Hemodynamic response function in patients with stroke-induced aphasia: Implications for fMRI data analysis
Hemodynamic response function in patients with stroke-induced aphasia: Implications for fMRI data analysis
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DOI：
10.1016/j.neuroimage.2007.02.035
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发表时间：
2007-06-01
期刊：
影响因子：
5.7
通讯作者：
Thompson, C. K.
中科院分区：
文献类型：
--
作者：
Bonakdarpour, B.;Parrish, T. B.;Thompson, C. K.
功能性MRI是基于神经元氧化代谢增加引发的脑微血管变化。血流的这种变化遵循称为血液动力学响应函数（HRF）的模式，其通常在刺激递送后4-6秒达到峰值。然而，在脑血管疾病的存在下，HRF可能不遵循这种正常模式，由于时间信噪比（tSNR）或延迟的HRF，这可能会导致误解或低估的fMRI信号。本研究采用词汇判断任务和长时间事件相关试验设计，检测了5名中风失语患者和4名正常人的HRF和SNR。使用MP-MRI序列采集T1加权图像，使用回波平面成像采集BOLD T2* 加权图像，以测量HRF中的达峰时间（TTP）。使用Brain Voyager分析了已知参与语言处理的四个解剖区域的数据：Broca区和后外侧裂周网络（PPN）（包括Wernicke区，角回和缘上回）以及这些区域的右半球同源物。还检查了枕区作为对照区域。分析表明，在5名患者中，有3名患者的左侧外侧裂周区的TTP与正常人和相同患者的左侧初级视皮层相比显著增加。在另外两名患者中，未发现明显的延迟。我们还发现，BOLD信号检测的信噪比可能会不足，在损坏的区域。这些研究结果表明，获得生理（TTP）和质量保证（tSNR）的信息是必不可少的研究激活模式在脑损伤患者，以避免错误的数据解释。一个这样的误解和需要替代数据分析策略的例子进行了讨论。(c)2007爱思唯尔公司All rights reserved.
Functional MRI is based on changes in cerebral microvasculature triggered by increased neuronal oxidative metabolism. This change in blood flow follows a pattern known as the hemodynamic response function (HRF), which typically peaks 4-6 s following stimulus delivery. However, in the presence of cerebrovascular disease the HRF may not follow this normal pattern, due to either the temporal signal to noise (tSNR) ratio or delays in the HRF, which may result in misinterpretation or underestimation of fMRI signal. The present study examined the HRF and SNR in five individuals with aphasia resulting from stroke and four unimpaired participants using a lexical decision task and a long trial event-related design. T1-weighted images were acquired using an MP-RAGE sequence and BOLD T2*-weighted images were acquired using Echo Planar Imaging to measure time to peak (TTP) in the HRF. Data were analyzed using Brain Voyager in four anatomic regions known to be involved in language processing: Broca's area and the posterior perisylvian network (PPN) (including Wernicke's area, the angular and supramarginal gyri) and right hemisphere homologues of these regions. The occipital area also was examined as a control region. Analyses showed that the TTP in three out of five patients in the left perisylvian area was increased significantly as compared to normal individuals and the left primary visual cortex in the same patients. In two other patients no significant delays were detected. We also found that the SNR for BOLD signal detection may by insufficient in damaged areas. These findings indicate that obtaining physiologic (TTP) and quality assurance (tSNR) information is essential for studying activation patterns in brain-damaged patients in order to avoid errors in interpretation of the data. An example of one such misinterpretation and the need for alternative data analysis strategies is discussed. (c) 2007 Elsevier Inc. All rights reserved.