Global perception depends on coherent work of bilateral visual cortices: Transcranial magnetic stimulation (TMS) studies  

作　　者：ZHANG Xin1 & HAN ShiHui1,2 1 Department of Psychology, Peking University, Beijing 100871, China 2 Learning & Cognition Lab, Capital Normal University, Beijing 100875, China 

出　　处：《Science China(Life Sciences)》2007年第4期557-565,共9页中国科学（生命科学英文版）

基　　金：Supported by the National Natural Science Foundation of China (Grant Nos. 30630025, 30225026, and 30328016);the Ministry of Science and Technology of China (Grant No. 2002CCA01000)

摘　　要：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 hierarchi-cal 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 co-herent work of bilateral visual cortices.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 hierarchi-cal 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 co- herent work of bilateral visual cortices.

关 键 词：GLOBAL PERCEPTION VISUAL cortex TRANSCRANIAL magnetic stimulation (TMS) compound STIMULUS 

分 类 号：Q42[生物学—神经生物学]