Neuroimaging of emotion:: empirical effects of proportional global signal scaling in fMRI data analysis
Neuroimaging of emotion:: empirical effects of proportional global signal scaling in fMRI data analysis
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DOI：
10.1016/j.neuroimage.2004.12.011
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发表时间：
2005-04-01
期刊：
影响因子：
5.7
通讯作者：
Vaitl, D
中科院分区：
文献类型：
--
作者：
Junghöfer, M;Schupp, HT;Vaitl, D
BOLD-fMRI信号的全局变化通常被认为是滋扰效应。通常使用比例全局信号缩放（PGSS）来消除这种不需要的方差源。然而，PGSS的应用依赖于BOLD信号的全局变化与实验条件不相关的假设。对于认知任务，研究表明，不合理地应用PGSS可能会极大地扭曲统计结果。本研究在情绪研究领域探讨了这个问题。具体来说，功能磁共振成像数据是在一个块设计，而21名受试者被动地观看高和低情绪唤起愉快，不愉快，和中性的图片。违反正交性假设被发现的情绪图片高唤醒的分析，导致显着不同的结果相比，没有PGSS进行分析。PGSS的应用与视觉皮层区域的情感激活减弱、边缘系统和旁边缘系统区域对情感激活不敏感以及广泛分布的人工失活有关。与此相反，正交性假设不违反低唤起情感材料。因此，使用PGSS的有效性变化的功能的刺激的情绪唤起。两者合计，PGSS的不当使用可能会导致相互矛盾的结果，在情感神经科学功能磁共振成像研究，特别是关于边缘和边缘结构。(c)2004年爱思唯尔公司All rights reserved.
Global variations of BOLD-fMRI signal are often considered as nuisance effects. This unwanted source of variance is commonly eliminated using proportional global signal scaling (PGSS). However, application of PGSS relies on the assumption that global variations of BOLD signal and experimental conditions are uncorrelated. It has been shown for cognitive tasks that the unjustified application of PGSS might greatly distort statistical results. The present study examined this issue in the domain of emotion research. Specifically, fMRI data were obtained in a block-design, while 21 subjects passively viewed high and low emotionally arousing pleasant, unpleasant, and neutral pictures. Violations of the orthogonality assumption were found for analyses of emotional pictures high in arousal, causing dramatically different outcomes when compared to analyses performed without PGSS. Application of PGSS was associated with attenuated emotional activation in visual cortical areas, insensitivity to emotional activations in limbic and paratimbic regions, and widely distributed artificial deactivations. In contrast, the orthogonality assumption was not violated for low arousing emotional materials. Thus, the validity of using PGSS varied as a function of the emotional arousal of the stimuli. Taken together, the unwarranted use of PGSS might contribute to conflicting results in affective neuroscience fMRI studies, in particular with respect to limbic and paralimbic structures. (c) 2004 Elsevier Inc. All rights reserved.