Continuous carry-over designs for fMRI
Continuous carry-over designs for fMRI
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DOI：
10.1016/j.neuroimage.2007.02.005
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发表时间：
2007-05-01
期刊：
影响因子：
5.7
通讯作者：
Aguirre, Geoffrey Karl
中科院分区：
文献类型：
--
作者：
Aguirre, Geoffrey Karl
本文描述了连续的fMRI结转实验。在这些研究中，刺激以一种不间断的、连续的方式呈现，可以用来同时估计刺激之间神经活动的平均差异，以及一个刺激对另一个刺激的影响（结转效应）。神经适应是最近许多功能磁共振成像研究的基础，它被证明是一种特殊形式的结转效应。用这种方法，刺激的适应效应可以在一个连续的序列中进行研究，而不是在孤立的对或块中进行研究。此外，刺激对神经反应的平均直接影响可以形成同时获得的分布式模式分析的基础，允许在焦点（体素内）和分布（跨体素）空间尺度上比较神经种群编码。这些研究理想地采用连续平衡的顺序进行，其中每个刺激都先于其他刺激并紧随其后。虽然m序列可以提供这种刺激顺序，但Finney和Outhwaite的I型索引I序列可以用于那些不存在m序列解决方案的实验设计的fMRI研究。连续平衡序列的连续携带设计被认为特别适合“相似空间”的表征，在这种空间中，刺激的感知相似性与体素内部和跨体素的神经表征结构有关。这些概念用一个涉及颜色的神经表征的工作示例来说明。结果表明，单次扫描的数据足以检测到直接和携带效应，并证明了神经放电分布模式的相似性结构与一组颜色的感知相似性的对应关系。(c) 2007爱思唯尔公司版权所有。
This paper describes continuous carry-over fMRI experiments. In these studies, stimuli are presented in an unbroken, sequential manner, and can be used to estimate simultaneously the mean difference in neural activity between stimuli as well as the effect of one stimulus upon another (carry-over effects). Neural adaptation, which has been the basis of many recent fMRI studies, is shown to be a specific form of carry-over effect. With this approach, the adapting effects of stimuli may be studied in a continuous sequence, as opposed to within isolated pairs or blocks. Additionally, the average, direct effect of a stimulus upon neural response can form the basis of a simultaneously obtained distributed pattern analysis, allowing comparison of neural population coding on focal (within voxel) and distributed (across voxel) spatial scales. These studies are ideally conducted with serially balanced sequences, in which every stimulus precedes and follows every other stimulus. While m-sequences can provide this stimulus order, the type I index I sequence of Finney and Outhwaite may be used in fMRI studies for those experimental designs for which an m-sequence solution does not exist. Continuous carry-over designs with serially balanced sequences are argued to be particularly well suited to the characterization of "similarity spaces," in which the perceptual similarity of stimuli is related to the structure of neural representation both within and across voxels. These concepts are illustrated with a worked example involving the neural representation of color. It is shown that data from a single scanning session are sufficient to detect direct and carry-over effects, as well as demonstrate the correspondence of the similarity structure of distributed patterns of neural firing and the perceptual similarity of a set of colors. (c) 2007 Elsevier Inc. All rights reserved.