Characterizing the hemodynamic response: Effects of presentation rate, sampling procedure, and the possibility of ordering brain activity based on relative timing
Characterizing the hemodynamic response: Effects of presentation rate, sampling procedure, and the possibility of ordering brain activity based on relative timing
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DOI：
10.1006/nimg.2000.0568
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发表时间：
2000-06-01
期刊：
影响因子：
5.7
通讯作者：
Buckner, RL
中科院分区：
文献类型：
--
作者：
Miezin, FM;Maccotta, L;Buckner, RL
快速呈现事件相关功能MRI （ER-fMRI）允许基于血流动力学的神经成像方法采用典型认知设置的行为任务范式。然而，血流动力学反应的迟滞及其变化限制了ER-fMRI的应用。在一系列的两项研究中，对主要视觉和运动皮层或其附近的血流动力学反应的估计进行了比较，以确定ER-fMRI程序的局限性，更一般地说，是为了描述血流动力学反应的行为。通过在一般线性模型中求解一组线性方程，估计了重叠事件中血流动力学反应的时间剖面。在解方程时没有对形状作任何假设。在对时间剖面进行估计之后，使用伽马函数对振幅和时序进行建模。结果表明：(1)在一个区域内，对于给定的受试者，从一系列测量到下一系列测量，血流动力学响应的估计在振幅（r(2) = 0.98）和峰值时间（r(2) = 0.95）方面都是非常稳定的，而在估计开始时间（r(2) = 0.60）方面则稍不稳定。(2)随着试验呈现率的变化（从间隔20 s的试验到时间重叠的试验），血流动力学反应幅度呈现小而显著的下降。间隔（平均）5秒的试验发作幅度比间隔20秒的试验发作幅度减少17-25%。功率分析表明，如果目标是统计可靠的响应检测，则快速试验次数的增加超过幅度的减少。(3)一个区域的血流动力学反应的幅度和时间的知识无法预测另一个区域的这些特性，即使在受试者内部比较中也是如此。(4)在受试者中，反应幅度与反应时间没有显著的相关性，无论是对开始时间还是峰值时间的估计。(5)响应的区域内稳定性足以允许在响应时间上检测到小于一秒的偏移，从而使与事件相关的fMRI方法能够回答有关区域之间相对时间变化的问题。(C) 2000年学术出版社。
Rapid-presentation event-related functional MRI (ER-fMRI) allows neuroimaging methods based on hemodynamics to employ behavioral task paradigms typical of cognitive settings. However, the sluggishness of the hemodynamic response and its variance provide constraints on how ER-fMRI can be applied. In a series of two studies, estimates of the hemodynamic response in or near the primary visual and motor cortices were compared across various paradigms and sampling procedures to determine the limits of ER-fMRI procedures and, more generally, to describe the behavior of the hemodynamic response, The temporal profile of the hemodynamic response was estimated across overlapping events by solving a set of linear equations within the general linear model. No assumptions about the shape were made in solving the equations. Following estimation of the temporal profile, the amplitude and timing were modeled using a gamma function. Results indicated that (1) within a region, for a given subject, estimation of the hemodynamic response is extremely stable for both amplitude (r(2) = 0.98) and time to peak (r(2) = 0.95), from one series of measurements to the next, and slightly less stable for estimation of time to onset (r(2) = 0.60). (2) As the trial presentation rate changed (from those spaced 20 s apart to temporally overlapping trials), the hemodynamic response amplitude showed a small, but significant, decrease. Trial onsets spaced (on average) 5 s apart showed a 17-25% reduction in amplitude compared to those spaced 20 s apart. Power analysis indicated that the increased number of trials at fast rates outweighs this decrease in amplitude if statistically reliable response detection is the goal. (3) Knowledge of the amplitude and timing of the hemodynamic response in one region failed to predict those properties in another region, even for within-subject comparisons. (4) Across subjects, the amplitude of the response showed no significant correlation with timing of the response, for either time-to-onset or time-to-peak estimates. (5) The within-region stability of the response was sufficient to allow offsets in the timing of the response to be detected that were under a second, placing event-related fMRI methods in a position to answer questions about the change in relative timing between regions. (C) 2000 Academic Press.