Deconvolution of event-related fMRI responses in fast-rate experimental designs: Tracking amplitude variations
Deconvolution of event-related fMRI responses in fast-rate experimental designs: Tracking amplitude variations
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DOI：
10.1162/089892900564082
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发表时间：
2000-01-01
影响因子：
3.2
通讯作者：
Heinze, HJ
中科院分区：
文献类型：
--
作者：
Hinrichs, H;Scholz, M;Heinze, HJ
事件相关功能磁共振成像的最新发展极大地扩展了实验设计的范围。如果事件快速连续发生，则相应的时间锁定响应会显著重叠，需要进行去卷积，以便分离不同事件的贡献。在这里，我们提出了一个去卷积的方法，这是特别针对功能磁共振成像数据的序列或上下文相关的反应是预期的分析。为此，我们假设血流动力学响应函数（HDR）具有恒定但未预定义的形状，但可能具有可变的振幅。这种方法减少了要估计的变量的数量，但仍然保持解决方案的灵活性，相对于形状。因此，提高了统计效率。HDR强度的时间变化直接由算法导出的幅度指示。通过改进的噪声协方差估计，进一步支持估计效率和统计推断。使用合成的数据集，正确识别了不同形状的HDR和不同的振幅因子。统计灵敏度的提高提高了这些数据中合成激活的假阳性和真阳性检测率的比率。在与人类受试者的事件相关的功能磁共振成像实验中，不同的HDR振幅可以对应于不同视觉刺激对比度的刺激而导出。最后，在视觉空间注意实验中，我们获得了不同的fMRI反应幅度取决于顺序的注意条件。
Recent developments towards event-related functional magnetic resonance imaging has greatly err-ended the range of experimental designs. If the events occur in rapid succession, the corresponding time-locked responses overlap significantly and need to be deconvolved in order to separate the contributions of different events. Here we present a deconvolution approach, which is especially aimed at the analysis of fMRI data where sequence- or context-related responses are expected. For this purpose, we make the assumption of a hemodynamic response function (HDR) with constant yet not predefined shape but with possibly variable amplitudes. This approach reduces the number of variables to be estimated but still keeps the solutions flexible with respect to the shape. Consequently, statistical efficiency is improved. Temporal variations of the HDR strength are directly indicated by the amplitudes derived by the algorithm. Both the estimation efficiency and statistical inference are further supported by an improved estimation of the noise covariance. Using synthesized data sets, both differently shaped HDRs and varying amplitude factors were correctly identified. The gain in statistical sensitivity led to improved ratios of false- and true-positive detection rates for synthetic activations in these data. In an event-related fMRI experiment with a human subject, different HDR amplitudes could be derived corresponding to stimulation at different visual stimulus contrasts. Finally, in a visual spatial attention experiment we obtained different fMRI response amplitudes depending on the sequences of attention conditions.