Hughes Laura E, Bates Timothy C, Aimola Davies Anne M
Macquarie Centre for Cognitive Science, Macquarie University, Sydney, Australia.
Brain Cogn. 2005 Oct;59(1):71-81. doi: 10.1016/j.bandc.2005.05.003. Epub 2005 Jul 12.
The line-bisection task, adapted to utilise a wooden rod as the bisection stimulus, has revealed that patients with visuo-spatial neglect may be more accurate at bisection when asked to pick up the rod, compared to pointing to its centre. We recently reported that neurologically intact participants show a similar dissociation on this task-demonstrating a rightward bias when pointing to the centre, which was not present when grasping the rod by the centre. The current paper examined how pointing and grasping responses were affected by adapted rod-bisection tasks that emphasised local or global processing. In Experiment 1, 26 participants completed four rod-bisection tasks. The rods were compound stimuli and the participants directed to focus on either the local or global level. The results demonstrated that when participants focused on the global level, the previous dissociations found for pointing and grasping conditions were evident. However, the perception of centre did change when participants focused on the local level: both the pointing and grasping responses were rightward biased. In Experiment 2, 42 participants completed three bisection tasks which again emphasised either the local or global level, but in different sets of stimuli. The results of this task further support the findings in Experiment 1: the rightward bias in the local-bisection task was again evident and in addition, the global-bisection task resulted in no bias and no difference between the pointing and grasping bisections. These results demonstrate how task demands can similarly affect the pointing and grasping responses, and indicate that local and global processing may be involved in perception/action dissociations on rod bisection.
将用于二分刺激的木杆进行改良后的直线二等分任务表明，与指向木杆中心相比，患有视觉空间忽视症的患者在被要求拿起木杆时，二等分的准确性可能更高。我们最近报告称，神经功能正常的参与者在这项任务中也表现出类似的分离现象——指向中心时表现出向右的偏差，而握住木杆中心时则不存在这种偏差。本文研究了强调局部或整体加工的改良木杆二等分任务如何影响指向和抓握反应。在实验1中，26名参与者完成了四项木杆二等分任务。木杆是复合刺激物，要求参与者关注局部或整体水平。结果表明，当参与者关注整体水平时，之前在指向和抓握条件下发现的分离现象很明显。然而，当参与者关注局部水平时，中心的感知确实发生了变化：指向和抓握反应都向右偏斜。在实验2中，42名参与者完成了三项二等分任务，这些任务同样强调局部或整体水平，但使用了不同的刺激组。这项任务的结果进一步支持了实验1的结果：局部二等分任务中的向右偏差再次明显，此外，整体二等分任务没有偏差，指向和抓握二等分之间也没有差异。这些结果表明任务要求如何同样影响指向和抓握反应，并表明局部和整体加工可能参与了木杆二等分的感知/行动分离。
