Synergies and Motor Equivalence in Voluntary Sway Tasks: The Effects of Visual and Mechanical Constraints

The authors used two analyses developed within the framework of the uncontrolled manifold hypothesis to quantify multimuscle synergies during voluntary body sway: analysis of intertrial variance and analysis of motor equivalence with respect to the center of pressure (COP) trajectory. Participants performed voluntary sway tasks in the anteroposterior direction at 0.33 and 0.66 Hz. Muscle groups were identified in the space of muscle activations and used as elemental variables in the synergy analyses. Changing mechanical and vision feedback–based constraints led to significant changes in indices of sway performance such as COP deviations in the uninstructed, mediolateral direction and indices of spontaneous postural sway. In contrast, there were no significant effects on synergy indices. These findings show that the neural control of performance and of its stability may involve different control variables and neurophysiological structures. There were strong correlations between the indices of motor equivalence and those computed using the intercycle variance analysis. This result is potentially important for studies of patients with movement disorders who may be unable to perform multiple trials (cycles) at any given task, making analysis of motor equivalence of single trials a viable alternative to explore changes in stability of actions.     

班主任协商管理行为、师生关系与小学4~6年级学生外化问题行为的相互作用关系：交叉滞后研究

为探讨班主任协商管理行为、师生关系和学生外化问题行为三者间的相互作用关系, 在1个学年中, 采用问卷法对1407名小学4~6年级学生进行3次追踪测量。交叉滞后分析结果表明：(1)班主任协商管理行为启动积极的相互作用过程, T1时的班主任协商管理行为能显著减少T2时的学生的外化问题行为、提升T2时的师生关系亲密和降低T2时的师生关系冲突, 进而显著影响T3时的班主任协商管理行为、师生关系和学生外化问题行为; (2)学生外化问题行为驱动消极的相互作用过程, T1时的学生外化问题行为能显著减少T2时的班主任协商管理行为、降低T2时的师生关系亲密和增加T2时的师生关系冲突, 进而显著影响T3时的学生外化问题行为、师生关系和班主任协商管理行为。研究结果支持动态相互作用模型, 提示班主任在警醒学生外化问题行为的负面驱动作用的同时, 可有意识地利用协商管理行为的积极驱动作用干预学生的外化问题行为。     

Higher order balance control: Distinct effects between cognitive task and manual steadiness constraint on automatic postural responses

In the present experiment, we aimed to evaluate the interactive effect of performing a cognitive task simultaneously with a manual task requiring either high or low steadiness on APRs. Young volunteers performed the task of recovering upright balance following a mechanical perturbation provoked by unanticipatedly releasing a load pulling the participant’s body backwards. The postural task was performed while holding a cylinder steadily on a tray. One group performed that task under high (cylinder’ round side down) and another one under low (cylinder’ flat side down) manual steadiness constraint. Those tasks were evaluated in the conditions of performing concurrently a cognitive numeric subtraction task and under no cognitive task. Analysis showed that performance of the cognitive task led to increased body and tray displacement, associated with higher displacement at the hip and upper trunk, and lower magnitude of activation of the GM muscle in response to the perturbation. Conversely, high manual steadiness constraint led to reduced tray velocity in association with lower values of trunk displacement, and decreased rotation amplitude at the ankle and hip joints. We found no interactions between the effects of the cognitive and manual tasks on APRs, suggesting that they were processed in parallel in the generation of responses for balance recovery. Modulation of postural responses from the manual and cognitive tasks indicates participation of higher order neural structures in the generation of APRs, with postural responses being affected by multiple mental processes occurring in parallel.     

Mild Head Injury in Children and Adolescents

Although mild head injury is the most prevalent type of head injury in children and adolescents, only a relatively small number of studies on this kind of head injury have been reported. This article summarizes a review of studies examining cognitive, academic, and psychosocial outcomes in children who sustained mild head injuries. Despite earlier claims of mild head injury being a "silent epidemic," the studies, which were published from 1970 to 1998, provide no compelling evidence to support this view.     

First-order statistics of human stabilogram

We investigated the statistical properties of the centre of pressure (COP) vector during quiet standing, as measured on a force platform. To derive a statistical model for the data, the COP vector, locally averaged COP, and deviations from the average COP were analysed. Whereas indefinite multimodal distributions for the components of the COP were observed, the density functions of deviation from the averaged COP had reproducible properties. The anterior-posterior and mediolateral components of the deviations had in common that they were correlated variables with a non-circular statistic. The main axes of the equiprobability density curves were rotated with respect to the natural anterior-posterior and mediolateral directions. By means of more detailed statistical analysis of the data, two distinct populations of subjects were identified. In some cases we have found Gaussian distributions of the components of deviation from the average COP. In most cases the statistics was non-Gaussian. The average contrast, a new dimensionless characteristic quantity, independent of platform calibration, was introduced as a useful indicator of non-Gaussian effects in the postural control system.     

Driving skills after whiplash

Previous studies have shown that some persons with longlasting problems after whiplash have changed eye movements. These changes have been related to disturbance of the posture control system. The question raised in the present study is whether such disturbances can influence daily life functions connected with balance, position and external movements, such as car driving. A group of 23 persons with disturbed eye movements due to whiplash injury, was tested in a driving simulator, together with a closely matched control group. The results revealed significant differences between the two groups with respect to response times to the traffic signs presented, identification of type of sign, as well as steering precision while the subjects’ attention was directed to the process of identifying the signs. Alternative explanations such as driving experience, pain, medication or malingering are at least partly controlled for, but cannot completely be ruled out. A distorted posture control system leading to disturbance of eye movements seems to be the most likely primary causative factor, but these disturbances are most certainly complexly determined. Reduced attention capacity is considered to be a mediating secondary factor. Registration of eye movements may be a useful diagnostic tool to evaluate driving skill after whiplash.     

Reliability of forward head posture evaluation while sitting,standing, walking and running

Forward head posture has been evaluated mostly by visual observation or simple non-invasive measurements without a standardized evaluation method or protocol. In this experimental study, the reliability of existing forward head-posture measurement methods was evaluated by computing the intra-class correlation coefficients of three different head-position variables (two horizontal gap variables and one head-orientation variable) in seven different posture conditions from 20 asymptomatic participants. The position variables of the head were measured three times using a three-dimensional motion capture system while sitting comfortably, sitting with the back straight, standing comfortably, standing with the back straight, walking at 4 and 6 km/h on a treadmill, and running at 8 km/h on a treadmill. Intra-class correlation coefficients between repetitive measures ranged from 0.81 to 0.96, and high correlation coefficient values (>0.9) were produced when the head-position variables were measured during straight sitting, straight standing, and walking at 6 km/h. Among the three head-position variables, a horizontal gap between the tragus and the 7th cervical vertebra was recorded more consistently than other variables. Results of this study highlight the importance of a standardized evaluation protocol for more reliable assessment of the forward head posture.     

Embodied mood regulation: the impact of body posture on mood recovery,negative thoughts,and mood-congruent recall

Previous work has shown that a stooped posture may activate negative mood. Extending this work, the present experiments examine how stooped body posture influences recovery from pre-existing negative mood. In Experiment 1 (n?=?229), participants were randomly assigned to receive either a negative or neutral mood induction, after which participants were instructed to take either a stooped, straight, or control posture while writing down their thoughts. Stooped posture (compared to straight or control postures) led to less mood recovery in the negative mood condition, and more negative mood in the neutral mood condition. Furthermore, stooped posture led to more negative thoughts overall compared to straight or control postures. In Experiment 2 (n?=?122), all participants underwent a negative mood induction, after which half received cognitive reappraisal instructions and half received no instructions. Mood-congruent cognitions were assessed through autobiographical memory recall. Again, stooped (compared to straight) position led to less mood recovery. Notably, this was independent of regulation instruction. These findings demonstrate for the first time that posture plays an important role in recovering from negative mood.     

An improved energy efficient cluster head selection protocol using the double cluster heads and data fusion methods for IoT applications

The more energy consumption is the major issue for wireless sensor network. In wireless sensor network (WSN), sensor nodes are fixed in various routing algorithms. In the same networks, mobile sensor and fixed sensor nodes are combine and its used in few applications. The function is corruption while mobility was achieved, since these nodes have minimum battery power, lower range of communication and a lessor amount of memory. To overcome this issue, Improved Energy Efficient Cluster Head Selection protocol (IEECHS-WSN) is proposed, in these technique is used to transfer the received information by using energy efficient routing protocol. In the CH election method, two cluster heads are selected in a separated cluster and its work in various functions, this can be prolong the network lifetime and decrease the energy consumption of IoT applications. Proposed technique is described on clustering of dual CHs in the method of data fusion for data entropy. This information entropy is used for fusion and classification, the result of fusion and classification are accurate and efficient for data transmission. Our proposed IEECHS protocol has better throughput, lifetime of network and energy consumption compared than the existing technique.