| Popis: |
Performing goal-directed hand-movements in the presence of obstacles is a task that we usually complete successfully many times a day without much conscious consideration. Yet, little is known about the underlying processes. The aim of this thesis was to investigate the role of perceptual, motor and cognitive constraints on obstacle avoidance during reaching. To do this a tabletop-based obstacle avoidance setup and motiontracking were used. In the first experimental chapter, the previously reported tendency of participants to select movement paths that pass roughly through the mid-point between two obstacles was examined. The starting position of the hand and the availability of visual feedback were manipulated and evidence was found that movement path selection depends on both a collision-avoidance strategy and the associated biomechanical costs; even when visual feedback is unavailable. The second experimental chapter investigated an action-blindsight phenomenon, specifically the ability of cortically blind patients to avoid unseen obstacles. It was found that only two out of the six patients tested potentially showed some residual sensitivity to obstacles in their blind visual field. The final two experimental chapters went further to examine the role of perceptual information and attentional mechanisms respectively. It was found that during obstacle avoidance participants predominantly look at the movement target and rarely towards any obstacles or their moving hand. Furthermore, they tend to move their hand away from obstacles that are fixated. Finally, it was also found that a concurrent attentional task affected movement path selection in a similar way. At present it is unclear whether these perceptual and attentional effects are additive or independent of each other. Overall, these findings suggest that both conscious visual information and attentional mechanisms are crucial factors in determining movement path selection during obstacle avoidance in reaching. |
