Postural adjustments and kinematic index finger features in frail older adults under different equilibrium constraints

Background: Anticipatory postural adjustments (APAs) are significantly affected by age and may represent restrictions on functional independence. Previous studies in young adults have already highlighted that changing postural stability (i.e., seated vs. upright posture) affects the motor planning and APAs. In frail older adults (FOAs), the effect of these different conditions of postural stability have not yet been established, and the present study aimed to disentangle this issue. Methods: Participants executed an arm-pointing task to reach a diode immediately after it turned on, under different conditions of stability (seated with and without foot support and in an upright posture). A kinematic profile of the index finger and postural electromyographic data were registered in their dominant-side leg muscles: Tibialis anterior, soleus, rectus femoris, and semitendinosus. Results: The main finding of this study was that the adopted posture and body stabilization in FOAs did not reflect differences in APAs or kinematic features. In addition, they did not present an optimal APA, since postural muscles are recruited simultaneously with the deltoid. Conclusion: Thus, FOAs seem to use a single non-optimal motor plan to assist with task performance and counterbalance perturbation forces in which they present similar APAs and do not modify their kinematics features under different equilibrium constraints

Análise comportamental e histológica de um modelo animal da doença de Parkinson em camundongos suíços

Parkinson’s disease (PD) is one of the most common aging-related neurodegenerative diseases, having a clinical presentation featuring classic motor symptoms related to the degeneration of dopaminergic neurons of the substantia nigra pars compacta (SNpc) and dopamine decr ease in the striatum. Animal models of PD are important tools employed by researcher aiming a better understading of pathophysiologic disease mechanisms and for evaluation of potential therapeutic interventions. Such models must mimic some aspect of the disease as for instances, the degeneration of nigral dopaminergic neurons. In this context, the PD model induced by the injection of the neurotoxina 6-hydroxydopamine (6-OHDA) has been widely established in rats but a better characterization in diferent mice strain is lacking, concerning both behavioral changes and the lesion in nigrostriatal system. Such characterization is important so that this model can be reliably used for investigations of therapeutic interventions. The goal of the present study was to improve the characterization of the unilateral 6-OHDA PD model using Swiss mice, through the evaluation of behavioral changes and the effects on the SNpc dopaminergic neurons. In this investigation we have used a single unilateral intraestriatal injection of 6-OHDA, in two different toxin concentrations: 10 µg/2µl e 20 µg/2 µl. Our results have demonstrated that both 6-OHDA concentrations used provoked severe loss of nigral dopaminergic neurons, amounting to 74,5% e 89,5% respectively. This neuronal loss was highly correlated to the apomorphine-induced rotational behavior but not to the ambulation assessed in the open field test. Therefore, intraestriatal injection of 10 µg/2µl or 20 µg/2µl of 6-OHDA, using Swiss mice, reproduce an effective unilateral 6-OHDA PD model that can be reliably employed in experiments aiming to investigate neuroprotective, cellular and/or pharmacological therapies for PD.A Doença de Parkinson (DP) é uma das doenças neurodegenerativas mais comuns relacionadas com a idade, e apresenta sintomatologia com alterações motoras clássicas que estão relacionadas com a degeneração dos neurônios dopaminérgicos da SNpc e a diminuição de dopamina no estriado. Modelos animais da DP são instrumentos importantes utilizados por pesquisadores para uma maior compreensão de mecanismos patológicos envolvidos na doença e para a avaliação de possíveis intervenções terapêuticas. Tais modelos devem mimetizar algum aspecto da doença, como a degeneração dos neurônios dopaminérgicos nigrais. Neste contexto, o modelo da DP induzido pela injeção da neurotoxina 6- hidroxidopamina (6-OHDA) já se encontra bem estabelecido em ratos, mas necessita ainda de melhor caracterização das alterações comportamentais e lesões no sistema nigro-estriatal em camundongos de diferentes linhagens a fim de que haja interpretações confiáveis quando o modelo for usado em testes terapêuticos. O presente estudo teve como objetivo melhorar a caracterização do modelo unilateral da DP com 6-OHDA em camundongos suíços, avaliando alterações comportamentais e o efeito sobre os neurônios dopaminérgicos da SNpc. Nesta investigação utilizou-se uma única injeção intraestriatal unilateral de 6-OHDA, em duas diferentes concentrações da toxina: 5µg/µl e 10µg/µl. Os nossos resultados mostraram que ambas as concentrações utilizadas causaram perda severa de neurônios dopaminérgicos na SNpc, com uma média de 74,5% e 89,5% de per da, respectivamente. Esta perda apresentou uma correlação alta com o comportamento rotatório induzido por apomorfina e uma correlação baixa com a ambulação no teste do campo aberto. Desta forma, injeções intraestriatais de 5µg/µl ou 10µg/µl de 6-OHDA, em camundongos suíços, reproduzem de forma efetiva o modelo animal unilateral da DP com 6-OHDA, podendo ser utilizadas de forma confiável em experimentos que visem a investigação de terapias farmacológicas, celulares e/ou de neuroproteção para a DP

Postural Adjustments in HTLV-1 Infected Patients during a Self-Initiated Perturbation

Background: Human T-cell lymphotropic virus type 1 (HTLV-1) infection can be associated with tropical spastic paraparesis (TSP/HAM), which causes neurological myelopathy and sensory and muscle tone alterations, leading to gait and balance impairments. Once trunk perturbation is predicted, the motor control system uses anticipatory and compensatory mechanisms to maintain balance by recruiting postural muscles and displacement of the body’s center of mass. Methods: Twenty-six participants (control or infected) had lower limb muscle onset and center of pressure (COP) displacements assessed prior to perturbation and throughout the entire movement. Results: Semitendinosus (ST) showed delayed onset in the infected group compared to the control group. The percentage of trials with detectable anticipatory postural adjustment was also lower in infected groups in the tibialis anterior and ST. In addition, COP displacement in the infected group was delayed, had a smaller amplitude, and took longer to reach the maximum displacement. Conclusions: HTLV-1 infected patients have less efficient anticipatory adjustments and greater difficulty recovering their postural control during the compensatory phase. Clinical assessment of this population should consider postural stability during rehabilitation programs

Comparison of inertial records during anticipatory postural adjustments obtained with devices of different masses

Background Step initiation involves anticipatory postural adjustments (APAs) that can be measured using inertial measurement units (IMUs) such as accelerometers. However, previous research has shown heterogeneity in terms of the population studied, sensors used, and methods employed. Validity against gold standard measurements was only found in some studies, and the weight of the sensors varied from 10 to 110 g. The weight of the device is a crucial factor to consider when assessing APAs, as APAs exhibit significantly lower magnitudes and are characterized by discrete oscillations in acceleration paths. Objective This study aims to validate the performance of a commercially available ultra-light sensor weighing only 5.6 g compared to a 168-g smartphone for measuring APAs during step initiation, using a video capture kinematics system as the gold standard. The hypothesis is that APA oscillation measurements obtained with the ultra-light sensor will exhibit greater similarity to those acquired using video capture than those obtained using a smartphone. Materials and Methods Twenty subjects were evaluated using a commercial lightweight MetaMotionC accelerometer, a smartphone and a system of cameras—kinematics with a reflective marker on lumbar vertebrae. The subjects initiated 10 trials of gait after a randomized command from the experimenter and APA variables were extracted: APAonset, APAamp, PEAKtime. A repeated measures ANOVA with post-hoc test analyzed the effect of device on APA measurements. Bland–Altman plots were used to evaluate agreement between MetaMotionC, smartphone, and kinematics measurements. Pearson’s correlation coefficients were used to assess device correlation. Percentage error was calculated for each inertial sensor against kinematics. A paired Student’s t-test compared th devices percentage error. Results The study found no significant difference in temporal variables APAonset and PEAKtime between MetaMotionC, smartphone, and kinematic instruments, but a significant difference for variable APAamp, with MetaMotionC yielding smaller measurements. The MetaMotionC had a near-perfect correlation with kinematic data in APAonset and APAamp, while the smartphone had a very large correlation in APAamp and a near-perfect correlation in APAonset and PEAKtime. Bland–Altman plots showed non-significant bias between smartphone and kinematics for all variables, while there was a significant bias between MetaMotionC and kinematics for APAamp. The percentage of relative error was not significantly different between the smartphone and MetaMotionC. Conclusions The temporal analysis can be assessed using ultralight sensors and smartphones, as MetaMotionC and smartphone-based measurements have been found to be valid compared to kinematics. However, caution should be exercised when using ultralight sensors for amplitude measurements, as additional research is necessary to determine their effectiveness in this regard

Wearable Inertial Sensor Approach for Postural Adjustment Assessments during Predictable Perturbations in Sport

Introduction: Evidence supports the importance of efficient postural control to improve performance in sports. This involves the use of strategies such as anticipatory posture adjustments and compensatory adjustments. Technology makes analysis and assessments in sports cheaper, while being valid and reliable compared to the gold-standard assessment equipment. Objectives: This article aimed to test the validity and reliability of signals extracted from the sensor’s accelerometer (Metamotion C), by comparing it to the data obtained from the gold-standard equipment (a three-dimensional video-motion-capture system). Design: Observational, cross-sectional study. Methods: We exposed 20 healthy young standing people to the pendulum impact paradigm, which consisted of predictable anteroposterior disturbances applied at the shoulder level. In order to measure this, we observed the acceleration of the center of mass in the anticipatory and compensatory phase of the disturbance and compared the signals of the two devices (Metamotion C and a motion-capture system). Results: The validation results showed the significant linear correlation of all variables with a moderate to large correlation of r ≥ 0.5 between the devices. In contrast, the reliability results between sessions obtained by filming were all significant and above 0.75, indicating excellent reliability. The APAonset variable had a reasonable to high intra-class correlation in the anticipatory phase. In the compensatory phase, the CPAtime variable showed an excellent correlation. Conclusions: Metamotion C proved reasonably valid and highly reliable in measuring the center of mass acceleration compared to the camera system in both the anticipatory and compensatory phases

Resumos concluídos - Neurociências

Resumos concluídos - Neurociência