Hemispheric asymmetry in global/local processing: Effects of stimulus position and spatial frequency
Hemispheric asymmetry in global/local processing: Effects of stimulus position and spatial frequency
复制标题
DOI：
10.1006/nimg.2002.1255
复制
发表时间：
2002-11-01
期刊：
影响因子：
5.7
通讯作者：
Woods, DL
中科院分区：
文献类型：
--
作者：
Han, SH;Weaver, JA;Woods, DL
通过功能磁共振成像（functional magnetic resonance imaging，MRI）测量脑血流动力学反应，探讨了大脑半球在处理分层刺激的全局和局部信息时功能不对称的神经机制。在选择性注意任务中，受试者在全局或局部水平上对复合字母的目标做出反应，这些复合字母是（1）空间频率谱中的宽带，并在固定时呈现;（2）宽带，并随机呈现在固定的左侧或右侧;或（3）对比度平衡（CB），以去除低空间频率（SF），并在固定时呈现。中央宽带刺激诱导更强的激活在右中枕叶皮层下的全球相对于本地的注意条件，但在左下枕叶皮层，更强的激活诱导下，本地相对于全球的注意条件。枕叶皮质的不对称性被单侧呈现和对比度平衡所削弱。结果表明，复合刺激的位置和SF谱对整体加工和局部加工的偏侧化具有调制作用。在所有的刺激条件下，相对于局部注意，整体注意对内侧枕叶皮层的激活也更强。这些影响的性质进行了讨论。(C)2002 Elsevier Science（美国）。
We examined the neural mechanisms of functional asymmetry between hemispheres in the processing of global and local information of hierarchical stimuli by measuring hemodynamic responses with functional magnetic resonance imaging (MRI). In a selective attention task, subjects responded to targets at the global or local level of compound letters that were (1) broadband in spatial-frequency spectrum and presented at fixation; (2) broadband and presented randomly to the left or the right of fixation; or (3) contrast balanced (CB) to remove low spatial frequencies (SFs) and presented at fixation. Central broadband stimuli induced stronger activation in the right middle occipital cortex under global relative to local attention conditions but in the left inferior occipital cortex, stronger activation was induced under local relative to global attention conditions. The asymmetry over the occipital cortex was weakened by unilateral presentation and by contrast balancing. The results indicate that the lateralization of global and local processing is modulated by the position and SF spectrum of the compound stimuli. The global attention also produced stronger activation over the medial occipital cortex relative to the local attention under all the stimulus conditions. The nature of these effects is discussed. (C) 2002 Elsevier Science (USA).