Power Analysis and Optimization for FMRI Experiments

在广泛使用的功能磁共振方法中， 成像（fMRI），权力的正式控制（即，1-假阴性率） 在假阳性率方面，的控制 功率是必要的，以量化负fMRI结果的信心，在这两个 基本的科学和临床设置。一个突出的例子， 能够通过先验功率通知fMRI实验设计的效用 在神经外科手术的术前功能磁共振成像测试中， 功能定位的候选人。显然，在这种情况下， 阴性可能对患者产生不良后果。在基础科学中， fMRI实验的先验功率计算将提供以下能力： 用一种期望的方法来反驳基于负面结果的大脑认知模型， 信心具体目标1是制定用于确定 参数的逐体素功率（即，t和F）检验。相比之下 与以前的方法相比，该算法将考虑时间 噪声的自相关结构，完整的实验设计， 感兴趣的假设，假设的信噪比，以及滤波 神经活动到功能磁共振成像转换的特性。具体目标二是 研究神经活动转换的饱和特性 fMRI信号的变化。更好的饱和度表征将 改善fMRI效应幅度的预测，从而提高 电力计算在有意义的生理范围内的饱和度将 通过测试与fMRI响应叠加的偏差来检查（在 初级感觉运动和早期视觉区域）由一组，两组， 或三个紧密间隔的（1秒视觉刺激。具体目标3是 研究事件相关功能磁共振成像设计的功效对 的时间结构。 提高实验设计功效的能力 通过操纵它们的时间结构（不改变成本）， 使高功率fMRI实验更可行。

In the widely used methodology of functional magnetic resonance imaging (fMRI), the formal control of power (i.e., 1-false-negative rate) has received less attention than the control of false-positive rate. The control of power is necessary for quantifying confidence in negative fMRI results in both basic scientific and clinical settings. A striking example of the clinical utility of being able to inform fMRI experimental design by a priori power calculations is in pre-operative fMRI testing of neurological surgery candidates for localization of function. Clearly in such circumstances a false negative could have undesirable consequences for the patient. In basic science, a priori power calculations for fMRI experiments would afford the ability to refute brain-cognition models based on negative results with a desired confidence. Specific Aim 1 is to formulate an algorithm for determining voxel-wise power of parametric (i.e., t and F) tests on fMRI data. In contrast to previous methods, this algorithm will account for the temporal autocorrelation structure of the noise, the complete experimental design, the hypothesis of interest, assumed signal:noise ratios, and the filtering properties of the neural activity-to-fMRI transform. Specific Aim 2 is to investigate saturation characteristics of the transformation of neural activity change to fMRI signal change. Better characterization of saturation will improve predictions of fMRI effect magnitude and hence improve the accuracy of power calculations. Saturation over meaningful physiological ranges will be examined by testing for deviations from superposition of fMRI responses (in primary sensori-motor and early visual regions) elicited by sets of one, two, or three closely spaced (1 sec visual stimuli. Sepcific Aim 3 is to investigate the dependence of the power of event-related fMRI designs on their temporal structure. The ability to improve power of experimental designs by manipulation of their temporal structure (without changing the cost) will make high power fMRI experiments more feasible.