Concurrent anticipation of two object dimensions during grasping in 10-month-old infants: A quantitative analysis

The anticipation of more than one object dimension while grasping for objects has been rarely investigated in infancy. The few existing studies by Newell et al. and Schum et al. have revealed mixed results probably mainly due to methodological limitations. Therefore, the present experiments tested concurrent anticipatory grasping for two object dimensions, namely, object size and object orientation using a quantitative motion capture system (Vicon), in 10-month-old infants and adults. We presented objects varying in size (small vs. large) and orientation (horizontally vs. vertically) and analyzed participants’ anticipatory hand configurations. As with adults, we observed that infants rotated their wrists, thumbs, and index fingers as a function of object orientation and adjusted their maximum grip apertures and their grip apertures shortly before they touched the objects as a function of object size. Analyses on an individual level showed that infants like adults anticipated both dimensions when the maximal values of aperture and angle were used but not when the measures shortly before touch were considered. Thus, the ability to anticipate more than one object dimension can already be observed at 10 months of age but seems to improve considerably over the first year of life.     

Acute effect of stretching modalities on global coordination and kicking accuracy in 12–13 year-old soccer players

The aim of the study was to compare the effect of stretching procedures on global coordination and accuracy in instep soccer kicks achieved in different stress conditions. Twenty male young soccer players completed the global coordination test (GC), the instep kicking accuracy test in free (FKA) and in time-pressure (TPKA) conditions, either after static (SS), dynamic (DS), ballistic (BS) or no-stretching (CTR) protocols, on nonconsecutive days and in a randomized order. After performing a 5 min standardized intensity jogging (70% of MAV), followed by stretching exercises for 10 min, each participant completed, successively, the GC, FKA and TPKA tests. Accuracy data, heart-rate, rating of perceived exertion and task difficulty perception were recorded and analyzed using a two-way ANOVA. GC scores were analyzed using one way ANOVA with repeated measures. The results showed higher GC and TPKA performances after DS and BS procedures. However, there was no effect of the stretching procedures on FKA. The GC scores increased by 10.8% and 7.2% after DS and BS, respectively, but were not affected by SS. Compared to FKA, the TPKA accuracy significantly decreased by 20.2% after CTR (p < 0.01) and 30.7% SS (p < 0.001) with no significant difference after DS (10.1%; p > 0.05) and BS (11.0%; p > 0.05). The use of dynamic and ballistic stretching yielded to better GC scores and helped reducing the adverse effect of time-pressure on instep kicking accuracy. Consequently, dynamic and ballistic exercises can be recommended before practicing activities requiring coordination and lower limbs speed and accuracy.     

The effect of variable rest intervals and chronic ankle instability on triplanar ankle motion during performance of the Star Excursion Balance Test

Inadequate rest intervals may contribute to impaired performance during functional tests. However, the effect of different rest intervals on performance of the SEBT in individuals with and without CAI is not known. Our purposes were to determine whether different rest intervals impact ankle kinematics during the SEBT and whether there differences between those two populations. 24 controls and 24 CAI completed 3 trials in 3 reach directions (anteromedial; AM, medial; M, posteromedial; PM). The order of rest intervals and reach distance were randomized and counterbalanced. Three visits were required to complete the 3 rest interval conditions (10, 20, 40 s). Rest interval did not impact ankle kinematics between controls and CAI during the SEBT. Dorsiflexion (DF) (AM:partial η² = 0.18; M:partial η² = 0.23; PM:partial η² = 0.23) for all directions and tibial internal rotation (TIR) excursions (AM:partial η² = 0.20) for AM direction were greater in individuals with CAI regardless of rest interval length. Rest intervals ranging from 10 to 40 s did not influence ankle kinematics. Differences exist in DF and TIR between controls and CAI during the SEBT. These findings suggest that clinicians can use any rest interval between 10 and 40 s when administrating the SEBT. However, triplanar motion differs during a complex functional movement in controls compared to CAI.     

经典力学革命中的概念图式变化

经典力学革命中起核心作用的是运动概念的变化。亚里士多德力学把运动理解成位移,这种运动概念与因果解释图式一起,限定了力学解释的基本特征。为了解决抛体问题而引入的冲力理论是一个过渡,伽利略在用冲力理论解释自由落体运动时改变了思考问题的方向,转向新的运动概念——运动就是瞬时运动。这个概念结合力学解释的因果图式预告了惯性定律。     

生物运动加工特异性：整体结构和局部运动的作用

人类具有很强的识别生物体运动信息的能力, 甚至当运动信息仅是由附着在头部和一些重要关节上的光点的运动组成时, 观察者对该信息检测和编码的优势依然存在。光点生物运动信息包含整体信息(如整体形状)和局部信息(如各个点的运动轨迹)。先前的绝大部分研究强调整体形状在生物运动知觉中的作用。最近有研究表明去除了整体结构信息的局部生物运动仍然存在加工优势, 揭示了局部生物运动本身可能包含了一些特异性信息。因此生物运动知觉并非单一现象, 而是一种具有不同加工机制(基于整体结构和基于局部运动)的多水平现象。     

客体运动方向的视觉工作记忆存储方式

采用变化觉察范式,以独立运动的客体为对象,通过两个实验,探讨多个客体的运动方向在视觉工作记忆中的存储机制,即单个对象独立存储,抑或其存储受多个客体构型的影响。实验一和实验二相继考察了非目标客体运动方向变化,以及是否存在非目标客体对觉察目标客体运动方向的影响。结果发现,非目标客体运动方向变化条件下的觉察正确率显著低于不变的条件,然而只呈现目标客体条件下的觉察正确率与同时呈现目标和非目标条件无显著差异。该结果与前人在静态条件下对目标客体的觉察受目标客体和非目标客体整体构型影响的结论不一致。本研究的结果支持多个客体的运动方向信息在工作记忆中是以独立方式存储的假设。     

基于时空变化的步态识别算法研究

本文提出了一种八椭圆人体模型,并在此基础上提出了基于变化信息的步态识别算法。对每个视频序列,采用基于贝叶斯规则的检测算法检测出目标人体区域;将目标人体区域按比例划分为八个区域并分别用椭圆拟合,建立人体椭圆模型;用人体姿势的时空变化——相邻帧间的模型参数的差值作为特征,用归一化后的Mahalanobis距离和Euclidean距离分别进行相似性度量,NN和KNN技术用于最终的分类。实验结果表明,该算法拥有较高的识别率和较低的计算代价。     

客体工作记忆研究的现状与展望

近年来, 大量的研究分别从行为和认知神经心理学的角度探讨了客体工作记忆的特性。行为水平上, 相关研究主要集中在客体工作记忆研究范式、客体在视觉工作记忆中的存储方式、视觉工作记忆容量等方面, 而客体工作记忆存储的争论体现在客体工作记忆存储的“强捆绑”假设、“特征-捆绑统一存储”假设、双重存储机制假设, 以及客体的捆绑等方面。认知神经水平上, 颞叶、枕叶和顶叶在视觉工作记忆中的作用不同, 顶叶、颞叶和前额叶在工作记忆特征捆绑和加工中起重要作用。     

老年人整体运动敏感性降低的脑灰质体积变化基础

本研究使用多体素模式分析方法和随机点阵范式,首次探索了老年人整体运动敏感性（GMS）下降和其脑灰质体积下降间的关系。结果发现,老年人GMS显著低于年轻人,老年人V5/MT、V3和额顶等脑区灰质体积显著小于年轻人;V5/MT和V3区的灰质体积信号可以有效预测个体的GMS。结果提示,V5/MT区和V3区,特别是V3区的灰质体积下降可能是老年人GMS下降的主要原因;而基于“去分化假设”,全脑范围内其余脑区的灰质体积下降可能也在一定程度上与老年人GMS下降有关。