排序方式: 共有81条查询结果,搜索用时 109 毫秒
61.
Frequency characteristics of head stabilization were examined during locomotor tasks in healthy young adults (N = 8) who performed normal walking and 3 walking tasks designed to produce perturbations primarily in the horizontal plane. In the 3 walking tasks, the arms moved in phase with leg movement, with abnormally large amplitude, and at twice the frequency of leg movement. Head-in-space angular velocity was examined at the predominant frequencies of trunk motion. Head movements in space occurred at low frequencies (< 4.0 Hz) in all conditions and at higher frequencies (> 4.0 Hz) when the arms moved at twice the frequency of the legs. Head stabilization strategies were determined from head-on-trunk with respect to trunk frequency profiles derived from angular velocity data. During natural walking at low frequencies (< 3.0 Hz), head-on-trunk movement was less than trunk movement. At frequencies 3.0 Hz or greater, equal and opposite compensatory movement ensured head stability. When arm swing was altered, compensatory movement guaranteed head stability at all frequencies. Head stabilization was successful for frequencies up to 10.0 Hz during locomotor tasks Maintaining head stability at high frequencies during voluntary tasks suggests that participants used feedforward mechanisms to coordinate head and trunk movements. Maintenance of head stability during dynamic tasks allows optimal conditions for vestibulo-ocular reflex function. 相似文献
62.
Given the flexible organization of locomotion evidenced in the many ways the limbs can be coordinated, the authors explored the potentially correspondingly flexible organization of nonvisual (kinesthetic) distance perception. As kinesthetic distance perception is known to be affected by how the limbs are coordinated, the authors probed the potential perceptual contribution of the arms during locomotion by manipulating arm–leg coordination patterns in blind-walked distance-matching tasks. Whereas manipulation of arm–leg coordination for walking with free-swinging arms had no observable perceptual consequences, comparable manipulation for walking with hiking poles did affect distance matching. These results suggest that under conditions in which the arms act to propel the body (e.g., crawling or stair-climbing) a person's nonvisual sense of movement is conveyed in the coordinated actions of all four limbs. 相似文献
63.
F. Pieruccini-Faria R. Vitório Q. J. Almeida C. R. A. Silveira M. J. D. Caetano F. Stella 《Journal of motor behavior》2013,45(5):369-380
The influence of dopaminergic replacement (DR) on gait in people with Parkinson's disease (PD) is well documented. However, little is known about the acute effects of dopamine on more complex locomotor tasks that require visual guidance to avoid obstacles during gait. The authors investigated the influence of DR on locomotor behavior in a task where movement planning and control might be challenged by the height of the obstacle. The PD group included patients diagnosed with idiopathic PD (n = 12), as well as healthy controls (n = 12). Patients walked and stepped over obstacles of different heights before (OFF) and after (ON) levodopa intake. Spatial adjustments were not modulated by DR, but the step time to perform these anticipatory gait adjustments was longer only in PD-OFF (compared with healthy controls) when approaching the highest obstacle, but not PD-ON. During the crossing phase, trail limb toe clearance of PD patients was shorter than healthy controls only during the OFF state. ON-OFF comparisons were significantly different only for the time to reach the lead foot clearance over the highest obstacle. In summary, DR partially improved movement slowness but did not directly affect movement amplitude of lower limb regulation in this gait task. 相似文献
64.
Treadmill locomotion can be characterized by consistent step-to-step kinematics despite the redundant degrees of freedom. The authors investigated the effect of disrupting the crural fascia in decerebrate cats to determine if the crural fascia contributed to kinematic variability and propulsion in the limb. Crural fasciotomy resulted in statistically significant decreases in velocity and acceleration in the joint angles during level walking, before, during, and after paw-off, particularly at the ankle. A further finding was an increase in variance of the limb segment trajectories in the frontal plane. The crural fascia therefore provides force transmission and reduction in kinematic variability to the limb during locomotion. 相似文献
65.
Francesca Sylos-Labini Yuri P. Ivanenko Germana Cappellini Alessandro Portone Michael J. MacLellan Francesco Lacquaniti 《Journal of motor behavior》2013,45(6):495-505
Gravity reduction affects the energetics and natural speed of walking and running. But, it is less clear how segmental coordination is altered. Various devices have been developed in the past to study locomotion in simulated reduced gravity. However, most of these devices unload only the body center of mass. The authors reduced the effective gravity acting on the stance or swing leg to 0.16g using different simulators. Locomotion under these conditions was associated with a reduction in the foot velocity and significant changes in angular motion. Moreover, when simulated reduced gravity directly affected the swing limb, it resulted in significantly slower swing and longer foot excursions, suggesting an important role of the swing phase dynamics in shaping locomotor patterns. 相似文献
66.
Caljouw SR van der Kamp J Lijster M Savelsbergh GJ 《Consciousness and cognition》2011,20(4):1135-1143
In the reported, experiment participants hit a ball to aim at the vertex of a Müller–Lyer configuration. This configuration either remained stable, changed its shaft length or the orientation of the tails during movement execution. A significant illusion bias was observed in all perturbation conditions, but not in the stationary condition. The illusion bias emerged for perturbations shortly after movement onset and for perturbations during execution, the latter of which allowed only a minimum of time for making adjustments (i.e., approx.170 ms). These findings indicate that allocentric information is exploited for online control when people make rapid adjustments in response to a sudden change in the environment and not when people guide their limb movements to interact with a stable environment. 相似文献
67.
In this study, 6-month-olds’ perception of an object-related human grasping action was compared with their level of grasping performance using a within-participants design. In the action perception task, infants were presented with the video of an actor’s grasping movement toward an occluded target object. Subsequently, an expected and an unexpected final state of this grasping movement were presented simultaneously, and infants’ looking times were measured. In the action production task, infants were presented with three graspable objects. Infants’ grasping behavior was coded to be either palmar or thumb-opposite grasping. Results indicate that infants who were already able to perform a thumb-opposite grasp differentiated between the two final states in the action perception task by looking longer toward the unexpected final state. In contrast, infants who showed only palmar grasps looked equally long toward both final states. This finding supports the assumption that action perception and action control are already closely related in infants as young as 6 months. 相似文献
68.
André M. Wong Mark De Santis Ph.D. 《Integrative psychological & behavioral science》1997,32(4):322-342
Sprague-Dawley rats were studied to learn whether gestation in the near-zero gravity, high radiation environment of space
impacts selected mammalian postnatal events. Ten rats spent days nine to twenty of pregnancy aboard the space shuttle orbiterAtlantis (STS-66). Their movement, was studied shortly after return to Earth; subsequently, several of their offspring were cross-fostered
and examined through postnatal day 81 (P81) for whole body growth and somatic motor development. Values for the flight animals
were compared to ground-based control groups. Relative to controls, the pregnant flight rats showed a marked paucity of locomotion
during the first few hours after returning to Earth. There was greater likelihood of perinatal morbidity for the offspring
of flight dams when compared to the control groups. Whole body weight of surviving offspring, averaged for each group separately,
showed typical sigmoidal growth curves when plotted against postnatal age. The flight group for our study had a larger ratio
of female to male pups, and that was sufficient to account for the lower average daily weight gained by the flight animals
when compared to the control groups. Walking was universally achieved by P13 and preceded eye opening which was complete in
all pups by P17. Thus, both of these developmental horizons were attained on schedule in the flight as well as the control
rats. Characteristic changes were observed in hind limb step length and gait width as the pups grew. These patterns occurred
at the same time in each group of rats. Therefore, prenatal space flight from days nine to twenty of gestation did not interfere
with the establishment of normal patterns for hind paw placement during walking. 相似文献
69.
The objectives of this study were: (a) to determine if the control mechanism for interacting with a dynamic real environment is the same as in the virtual reality (VR) studies, and (b) to identify the action control parameters that are modulated to successfully pass through oscillating doors. The participants walked along a 14-m path towards oscillating doors (rate of change in aperture size = 44 cm/s and maximum aperture varied 70, 80, or 100 cm). The participants had to use vision to extrapolate what the aperture of the doors would be at the time of crossing and determine if a change in action parameters was necessary. If their current state did not match the required state then the participants made modifications to their actions. The results showed that individuals in a real environment used similar action modifications (i.e., velocity adjustments) as those seen in VR studies to increase success. Aside from the gradual velocity adjustments observed, there was an immergence of a different locomotor action parameter on some trials that was not seen in VR studies (i.e., shoulder rotations). These shoulder rotations occurred when the participants perceived that a velocity adjustment alone would not lead to a successful trial. These results show that participants use perception to control movement in a feedback rather than feedforward manner. 相似文献
70.
Psychologists have long been captivated by the perception of animacy – the fact that even simple moving shapes may appear to engage in animate, intentional, and goal-directed movements. Here we report several new types of studies of a particularly salient form of perceived animacy: chasing, in which one shape (the ‘wolf’) pursues another shape (‘the sheep’). We first demonstrate two new cues to perceived chasing – chasing subtlety (the degree to which the wolf deviates from perfectly ‘heat-seeking’ pursuit) and directionality (whether and how the shapes ‘face’ each other). We then use these cues to show how it is possible to assess the objective accuracy of such percepts, and to distinguish the immediate perception of chasing from those more subtle (but nevertheless real) types of ‘stalking’ that cannot be readily perceived. We also report several methodological advances. Previous studies of the perception of animacy have faced two major challenges: (a) it is difficult to measure perceived animacy with quantitative precision; and (b) task demands make it difficult to distinguish perception from higher-level inferences about animacy. We show how these challenges can be met, at least in our case study of perceived chasing, via tasks based on dynamic visual search (the Find-the-Chase task) and a new type of interactive display (the Don’t-Get-Caught! task). 相似文献