Friston K J, Holmes A P, Price C J, Büchel C, Worsley K J
The Wellcome Department of Cognitive Neurology, Institute of Neurology, Queen Square, London, WC1N 3BG, United Kingdom.
Neuroimage. 1999 Oct;10(4):385-96. doi: 10.1006/nimg.1999.0484.
In this paper we present an approach to making inferences about generic activations in groups of subjects using fMRI. In particular we suggest that activations common to all subjects reflect aspects of functional anatomy that may be "typical" of the population from which that group was sampled. These commonalities can be identified by a conjunction analysis of the activation effects in which the contrasts, testing for an activation, are specified separately for each subject. A conjunction is the joint refutation of multiple null hypotheses, in this instance, of no activation in any subject. The motivation behind this use of conjunctions is that fixed-effect analyses are generally more "sensitive" than equivalent random-effect analyses. This is because fixed-effect analyses can harness the large degrees of freedom and small scan-to-scan variability (relative to the variability in responses from subject to subject) when assessing the significance of an estimated response. The price one pays for the apparent sensitivity of fixed-effect analyses is that the ensuing inferences pertain to, and only to, the subjects studied. However, a conjunction analysis, using a fixed-effect model, allows one to infer: (i) that every subject studied activated and (ii) that at least a certain proportion of the population would have shown this effect. The second inference depends upon a meta-analytic formulation in terms of a confidence region for this proportion. This approach retains the sensitivity of fixed-effect analyses when the inference that only a substantial proportion of the population activates is sufficient.
在本文中，我们提出了一种利用功能磁共振成像（fMRI）对一组受试者的一般激活情况进行推断的方法。具体而言，我们认为所有受试者共有的激活反映了功能解剖学的某些方面，这些方面可能是该组受试者所抽取人群的“典型”特征。这些共性可以通过对激活效应进行联合分析来识别，其中针对每个受试者分别指定用于检验激活的对比。联合是对多个零假设的联合反驳，在这种情况下，是对任何受试者均无激活的零假设的反驳。这种使用联合的背后动机是，固定效应分析通常比等效的随机效应分析更“敏感”。这是因为在评估估计反应的显著性时，固定效应分析可以利用大量的自由度和较小的逐次扫描变异性（相对于受试者间反应的变异性）。为固定效应分析的明显敏感性所付出的代价是，随之而来的推断仅适用于所研究的受试者。然而，使用固定效应模型的联合分析允许人们推断：（i）所研究的每个受试者都被激活；（ii）至少有一定比例的人群会表现出这种效应。第二个推断取决于关于该比例的置信区域的元分析公式。当仅推断出相当比例的人群被激活就足够时，这种方法保留了固定效应分析的敏感性。
