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.
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)
