Zhang Xin, Han ShiHui
Department of Psychology, Peking University, Beijing 100871, China.
Sci China C Life Sci. 2007 Aug;50(4):557-65. doi: 10.1007/s11427-007-0067-4.
Previous research suggests that the right and left hemispheres dominate global and local perception of hierarchical patterns, respectively. The current work examined whether global perception of hierarchical stimuli requires coherent work of bilateral visual cortices using transcranial magnetic stimulation (TMS). Subjects discriminated global or local properties of compound letters in Experiment 1. Reaction times were recorded when single-pulse real TMS or sham TMS was delivered over the left or right visual cortex. While a global precedence effect (i.e., faster responses to global than local targets and stronger global-to-local interference than the reverse) was observed, TMS decreased global-to-local interference whereas increased local-to-global interference. Experiment 2 ruled out the possibility that the effects observed in Experiment 1 resulted from perceptual learning. Experiment 3 used compound shapes and observed TMS effect similar to that in Experiment 1. Moreover, TMS also slowed global RTs whereas speeded up local RTs in Experiment 3. Finally, the TMS effects observed in Experiments 1 and 3 did not differ between the conditions when TMS was applied over the left and right hemispheres. The results support a coherence hypothesis that global perception of compound stimuli depends upon the coherent work of bilateral visual cortices.
先前的研究表明，左右半球分别主导着对层次模式的整体和局部感知。目前的研究使用经颅磁刺激（TMS）来检验对层次刺激的整体感知是否需要双侧视觉皮层的协同工作。在实验1中，受试者辨别复合字母的整体或局部属性。当在左侧或右侧视觉皮层施加单脉冲真实TMS或伪TMS时，记录反应时间。虽然观察到了整体优先效应（即对整体目标的反应比对局部目标更快，且整体到局部的干扰比相反情况更强），但TMS减少了整体到局部的干扰，而增加了局部到整体的干扰。实验2排除了实验1中观察到的效应是由感知学习导致的可能性。实验3使用复合形状，并观察到了与实验1类似的TMS效应。此外，在实验3中，TMS还减慢了整体反应时间，而加快了局部反应时间。最后，在实验1和实验3中观察到的TMS效应在TMS施加于左半球和右半球的条件下没有差异。这些结果支持了一个连贯性假设，即对复合刺激的整体感知依赖于双侧视觉皮层的协同工作。
