Avoiding moving obstacles
M. Pilar Aivar,M. Pilar Aivar,Eli Brenner,Eli Brenner,Jeroen B. J. Smeets,Jeroen B. J. Smeets +5 more
TL;DR: It is shown that quick responses of the hand to changes in obstacle position are possible, but that these responses are direct reactions to the motion in the surrounding, even when the possible change is predictable.
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Abstract: To successfully move our hand to a target, we must consider how to get there without hitting surrounding objects. In a dynamic environment this involves being able to respond quickly when our relationship with surrounding objects changes. People adjust their hand movements with a latency of about 120 ms when the visually perceived position of their hand or of the target suddenly changes. It is not known whether people can react as quickly when the position of an obstacle changes. Here we show that quick responses of the hand to changes in obstacle position are possible, but that these responses are direct reactions to the motion in the surrounding. True adjustments to the changed position of the obstacle appeared at much longer latencies (about 200 ms). This is even so when the possible change is predictable. Apparently, our brain uses certain information exceptionally quickly for guiding our movements, at the expense of not always responding adequately. For reaching a target that changes position, one must at some time move in the same direction as the target did. For avoiding obstacles that change position, moving in the same direction as the obstacle is not always an adequate response, not only because it may be easier to avoid the obstacle by moving the other way, but also because one wants to hit the target after passing the obstacle. Perhaps subjects nevertheless quickly respond in the direction of motion because this helps avoid collisions when pressed for time.
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Figures
Fig. 2 Results of experiment 1. Time is measured from the moment at which the target or obstacles could jump to a new position. Green no jump. Blue target jumps. Red obstacles jump. Continuous and dotted lines represent the two directions of the displacements. Central panel average signed velocity of the hand in the direction orthogonal to the main direction of motion. Arrows indicate our visual estimate of the latency of the response. Bottom panel number of subjects for whom the hand’s velocity was significantly different for the two directions of the displacement. Top panel percentage of trials in which the hand has reached the obstacle or target. The moment at which the hand had done so on 50% of the trials is also indicated by the thick vertical lines in the central panel 
Fig. 4 Results of experiment 3 . Time is measured from the moment at which the target or obstacles could jump to a new position. Green no jump. Blue target jumps. Red obstacles jump. Continuous lines and dotted lines represent the two kinds of displacements. Central panel average signed velocity of the hand in the direction orthogonal to the main direction of motion. Arrows indicate our visual estimate of the latency of the response. Bottom panel number of subjects for whom the hand’s velocity was significantly different for the two kinds of jump. Top panel percentage of trials in which the hand has reached the obstacle or target. The moment at which the hand had done so on 50% of the trials is also indicated by the thick vertical lines in the central panel 
Table 2 Individual results in experiment 2 
Fig. 1 Possible positions of the white target (shown here in blue) and of the red obstacle(s) in the three experiments. When either the target or obstacle(s) jumped the initial configuration (as in static trials) abruptly changed into one of the other four configurations (target jumps or obstacles jump). Blue and red arrows indicate the perceived direction of motion for the target and obstacle respectively, with continuous and dotted lines indicating the two directions of motion 
Fig. 3 Results of experiment 2. Time is measured from the moment at which the target or obstacle could jump to a new position. Green no jump. In this case there were two kinds of static trials because there were two different initial positions of the obstacle. Blue target jumps. Red obstacle jumps. Continuous and dotted lines represent the two directions of the displacements. Central panel average signed velocity of the hand in the direction orthogonal to the main direction of motion. Arrows indicate our visual estimate of the latency of the response. Bottom panel number of subjects for whom the hand’s velocity was significantly different for the two directions of the displacement (see main text for more details). For the obstacle, both responses in the direction of motion (light red) and those in the appropriate direction for avoiding the obstacle (dark red) are shown. Top panel percentage of trials in which the hand has reached the obstacle or target. The moment at which the hand had done so on 50% of the trials is also indicated by the thick vertical lines in the central panel 
Table 1 Individual results in experiment 1
Citations
A perspective on multisensory integration and rapid perturbation responses
TL;DR: The limitation of current models of multisensory integration in light of these asynchronous processing delays is discussed, and it is suggested that understanding how the brain performs real-time multisENSory integration is an open question for future studies.
71
Somatosensory saccades reveal the timing of tactile spatial remapping
TL;DR: The difference between saccade onset latencies of crossed and uncrossed hand postures, and between the onset of a turn-around saccades and a straight sAccade in the crossed hand posture, are proposed to reveal the timing of tactile spatial remapping.
61
A review of grasping as the movements of digits in space
TL;DR: This review develops a new description of the speed-accuracy trade-off for multiple effectors that is applied to grasping and concludes that treating grasping as movements of the digits in space is a more suitable basis for understanding the neural control of grasping.
Ultra-fast selection of grasping points.
TL;DR: Subjects grasped a ball or a cube that sometimes rotated briefly when the digits started moving and altered their choice of grasping points so that the digits ended at different positions on the rotated surface of the ball, and the ball was grasped with the preferred orientation of the hand.
36
Collision Avoidance of Arbitrarily Shaped Deforming Objects Using Collision Cones
Vishwamithra Sunkara,Animesh Chakravarthy,Debasish Ghose +2 more
- 20 Feb 2019
TL;DR: In this letter, the problem of collision avoidance of objects, which can deform by changing their shape as a function of time, is considered and the notion of collision cone equations are embedded in a Lyapunov framework and used to develop nonlinear analytical guidance laws for collision avoidance in such environments.
31
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