained by the polynomial NARMAX and Volterra methods, evaluated by the variance accounted for (VAF). Both the proposed and polynomial NARMAX methods yielded much better modeling results than the Volterra model. Furthermore, the proposed method modeled cortical responded with a mean VAF of 69.35% for a three-step ahead prediction, which is significantly better than the VAF from a polynomial NARMAX model (mean VAF 47.09%). This study provides a novel approach for precise modeling of cortical responses to sensory input. The results indicate that the incorporation of knowledge of neuroanatomical connections in building a realistic model greatly improves the performance of system identification of the human nervous system

Association of the 6q23 region with the rate of joint destruction in rheumatoid arthritis

BACKGROUND: /st> Two novel genetic polymorphisms on chromosome 6q23 are associated with susceptibility to rheumatoid arthritis (RA). Both polymorphisms (rs6920220 and rs10499194) reside in a region close to the gene encoding tumour necrosis factor alpha-induced protein 3 (TNFAIP3). TNFAIP3 is a negative regulator of NF-kappaB and is involved in inhibiting TNF-receptor-mediated signalling effects. Interestingly, the initial associations were detected in patients with longstanding RA. However, no association was found for rs10499194 in a Swedish cohort with early arthritis. This might be caused by over-representation of patients with severe disease in cohorts with longstanding RA. OBJECTIVE: /st> To analyse the effect of the 6q23 region on the rate of joint destruction. METHODS: /st> Five single nucleotide polymorphisms in 6q23 were genotyped in 324 Dutch patients with early RA. Genotypes were correlated with progression of radiographic joint damage for a follow-up time of 5 years. RESULTS: /st> Two polymorphisms (rs675520 and rs9376293) were associated with severity of radiographic joint damage in patients positive for anti-citrullinated protein/peptide antibodies (ACPA). Importantly, the effects were present after correction for confounding factors such as secular trends in treatment. CONCLUSIONS: /st> These data associate the 6q23 region with the rate of joint destruction in ACPA+ RA.Pathophysiology and treatment of rheumatic disease

Рідке мило на основі соапстоків після нейтралізації олій та жирів в нейтралізуючому розчині, що містить етанол

Development and application of statistical models for medical scientific researc

Donor diabetes mellitus is a risk factor for diminished outcome after liver transplantation:a nationwide retrospective cohort study

BACKGROUND: With the growing incidence of diabetes mellitus (DM), an increasing number of organ donors with DM can be expected. We sought to investigate the association between donor DM with early post-transplant outcomes. METHODS: From a national cohort of adult liver transplant recipients (1996-2016), all recipients transplanted with a liver from a DM donor (n=69) were matched 1:2 with recipients of livers from non-DM donors (n=138). The primary end-point included early post-transplant outcome, such as the incidence of primary non-function (PNF), hepatic artery thrombosis (HAT), and 90-day graft survival. Cox regression analysis was used to analyze the impact of donor DM on graft failure. RESULTS: PNF was observed in 5.8% of grafts from DM donors versus 2.9% of non-DM donor grafts (p=0.31). Recipients of grafts derived from DM donors had a higher incidence of HAT (8.7% vs. 2.2%, p=0.03) and decreased 90-day graft survival (88.4% [70.9-91.1] vs. 96.4% [89.6-97.8], p=0.03) compared to recipients of grafts from non-DM donors. The adjusted hazard ratio for donor DM on graft survival was 2.21 (1.08-4.53, p=0.03). CONCLUSION: Donor DM is associated with diminished outcome early after liver transplantation. The increased incidence of HAT after transplantation of livers from DM donors requires further research

A conceptual exoskeleton shoulder design for the assistance of upper limb movement

© Springer International Publishing AG, part of Springer Nature 2018. There is an increased interest on wearable technologies for rehabilitation and human augmentation. Systems focusing on the upper limbs are attempting to replicate the musculoskeletal structures found in humans, reproducing existing behaviors and capabilities. The current work is expanding on existing systems with a novel design that ensures the maximum range of motion while at the same time allowing for lockable features ensuring higher manipulation payloads at minimum energy and fatigue costs. An analysis of the biomechanics of the shoulder is being done and a detailed system design for structural as well actuation elements of a parallel mechanism is given. The benefits for the use are discussed of reduced weight, maximum range of motion at minimum energy cost