Finger forces in fastball baseball pitching

Forces imparted by the fingers onto a baseball are the final, critical aspects for pitching, however these forces have not been quantified previously as no biomechanical technology was available. In this study, an instrumented baseball was developed for direct measurement of ball reaction force by individual fingers and used to provide fundamental information on the forces during a fastball pitch. A tri-axial force transducer with a cable having an easily-detachable connector were installed in an official baseball. Data were collected from 11 pitchers who placed the fingertip of their index, middle, ring, or thumb on the transducer, and threw four-seam fastballs to a target cage from a flat mound. For the index and middle fingers, resultant ball reaction force exhibited a bimodal pattern with initial and second peaks at 38–39 ms and 6–7 ms before ball release, and their amplitudes were around 97 N each. The ring finger and thumb produced single-peak forces of approximately 50 and 83 N, respectively. Shear forces for the index and middle fingers formed distinct peak at 4–5 ms before release, and the peaks summed to 102 N; a kinetic source for backspin on the ball. An additional experiment with submaximal pitching effort showed a linear relationship of peak forces with ball velocity. The peak ball reaction force for fastballs exceeded 80% of maximum finger strength measured, suggesting that strengthening of the distal muscles is important both for enhancing performance and for avoiding injuries.     

The representation of predictive force control and internal forward models: evidence from lesion studies and brain imaging

Force control on the basis of prediction avoids time delays from sensory feedback during motor performance. Thus, self-produced loads arising from gravitational and inertial forces during object manipulation can be compensated for by simultaneous anticipatory changes in grip force. It has been suggested that internal forward models predict the consequences of our movements, so that grip force can be programmed in anticipation of movement-induced loads. The cerebellum has been proposed as the anatomical correlate of such internal models. Here, we present behavioural data from patients with cerebellar damage and data from brain imaging in healthy subjects further elucidating the role of the cerebellum in predictive force control. Patients with cerebellar damage exhibited clear deficits in the coupling between grip force and load. A positron-emission-tomography (PET) paradigm that separated the process of the grip force/load coupling from the isolated production of similar grip forces and loads was developed. Interaction and conjunction analyses revealed a strong activation peak in the ipsilateral posterior cerebellum particularly devoted to the predictive coupling between grip force and load. Both approaches clearly demonstrate that the cerebellum plays a major role in force prediction that cannot be compensated for by other sensorimotor structures in case of cerebellar disease. However, evidence suggests that also extra-cerebellar structures may significantly contribute to predictive force control: (1) grip force/load coupling may also be impaired after cerebral and peripheral sensorimotor lesions, (2) a coupling-related activation outside the cerebellum was observed in our PET study, and (3) the scaling of the grip force level and the dynamic grip force coupling are dissociable aspects of grip force control.     

正误样例组合学习的相似性效应和认知加工深度效应

为了考察物体受力分析图正、误样例的相似程度以及被试对错误受力分析的认知加工(即对错误受力分析的辨别、解释和改正)水平对物体受力分析规则正误样例组合学习迁移效果的影响,以初中三年级学生为被试进行两项实验研究。实验结果表明:在物体受力分析图正误样例组合学习中存在明显的相似性效应,即正、误样例的相似程度越高,学习迁移的效果越好;对错误受力分析进行"改正"加工的学习迁移效果明显优于对错误的"辨别"加工,即存在明显的认知加工深度效应。     

准备状态对反应抑制的影响

从事件因素和时间因素两个方面探讨了准备状态对反应抑制的影响。事件准备可降低反应模式的不确定性 ,而时间准备则与降低反应时间的不确定性有关。线索、反应概率以及刺激呈现时间等因素不仅导致反应时间出现变化 ,还可引起反应力、心跳间期以及LRP和CNV等脑电指标发生变化。传统的反应抑制研究以反应时为指标 ,不能揭示反应抑制的内部过程 ,而心理生理学方法能弥补这一缺陷。生理指标与行为指标的结合 ,以及生理指标之间的结合 ,可更有效地探讨准备状态对反应抑制的效应。     

Independence of response force and reinforcement rate on concurrent variable-interval schedule performance

Five pigeons were trained over 43 experimental conditions on a variety of concurrent variable-interval schedules on which the forces required on the response keys were varied. The results were well described by the generalized matching law with log reinforcement ratios and log force ratios exerting independent (noninteractive) effects on preference. A further analysis using the Akaike criterion, an information-theoretic measure of the efficiency of a model, showed that overall reinforcement rate and overall force requirement did not affect preference. Unlike reinforcement rate changes, force requirement increases did not change the response rate on the alternate key, and an extension of Herrnstein's absolute response rate function for force variation on a single variable-interval schedule is suggested.     

21世纪的中西医结合

自本世纪６０年代以来,中西医结合取得了重要进展,中西医结合的经验与成果已经引起国内外重视。２１世纪,在“中西医并重”的方针指引下,将会迎来更好的发展机遇。兼客、互补与结合创新是主要的三种结合形式,其中结合创新占有更重要的地位。我们应增强创新意识,选好创新目标,改善临床与研究工作条件,为取得更快的发展而努力。     

The effects of response cost and response restriction on a multiple-response repertoire with humans

In two experiments a multiple-response repertoire of four free-operant responses was developed with university students as subjects using monetary gain as reinforcement. Following baseline, one of the responses was reduced either by making monetary loss contingent upon it (response cost) or by removing it from the repertoire (response restriction). In Experiment 1 a multielement baseline design was employed in which baseline and restriction or response-cost contingencies alternated semirandomly every 3 minutes. In Experiment 2 a reversal design was employed (i.e., baseline, restriction or response cost, then baseline), and each response required a different amount of effort. Both experiments had the following results: (a) The target response decreased substantially; (b) most nontarget responses increased, and the rest remained near their baseline levels; and (c) no support was found for Dunham's hierarchical, most frequent follower, or greatest temporal similarity rules. For several subjects, the least probable responses during baseline increased most, and the most probable responses increased least. Furthermore, in Experiment 2, responses with the lowest frequency of reinforcement increased most (for all 7 subjects), and those with the greatest frequency of reinforcement increased least (for 5 subjects).     

医德形成:外在强制与内在自觉

作为一种职业道德，医德的形成需要有一个过程。首先要以普通人或一般人的本质特性，即人是一个自由的有意识的存在者为前提条件。根据现代人的道德状况，将医德的形成分为两种路径，即医德形成的一般途径：靠制度约束的外在强制；医德形成的根本途径：对医生美德的内在自觉。     

Practicing Elements Versus Practicing Coordination: Changes in the Structure of Variance

ABSTRACT

The authors explored effects of practice of a 2-finger accurate force production task on components of finger force variance quantified within the uncontrolled manifold (UCM) hypothesis, V_UCM, that had no effect on total force and V_ORT that affected total force. A variable task with graded instability was designed to encourage use of variable solutions. Two groups of subjects (n = 9 each) were tested prior to a 1.5-hr practice session, after the session, and 2 weeks later (retention test). Group 1 practiced 1 finger at a time, while Group 2 practiced the task with 2 fingers (index and middle) pressing together. Both groups showed comparable improvements in the performance indices. Both groups showed a decrease in V_ORT, while only Group 2 showed an increase in V_UCM. These effects persisted during the retention test. The results show that practicing elements and practicing redundant groups of elements may lead to similar changes in performance (i.e., in the variability of the total force produced by the set of fingers), accompanied by dramatically different changes in the structure of variance: A drop in V_UCM after the single-finger practice and an increase following the 2-finger practice. The strong retention effects promise applications of the method to rehabilitation.     

基于驱动与控制相互作用的成瘾冲动性结构与机制

物质成瘾者具有明显的冲动性特征, 表现为难以戒断的成瘾物质使用。这种行为的产生除了抑制控制的问题外, 源于多个维度的驱动力也是重要的原因。低弱的抑制力无法抵挡驱力的作用, 出现不平衡状态, 形成难以控制的渴求下的强迫性用药或习惯性用药行为倾向。驱动力来源于多方面, 奖赏效应, 通过条件作用形成的S-R式相关线索反应以及感觉寻求等人格特质; 控制成分则包括了反应抑制与无法延迟满足的执行控制功能。