Department of Physical Therapy, Marquette University, P.O. Box 1881, Milwaukee, WI 53201-1881, USA.
Magn Reson Imaging. 2013 Sep;31(7):1119-28. doi: 10.1016/j.mri.2013.02.009. Epub 2013 May 1.
The use of canonical functions to model BOLD-fMRI data in people post-stroke may lead to inaccurate descriptions of task-related brain activity. The purpose of this study was to determine whether the spatiotemporal profile of hemodynamic responses (HDRs) obtained from stroke survivors during an event-related experiment could be used to develop individualized HDR functions that would enhance BOLD-fMRI signal detection in block experiments. Our long term goal was to use this information to develop individualized HDR functions for stroke survivors that could be used to analyze brain activity associated with locomotor-like movements. We also aimed to examine the reproducibility of HDRs obtained across two scan sessions in order to determine whether data from a single event-related session could be used to analyze block data obtained in subsequent sessions. Results indicate that the spatiotemporal profile of HDRs measured with BOLD-fMRI in stroke survivors was not the same as that observed in individuals without stroke. We observed small between-group differences in the rates of rise and decline of HDRs that were more apparent in individuals with cortical as compared to subcortical stroke. There were no differences in the peak or time to peak of HDRs in people with and without stroke. Of interest, differences in HDRs were not as substantial as expected from previous reports and were not large enough to necessitate the use of individualized HDR functions to obtain valid measures of movement-related brain activity. We conclude that all strokes do not affect the spatiotemporal characteristics of HDRs in such a way as to produce inaccurate representations of brain activity as measured by BOLD-fMRI. However, care should be taken to identify individuals whose BOLD-fMRI data may not provide an accurate representation of underlying brain activation when canonical models are used. Examination of HDRs need not be done for each scan session, as our data suggest that the characteristics of HDRs in stroke survivors are reproducible across days.
在中风后人群中使用正则函数对 BOLD-fMRI 数据进行建模可能会导致对与任务相关的大脑活动的描述不准确。本研究的目的是确定从事件相关实验中获得的中风幸存者的血液动力学反应 (HDR) 的时空分布是否可用于开发个性化 HDR 功能，从而增强块实验中的 BOLD-fMRI 信号检测。我们的长期目标是使用这些信息为中风幸存者开发个性化的 HDR 功能，以便分析与类似运动的运动相关的大脑活动。我们还旨在检查在两个扫描会话中获得的 HDR 的可重复性，以确定是否可以使用单个事件相关会话的数据来分析随后会话中获得的块数据。结果表明，在中风幸存者中使用 BOLD-fMRI 测量的 HDR 的时空分布与在没有中风的个体中观察到的分布不同。我们观察到，与皮质中风相比，皮质中风患者的 HDR 上升和下降速率之间的组间差异较小。在患有和不患有中风的个体中，HDR 的峰值或达到峰值的时间没有差异。有趣的是，HDR 之间的差异并不像以前的报告所预期的那样大，也不足以需要使用个性化的 HDR 功能来获得运动相关大脑活动的有效测量。我们得出的结论是，并非所有中风都会以导致 BOLD-fMRI 测量的大脑活动表示不准确的方式影响 HDR 的时空特征。但是，在使用标准模型时，应注意识别可能无法提供大脑激活的准确表示的个体的 BOLD-fMRI 数据。不必为每个扫描会话检查 HDR，因为我们的数据表明中风幸存者的 HDR 特征在几天内是可重复的。
