However, data did not reveal statistical significant differences in pointing performance between gravity levels. decrease in performance), and a statistically significant upward shifting in the vertical pointing direction during up-down inverted vision with respect to normal vision. Results show a statistically significant increase in reaction time and action time (i.e. error between the target position and the actual hit) were recorded using custom-built software. reaction time and duration of movement) and pointing accuracy (i.e. Seated subjects performed hand-pointing motions at randomly appearing dots on a 22-inch tactile display during 15 parabolas under three different gravity levels (0G, 1G, 1.8G) and two different visual conditions (normal, up-down inverted). Six subjects participated in a within-subject experiment during the 61st ESA and 112th CNES parabolic flight campaigns. Additionally, visual input can be altered using prisms that invert the visual scene. Parabolic flights provide a unique environment to understand the specific role of gravity since both vestibular and proprioceptive inputs, as well as the gravitational reference, are altered during the various gravity levels obtained. The integration of vestibular, visual, proprioceptive, and cognitive cues was investigated during a pointing task that required eye-hand coordination. The objective of this research effort was to assess the influence of gravity on these cognitive and sensorimotor processes. Here, we review research related to inherent capabilities and limitations of brain plasticity in terms of its spatial representations and discuss whether with appropriate training, humans can build perceptual and sensorimotor representations of spatial 4D environments, and how the presence or lack of ability of a solid and direct 4D representation can reveal underlying neural representations of space.Īn accurate perception of the body and the environment is important for programming pointing accuracy and controlling motor action. A fundamental question is whether our brains are inherently limited to 3D representations of the environment because we are living in a 3D world, or alternatively, our brains may have the inherent capability and plasticity of representing arbitrary dimensions however, 3D representations emerge from the fact that our development and learning take place in a 3D world. This adaptation continues in adulthood and is quite general to successfully deal with joint-space changes (longer arms due to growth), skull and eye size changes (and still being able of accurate eye movements), etc. Three-dimensional perceptual and sensorimotor capabilities emerge during development: the physiology of the growing baby changes hence necessitating an ongoing re-adaptation of the mapping between 3D sensory representations and the motor coordinates. These 3D representations underlie our 3D perceptions of the world and are mapped into our motor systems to generate accurate sensorimotor behaviors. ![]() By using multiple cues, such as disparity, motion parallax, perspective, our brains can construct 3D representations of the world from the 2D projections on our retinas. We live in a three-dimensional (3D) spatial world however, our retinas receive a pair of 2D projections of the 3D environment. The results show that updating of locations across saccades is not only fast, but is highly malleable, relying on recently learned sensorimotor contingencies. When on some trials the distractor was removed during the first saccade, saccades curved away only from the newly learned (but empty) location (Experiment 2). When on the minority of trials (20%) the targets were not shifted, saccades again first curved away from the newly learned (now empty) location, but then quickly switched to curving away from the life-long learned, visible location. After adaptation, second saccades curved away only from the newly learned distractor location starting at 80 ms after the first saccade. Critically, since the distractor was left stationary, successful saccade adaptation (e.g., saccade becoming shorter) meant that after the first saccade the distractor appeared in a different hemifield than without adaptation. During the first saccade both saccade targets were shifted on 80% of trials, which induced saccade adaptation (Experiment 1). ![]() The time-course of oculomotor updating was estimated using saccade curvature of the vertical saccade, relative to the distractor. Participants made a sequence of one horizontal and one vertical saccade and ignored an irrelevant distractor. Here we used saccade adaptation to alter life-long expectations about how a saccade changes the location of an object on the retina. Previous studies have shown that updating operates rapidly and starts before saccade is initiated. The oculomotor system uses a sophisticated updating mechanism to adjust for large retinal displacements which occur with every saccade.
0 Comments
Leave a Reply. |