FINE TIMING OF THE BOLD HEMODYNAMIC RESPONSE

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 我们从以前的研究中获得的数据集表明，由于刺激强度的差异，BOLD发作时间存在很大（> 200 msec）差异：较强的反应可能比较弱的反应更早开始。虽然刺激强度（如对比度幅度）被认为会导致LGN（Hartveit and Heggelund 1992）、V1（赖希et al 2001）和其他视觉区域（Gawne et al 1996）神经反应的小的起始时间差异，但这些小的时间差异（10毫秒）比我们在BOLD fMRI反应中看到的小一个数量级。我们建议使用具有短TR的fMRI序列对BOLD响应的时间进行精细测量，每250毫秒收集一个体积。如果作为反应强度的函数存在时间差异，它们将在该领域产生重大影响，因为越来越多的研究正在使用fMRI研究神经反应的时间。时间差异也可能影响使用动态因果建模（DCM）的工作，其中时间用于推断皮质区域之间的因果联系（Stephan et al 2008，Mechelli et al 2003）。这里获得的数据将是几个拨款建议，建议使用功能磁共振成像和联合功能磁共振成像/脑电图研究知觉过程的时间的关键。恩格尔、奥尔曼、克尔斯滕和他都有兴趣或正在发展的建议，其中这种定时测量可能会发挥重要作用。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Data sets we have obtained from previous studies suggest a large (> 200 msec) difference in BOLD onset timing due to differences in stimulus strength: stronger responses may begin earlier than weaker ones. Although stimulus strength (such as contrast amplitude) is thought to result in small onset timing differences in the neural response in the LGN (Hartveit and Heggelund 1992), V1 (Reich et al 2001), and other visual areas (Gawne et al 1996), these small timing differences (10's of msec) are an order of magnitude smaller than what we have seen in the BOLD fMRI response. We propose to make fine measurements of the timing of the BOLD response using an fMRI sequence with a short TR, gathering one volume every 250 milliseconds. Should timing differences as a function of response strength exist, they would have a substantial impact in the field, as an increasing number of studies are investigating timing of neural response using fMRI. The timing differences may also impact work using dynamic causal modeling (DCM), in which timing is used to infer causal links between cortical areas (Stephan et al 2008, Mechelli et al 2003). The data obtained here will be key for several grant proposals which propose to use fMRI and joint fMRI/EEG to study timing of perceptual processes. Engel, Olman, Kersten, and He all have interests or proposals under development in which such measurements of timing may play an important role.