Robson M D, Dorosz J L, Gore J C
Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520-8042, USA.
Neuroimage. 1998 Apr;7(3):185-98. doi: 10.1006/nimg.1998.0322.
Averaged single trials (AST) allowed the functional magnetic resonance imaging (fMRI) response to auditory stimuli to be measured at high temporal (1 s) and spatial (0.1 cm3) resolution. Using this paradigm we investigated the transient signal response to 100-ms tone bursts in trains of between 100 ms and 25.5 s in total duration. We have demonstrated that the fMRI response to such auditory stimuli is approximately linear for trains of 6 s and longer, but that shorter stimuli produce signals that are larger than might be expected from the response to the longer stimuli. This nonlinear behavior can be modeled if an adaptive response to each stimulus is assumed. A study using a novel paradigm was also performed in order to study the influence of scanner noise during fMRI experiments on the auditory system response to tones. This study demonstrated that the temporal response to 700-ms tone stimuli is modified when performed in the presence of scanner gradient noise, the modification being a small but significant increase (P < 0.05) in the magnitude of the response. Finally the ability to measure the onset of functional activation using the AST method was examined. It was found, with the aid of computer simulation that a sampling rate of one image per second is adequate to distinguish temporal responses. Using the data acquired in this study, onset times were calculated for the auditory cortex, and these results are consistent with current models of functional activation.
平均单次试验（AST）能够在高时间分辨率（1秒）和空间分辨率（0.1立方厘米）下测量功能磁共振成像（fMRI）对听觉刺激的反应。使用这种范式，我们研究了对总时长在100毫秒至25.5秒之间的一系列100毫秒音调脉冲的瞬态信号反应。我们已经证明，对于时长为6秒及更长的一系列刺激，fMRI对这种听觉刺激的反应近似呈线性，但较短的刺激产生的信号比根据对较长刺激的反应所预期的要大。如果假设对每个刺激有适应性反应，那么这种非线性行为是可以建模的。还进行了一项使用新范式的研究，以探讨fMRI实验期间扫描仪噪声对听觉系统对音调反应的影响。这项研究表明，在存在扫描仪梯度噪声的情况下进行实验时，对700毫秒音调刺激的时间反应会发生改变，这种改变是反应幅度有小幅但显著的增加（P < 0.05）。最后，研究了使用AST方法测量功能激活起始的能力。借助计算机模拟发现，每秒一幅图像的采样率足以区分时间反应。利用本研究中获取的数据，计算了听觉皮层的起始时间，这些结果与当前的功能激活模型一致。
