Differential Effect of Two Mental Stress Tasks on Arterial Stiffness

Acute mental stress is believed to induce transient arterial dysfunction, but relatively few data are available. We therefore examined the effect of mental stress tasks that could induce differential hemodynamic responses on arterial dysfunction. Forty‐eight participants conducted either a mental arithmetic (MA) task or a mirror‐tracing (MT) task. Cardiovascular indices and arterial stiffness were measured before, during, and after these tasks. Analysis revealed that increases in arterial stiffness during the task and during recovery were more pronounced for the MA than for the MT, and that evoked hemodynamic response was more myocardial for MA than for MT. These results clearly show that MA and MT tasks that induce differential hemodynamic responses have a differential effect on arterial stiffness. This finding sheds light on the underlying mechanism that may account for the relationship between cardiovascular reactivity and cardiovascular disease.     

时间结构和速度线索对碰撞时间估计的影响

估计被遮挡的运动物体何时到达某一特定位置被称为碰撞时间估计,本研究利用遮挡范式,通过控制时间结构、物理速度及运动过程是否可见设计两个2（物理速度）×3（时间结构）实验来探究三者对碰撞时间估计的影响。结果：当时间结构一致时,不论物理速度快慢及是否存在视觉速度线索,被试的绩效都没有显著差异;当时间结构不一致时,不论物理速度快慢,存在视觉速度条件下被试的绝对偏差小于无视觉速度条件。结论：时间结构一致时,被试主要使用时间线索进行碰撞时间估计;时间结构不一致时,被试通过整合时间结构和视觉速度线索进行估计。     

Differential Method of Characterizing Gait Strategies From Step Lengths and Frequencies: Strategy of Velocity Modulation

The differential method consists of the analysis of the variation of gait parameters length, frequency, and velocity with respect to their mean values, respectively, ΔL = L — L_m , Δf = f — f_m , and Δv = v – v_m , where L_m , f_m , and v_m represent the mean values of those parameters. Assuming that the strategy of modulation of velocity implies that L and f are functions of v and that statistical analyses of ratios ΔL/Δv and Δf/Δv have established that there is a very significant linear correlation, close to 1, between those ratios, the mathematical procedure allows one to determine the equation of step length, L = a · f + b · v + K, where a and b are the slope and the intercept of the linear regression and K is close to L_m . The equation was experimentally tested on 140 gait sequences performed by 6 participants and for gait velocities ranging from 0.6 to 2.2 m/s and was found to be very representative of all individual values. The differential method provides another way of using the derivative of velocity, v = L·f, to characterize the strategy of velocity modulation, which then permits one to determine the linear equation of velocity, v = f · L_m + L · f_m — L_m · f_m , and to show that the respective parts played by each parameter in the progression velocity are approximately equal. The author establishes the uniqueness of the different linear adjustments and discusses the differential method's own modes of use, that is, interindividually or globally.     

Event-related cerebral hemodynamics reveal target-specific resource allocation for both “go” and “no-go” response-based vigilance tasks

Transcranial Doppler sonography was used to measure cerebral blood flow velocity (CBFV) in the right and left cerebral hemispheres during the performance of a 50-min visual vigilance session. Observers monitored a simulated flight of unmanned aerial vehicles for cases in which one of the vehicles was flying in an inappropriate direction relative to its cohorts. Two types of vigilance tasks were employed: a traditional task in which observers made button press (“go”) responses to critical signals, and a modification of the traditional task called the Sustained Attention to Response Task (SART) in which “go” responses acknowledged nonsignal events and response withholding (“no-go”) signified signal detection. Signal detections and global CBFV scores declined over time. In addition, fine-grained event-related analyses revealed that the detection of signals was accompanied by an elevation of CBFV that was not present with missed signals. As was the case with the global scores, the magnitude of the transient CBFV increments associated with signal detection also declined over time, and these findings were independent of task type. The results support the view of CBFV as an index of the cognitive evaluation of stimulus significance, and a resource model of vigilance in which the need for continuous attention produces a depletion of information-processing assets that are not replenished as the task progresses. Further, temporal declines in the magnitude of event-related CBFV in response to critical signals only is evidence that the decrement function in vigilance is due to attentional processing and not specific task elements such as the required response format.     

DETECTION OF THE VELOCITY OF MOVEMENT OF VISUAL STIMULI BY PIGEONS

Nine pigeons were trained to discriminate a moving stimulus from a stationary stimulus. In one experiment, the stimulus was a rotating disc with radial stripes. In a second experiment, the stimulus was a vertically moving film strip with horizontal bars. Several psychophysical procedures were used to determine the minimal detectable velocity of movement. The detection thresholds for most of the pigeons fell in the range of 4.4 to 6.5 millimeters per second, corresponding to a retinal velocity of 4.1 to 6.01 degrees per second. A signal detection analysis of the psychophysical data indicated systematic changes in response bias that were related to the ordinal position of the stimulus velocity in the sequence.     

学困儿童和学优儿童的手书特点比较

取小学生55名,其中25名为学困生,30名为学优生,使用数码写字板测试二者在横线自然手书状态下的速度、加速度、压力、波动和断续5个指标的变化特点。研究结果表明,学困生横线手书的速度超过学优生,特别是中间速度,差异显著。学困生的加速度增长比较快,在短期内维持在高速状态,然后快速下降,学优生增长速度比较慢,但是在很长的时间内保持在高速状态,最后加速度的递减明显比学困生慢,差异显著。学困生的加速度曲线形态趋势类似于一个倒U形,而学优生的曲线形态类似于梯形。学困生和学优生的压力变化呈现开始递增、然后保持在较高的压力状态的态势,但是二者之间没有显著差异。二者的波动都出现于书写的开始阶段,但是波动次数没有显著差异。在书写过程,二者都没有出现断续。     

Combined Effects of Movement Velocity and Duration on Programming Time: Spijkers (1989) Revisited

The goal of the present study was to determine the combined effects of movement velocity and duration on motor programming. Subjects were submitted to a two-choice reaction time task that could be completed by aiming movements differing in the mean velocity at which they were to be produced as well as by their movement time. The results of the present study indicate that, in each pair of responses used, the responses having the higher mean velocity were initiated faster than those having the lower mean velocity. Contrary to Spijkers' (1989) study, the different movement time pairings did not modify the effect of movement velocity on response programming time. Moreover, the same pattern of results was observed whether or not the subjects were permitted to visually guide their ongoing movement. Thus, Spijkers' proposition, that the type of control one may use to guide an aiming movement needs to be determined before movement initiation can take place, was not confirmed.     

Risk behaviour and mental workload: Multimodal assessment techniques applied to motorbike riding simulation

We present data from an ongoing research project on the cognitive, emotional and neuropsychological basis of risk behaviour. The main aim of the project is to build a model of risk behaviour so that if we know certain cognitive, behavioural and emotional variables, we will be able to predict decisions made in the face of uncertainty and risk, with the final goal of designing programs for evaluating, preventing and controlling risk behaviour. The objective of the present study was to look for individual differences in hazard perception during a static riding simulation and their relationship with mental workload. We used a multidimensional methodology, including behavioural, subjective and physiological data. The behavioural measures were obtained in a static riding simulation during eight hazard situations. We evaluated whether eye activity measures correlated with cognitive workload and different types of risky behaviours. Eye movement parameters were measured using a video-based eye tracking system. We found that risk-prone individuals showed specific patterns of risky behaviours and that peak of saccadic velocity and subjective mental workload indexes were both reliable indicators of risk proneness. Mental workload was higher for participants showing attitudes to risk behaviours probably because of a lack of conscious awareness of specific cues indicating dangerous scenarios.     

Breast Cancer and the Descent: The Loss and Return of Spring

This article approaches breast cancer as an initiation into a healing process that provides the opportunity for the transformation of a basic fault in the personality. Breast cancer will be approached as a metaphor alerting one to a crises of interiority, a loss of connection to ones inner dimension and ones feminine consciousness. This metaphor contains both the loss of the connection and the possibility of its recovery. The process involves a velocity of descent very difficult to endure; it involves a profound and accelerated unraveling of the rationality that previously served as a container stabilizing the ego. The perilousness of the descent imagery reflects the precipitousness of this unraveling. The precipitous descent is seen as an attempt of the soul to heal and reintegrate the personality by revisiting and illuminating a space abandoned long ago. The integration of this part of the personality results in a return of generativity, energy, and creativity.