A Common Force-Sharing Pattern in Joint Action That Consists of Four People

The authors examined the force-sharing patterns in a joint action performed by a group of two, three, or four people compared with a solo action. In the joint actions, 28 participants produced periodic isometric forces such that the sum of forces they produced cycled between 5% and 10% maximum voluntary contraction with the right hand at 1 Hz. In both the three- and four-person tasks, the correlation between forces produced by two of the three or four participants was negative, and the remaining one or two participants produced intermediate forces. The errors of force and interval and force variabilities were smaller in four- and three-people groups than individuals. Four- and three-people groups thus performed better than individuals.     

Effect of drugs on response-duration differentiation VII: response-force requirements

Rats were trained to press a lever for at least 1 s but for less than 1.3 s. The force required to press the lever was then increased or decreased by 10, 15, or 20 g. Increases in the force requirements for lever pressing decreased timing accuracy, but decreases in the force requirement had the opposite effect. Accuracy decreases at increasing force requirements were characterized by an increase in the relative frequency of responses that were too short to meet the reinforcement criterion. In contrast, increases in accuracy when the force requirements were decreased were characterized by increases in response durations that met the reinforcement criterion and decreases in the relative frequency of responses that were too short to produce the reinforcer. Phencyclidine (PCP) and methamphetamine produced dose-dependent decreases in accuracy that were associated primarily with increases in the relative frequency of short response durations, although methamphetamine also produced increases in long response durations at some doses. When the effects of PCP were determined with the force requirement increased by 10 g or decreased by 15 g, the cumulative response-duration distribution shifted toward even shorter response durations. When the effects of methamphetamine were determined with the force requirement on the lever increased by 10 g, the cumulative frequency distribution was shifted toward shorter response durations to about the same extent as it had been before force requirements increased; however, when the force required to press the lever was decreased by 15 g, these shifts toward shorter response durations almost completely disappeared. These results show that increases and decreases in the force requirements for lever pressing have different effects on the accuracy of temporal response differentiation.     

The influence of the human TMJ eminence inclination on predicted masticatory muscle forces

Aim of this paper was to investigate the change in masticatory muscle forces and temporomandibular joint (TMJ) reaction forces simulated by inverse dynamics when the steepness of the anterior fossa slope was varied. We used the model by de Zee et al. (2007) created in AnyBody™. The model was equipped with 24 musculotendon actuators. Mandibular movement was governed by the trajectory of the incisal point. The TMJ was modelled as a planar constraint canted 5° medially and the caudal inclination relative to the occlusal plane was varied from 10° to 70°. Our models showed that for the two simulated movements (empty chewing and unilateral clenching) the joint reaction forces were smallest for the eminence inclination of 30° and 40° and highest for 70°. The muscle forces were relatively insensitive to change of the eminence inclination for the angles between 20° and 50°. This did not hold for the pterygoid muscle, for which the muscle forces increased continually with increasing fossa inclination. For empty chewing the muscle force reached smaller values than for clenching. During clenching, the muscle forces changed by up to 200 N.     

The role of response force on the persistence and structure of behavior during extinction

Behavior Momentum Theory has emerged as a prominent account of resistance to change in both basic and applied research. Although laboratory studies often define precise, repeatable responses, application research often deals with response classes that may vary widely along a number of dimensions. In general, Behavior Momentum Theory has not addressed how response dimensions impact resistance to change, providing an opportunity to expand the model in new directions. Four rats pressed a force transducer under a multiple variable interval (VI) 60‐s VI 60‐s schedule of reinforcement. In one component, responses satisfied the schedule only if the response force fell within a “low” force band requirement; responses in the other schedule were required to satisfy a “high” force band. Once responding stabilized, extinction was programmed for three sessions. Then, the procedures were replicated. The results showed that response force came under discriminative control, but force requirements had no impact on resistance to extinction. In a follow‐up condition, the schedule was changed to a multiple VI 30‐s VI 120‐s schedule and the low‐force band operated in both components. The results showed that behavior maintained by the VI 30‐s schedule was generally more resistant to extinction. A secondary analysis showed that force distributions created under baseline maintained during extinction. Overall, the results suggest that differential response force requirements prevailing in steady state do not affect the course of extinction.     

规范伦理学之本体论质疑——海德格尔存在主义的视角

上世纪 6 0年代规范伦理学的复归是伦理学理论的一个发展 ,从存在主义的角度看 ,规范伦理学必然会碰到这样一些理论困境 :道德规范的根源如何确认 ?道德规范的确证是否可能 ?道德规范的约束力如何保证 ?道德规范如何适用于人之外的世界 ?     

A new approach to identifying the effect of diabetic peripheral neuropathy on the ability to drive safely

The purpose of this study was to estimate the potential for impaired driving performance in current drivers with diabetic peripheral neuropathy compared to healthy controls. We analysed, using a driving simulator, three important aspects of driving - use of the accelerator pedal, steering wheel and eye-steering coordination - to test for any differences, and then to integrate these findings to identify a unique pattern of changes in people driving with diabetic peripheral neuropathy. Patients with diabetic peripheral neuropathy displayed differences in use of the accelerator pedal compared to healthy control drivers (p < 0.05) which could be a direct consequence of their sensorimotor impairment due to diabetic peripheral neuropathy. Drivers with DPN used the more extreme high and low positions of the pedal to a greater extent than the Control group who exhibited a more graded use of the accelerator pedal over the mid-range. Eye-steering coordination was also different in drivers with diabetic peripheral neuropathy (p < 0.05) and, as it improved during the second drive, becoming closer to healthy drivers’ values, the occasional loss of control experienced during driving reduced. These insights demonstrate that diabetic peripheral neuropathy affects multiple aspects of driving performance suggesting the need for an integrated approach to evaluate the potential for driving safely in this population.     

Personality characteristics of fighter pilots and ground personnel

The training of fighter plane pilots is expensive, yet instruments are rarely used to screen potential pilots prior to flight training. Hence, a measure that can differentiate fighter pilots from other military personnel is needed. This study was an investigation of personality traits that are contributing factors for becoming a pilot in the Air Force, which could serve as screening tools. One hundred and twelve males were recruited from the Air Force university in Taiwan. Follow-up was conducted 2 years later with 73 students who became pilots and 39 who became ground personnel. A further 53 male military personnel of the same age served as controls. Structural equation modeling was used to show that pilots were more extraverted and less neurotic than the ground personnel, and more extraverted than the controls. Paternal overprotection had an indirect association with becoming a pilot through the mediation of the personality traits of extraversion and neuroticism. Mental health was not associated with becoming a pilot. The optimal cut-off point of 4/5 on a scale of extraversion resulted in a high sensitivity (96%) for differentiating between fighter pilots and controls. Independent of psychosocial stressors (mental health), extraversion is associated with the biological mechanisms of an individual, and plays a unique role in the process of becoming a pilot. Therefore, an extraversion index can be used for screening potential military pilots prior to flight training, as a means of reducing costs and managing human resources.     

Effects of antagonistic and synergistic muscles’ co-activation on mechanics of activated spastic semitendinosus in children with cerebral palsy

ObjectivesMost activities involve co-activation of several muscles and epimuscular myofascial force transmission (EMFT) can affect their mechanics. This can be relevant for spastic muscles of cerebral palsy (CP) patients. Isometric spastic semitendinosus (ST) forces vs. knee angle (KA-F_ST) data were collected intra-operatively to test the following hypotheses: (i) Inter-antagonistic EMFT elevates F_ST, (ii) changes the shape of KA-F_ST characteristics, (iii) reduces the muscle’s joint range of force exertion (Range-F_ST) and (iv) combined inter-antagonistic and synergistic EMFT further changes those effects.Methods11 limbs of 6 patients with CP (mean (SD) = 7.7 (4.7) years; GMFCS levels = II–IV) were tested in 3 conditions from 120° to full extension: ST activated (I) exclusively, (II) simultaneously with an antagonist, and (III) with added activation of synergists.ResultsCondition II increased F_ST (e.g., peak force = 87.6 N (30.5 N)) significantly (by 33.6%), but condition III caused no further change. No condition changed the muscle’s wide Range-F_ST (100.7° (15.9°)) significantly. Therefore, only the first hypothesis was confirmed.ConclusionsCo-activating its antagonist elevates forces of activated spastic ST substantially, but does not change its joint range of force exertion. Added activation of its synergists causes no further effects. Therefore, EMFT effects in CP can be relevant and need to be tested in other knee flexors.