Büchel C, Holmes A P, Rees G, Friston K J
The Wellcome Department of Cognitive Neurology, Institute of Neurology, Queen Square, London, WC1N 3BG, United Kingdom.
Neuroimage. 1998 Aug;8(2):140-8. doi: 10.1006/nimg.1998.0351.
Parametric study designs proved very useful in characterizing the relationship between experimental parameters (e.g., word presentation rate) and regional cerebral blood flow in positron emission tomography studies. In a previous paper we presented a method that fits nonlinear functions of stimulus or task parameters to hemodynamic responses, using second-order polynomial expansions. Here we expand this approach to model nonlinear relationships between BOLD responses and experimental parameters, using fMRI. We present a framework that allows this technique to be implemented in the context of the general linear model employed by statistical parametric mapping (SPM). Statistical inferences, in this instance, are based on F statistics and in this respect we emphasize the use of corrected P values for F fields (i.e., SPM¿F¿). The approach is illustrated with a fMRI study that looked at the effect of increasing auditory word-presentation rate. Our parametric design allowed us to characterize different forms of rate-dependent responses in three critical regions: (i) bilateral frontal regions showed a categorical response to the presence of words irrespective of rate, suggesting a role for this region in establishing cognitive (e.g., attentional) set; (ii) in bilateral occipitotemporal regions activations increased linearly with increasing word rate; and (iii) posterior auditory association cortex exhibited a nonlinear (inverted U) relationship to word rate.
在正电子发射断层扫描研究中，参数研究设计被证明在表征实验参数（如单词呈现速率）与局部脑血流量之间的关系方面非常有用。在之前的一篇论文中，我们提出了一种方法，该方法使用二阶多项式展开将刺激或任务参数的非线性函数拟合到血流动力学反应。在这里，我们扩展这种方法，使用功能磁共振成像（fMRI）来模拟血氧水平依赖（BOLD）反应与实验参数之间的非线性关系。我们提出了一个框架，使这种技术能够在统计参数映射（SPM）所采用的一般线性模型的背景下得以实现。在这种情况下，统计推断基于F统计量，在这方面，我们强调对F场（即SPM“F”）使用校正后的P值。通过一项fMRI研究对该方法进行了说明，该研究考察了增加听觉单词呈现速率的效果。我们的参数设计使我们能够在三个关键区域表征不同形式的速率依赖性反应：（i）双侧额叶区域对单词的存在表现出分类反应，而与速率无关，这表明该区域在建立认知（如注意力）定势方面发挥作用；（ii）在双侧枕颞区域，激活随着单词速率的增加而线性增加；（iii）后听觉联合皮层与单词速率呈现非线性（倒U形）关系。
