H-reflex excitability is inhibited in soleus,but not gastrocnemius,at the short-latency response of a horizontal jump-landing task

Impaired spinal-level neuromuscular control is suggested to contribute to instability and injury during dynamic landing tasks. Despite this suggestion, spinal-level neuromuscular control is yet to be examined during a horizontal jump-landing task. The aim of the current study was to assess changes in H-reflexes and its reliability at the short-latency response of landings from short and long distances. Eight healthy individuals (five male, three female; age, 22 ± 1.2 yrs; height, 178 ± 8.1 cm; weight, 72 ± 15.7 kg) participated in the study. H-reflexes were evoked at the SLR in the soleus and medial gastrocnemius muscles, during two landing conditions: 25% and 50% of maximal broad jump distance. H-reflexes were expressed relative to the background electromyography (EMG) and maximal M-wave responses (M-max). Soleus H-reflexes were inhibited when landing from shorter distance (25%, 13.9 ± 7.6%; 50%, 8.3 ± 6.5%; p < 0.01). No change in H-reflex excitability was observed in medial gastrocnemius. Background EMG was unaltered across landing conditions. Inhibition of soleus H-reflex excitability from 25% to 50% landing condition indicates a reduced contribution of Ia-afferent feedback to the alpha-motor neuron during landings from greater distances, which may contribute to stiffness regulation at the ankle joint. Unaltered H-reflex excitability of medial gastrocnemius is most likely attributed to its functional role during the landing task.     

谈钱还是谈情:企业如何引导消费者分享自媒体营销

社交网络的发展弱化了传统媒体的影响力,强化了消费者的影响力;在这种情况下,企业需要思考如何借助消费者传播营销信息,以影响其他消费者。本文从企业如何设计营销信息入手,探究消费者与企业所处的关系范式对消费者信息转发行为的影响。通过二手数据分析与实验法,本文得出如下结论:经济类刺激对触发交易关系范式下消费者的转发行为更有效;情感类刺激对触发共有关系范式下消费者的转发行为更有效;交易关系范式下消费者出于回报企业的动机分享,共有关系范式下消费者出于利己动机而分享。     

The effects of sport dance on brain connectivity and body intelligence

Dancing is characterised by physical movement in accordance with rhythm perception. Twelve sport dancers and 12 age- and sex-matched young adults who had no dance experience (control group) were recruited. Body intelligence and brain activity were assessed in both groups using the Body Intelligence Scale (BIS) and resting state functional magnetic resonance imaging. BIS scores of dancers were higher than those of control subjects. The dancer group showed increased functional connectivity from the precentral gyrus to the right cingulate gyrus, right occipital fusiform gyrus, right inferior frontal gyrus, right medial frontal gyrus, left inferior frontal gyrus, right parietal postcentral gyrus, and right frontal lobe compared with control subjects. Sport dancers had increased body intelligence sensitivity compared with matched controls. In addition, the characteristics of dance, including physical movement in accordance with rhythm perception, might be associated with increased brain activity in the somatosensory and rhythm perception networks.     

Effects of translational background motion on visual localization

Three subjects were asked to judge the position of small spots of light flashed before, during or after rapid translational motion of the background grating pattern. Mislocalization of the spots was observed when the background moved during or immediately after presentation of the spot. In both cases, mislocalization always occurred in the direction of the fixation point. Furthermore, this mislocalization occurred only when the background moved in the opposite direction to the visual half-field in which the spot appeared. That is to say, a spot to the right of the fixation point was mislocalized when its background moved to the left, but not when it moved to the right, and the converse was also true. This finding was interpreted as reflecting a long-term adaptation to the optokinetic stimulation that we experience during forward and backward locomotion.     

A Time-Varying Measure of Dyadic Synchrony for Three-Dimensional Motion

We propose a novel approach to the analysis of synchronized three-dimensional motion in dyads. Motion recorded at high time resolution, as with a gaming device, is preprocessed in each of the three spatial dimensions by spline smoothing. Synchrony is then defined, at each time point, as the cosine between the two individuals’ estimated velocity vectors. The approach is extended to allow a time lag, allowing for the analysis of leader-follower dynamics. Mean square cosine over the time range is proposed as a scalar summary of dyadic synchrony, and this measure is found to be positively associated with cognitive empathy.     

第三方惩罚的神经机制：来自经颅直流电刺激的证据

第三方惩罚既是社会规范在群体得以维系的基石, 也是个体维护社会规范的体现。当前关注社会规范的神经研究大多基于第二方惩罚的独裁者或最后通牒实验框架, 缺乏对第三方维护社会规范过程中相关脑区活动的探索, 对这一过程的内在神经机制也不清楚。本文基于第三方惩罚的独裁者博弈框架, 对右侧背外侧前额叶区域(DLPFC)进行不同极性的经颅直流电刺激(tDCS), 同时依据第三方是否需要为其惩罚付出成本设计了零成本和有成本两个实验任务。结果发现, 第三方在零成本任务的情绪反应和惩罚显著受到tDCS设置的影响, 且阴极刺激显著提升了第三方的惩罚值, 这表明情绪机制对第三方惩罚有着重要影响。另外, 第三方在零成本和有成本任务中的惩罚差异在不同tDCS设置之间也存在显著差异, 这与第三方惩罚还受到自利机制影响的观点相符。本文率先为右侧DLPFC活动影响第三方惩罚提供了神经层面的证据, 且支持了第三方对社会规范的遵从与其负性情绪反应和自利加工密切相关的机制解释。     

Rhythmic priming across effector systems: A randomized controlled trial with Parkinson’s disease patients

This study investigated the immediate effects of auditory-motor entrainment across effector systems by examining whether Rhythmic Auditory Stimulation training of arm or finger movements would modulate gait speed. Forty-one participants with idiopathic Parkinson’s Disease were randomly assigned to 3 groups. Participants in the finger-tapping group tapped in synchrony with a metronome set to 20% faster pace than the pre-training walking cadence, whereas participants in the other group were asked to swing both arms in an alternating motion in synchrony with the metronome. Participants in the control condition did not receive training. To assess gait parameters pre- and post-training, participants walked on a 14-meter flat walkway at his/her preferred walking cadence with no auditory cueing. Results indicated that there was a significant increase in gait velocity after the finger tapping training (p < .005), whereas no differences were observed in the arm swing (p = .802) and in the control conditions (p = .525). Similarly, there were significant changes in gait cadence post-training in the finger tapping group (p < .005), but not after arm swing training (p = .879) or control (p = .759). There were no significant changes in stride length post-training in none of the groups. These findings suggest that auditory-motor entrainment in one effector system may prime a second effector system. Interestingly, however, the priming effect on gait was only observed in the finger tapping condition and not with synchronized arm swing movements. These findings have significant implications for motor rehabilitation and open new avenues for further investigation of the mechanisms underlying cross-effector coupling.     

Noninvasive brain stimulation over M1 and DLPFC cortex enhances the learning of bimanual isometric force control

Motor learning plays an important role in upper-limb function and the recovery of lost functionality. This study aimed to investigate the relative impact of transcranial direct current stimulation (tDCS) on learning in relation to the left primary motor cortex (M1) and left dorsolateral prefrontal cortex (DLPFC) during bimanual isometric force-control tasks performed with both hands under different task constraints. In a single-blind cross-over design, 20 right-handed participants were randomly assigned to either the M1 group (n = 10; mean age, 22.90 ± 1.66 years, mean ± standard deviation) or the DLPFC group (n = 10; mean age, 23.20 ± 1.54 years). Each participant received 30 min of tDCS (anodal or sham, applied randomly in two experiments) while performing the bimanual force control tasks. Anodal tDCS of the M1 improved the accuracy of maintenance and rhythmic alteration of force tasks, while anodal tDCS of the DLPFC improved only the maintenance of the force control tasks compared with sham tDCS. Hence, tDCS over the left M1 and DLPFC has a beneficial effect on the learning of bimanual force control.     

Testing the role of cognitive inhibition in physical endurance using high-definition transcranial direct current stimulation over the prefrontal cortex

The aim of this study was to clarify the role of the prefrontal cortex (PFC) in physical effort regulation. We hypothesized that the PFC would be progressively involved in physical endurance through the engagement of cognitive inhibition, which would be necessary to maintain effort by inhibiting fatigue-related cues. This hypothesis was examined using a double-blind, sham-controlled, within-subjects study (N = 20) using high-definition (HD) transcranial direct current stimulation (tDCS) over the right dorsolateral prefrontal cortex (dlPFC). Participants had to maintain a knee extensor contraction at 30% of their maximal force while simultaneously performing an Eriksen flanker task to evaluate their inhibition performance during the task. Anodal stimulation of the dlPFC influenced response to the cognitive task during exercise, as seen by slower response times and better accuracy. However, it did not lead to any measureable improvement in cognitive inhibition and did not influence endurance time. There was no correlation between cognitive inhibition and the maintenance of physical effort. This result does not indicate a relationship between cognitive inhibition and endurance performance. The contribution of the PFC in physical endurance could be explained through its involvement on decisional processes.