Measurements and modeling of the hemodynamic response function in human cerebral cortex

总结 短暂的神经活动会触发血管和代谢反应的混合， 刻板的动态这种血流动力学反应函数（HRF）在功能磁中得到了大量使用 共振成像（fMRI）。虽然HRF通常被假设为空间不变，但详细的测量结果 表明其动态表现出显着的时间变异性;这种变异性混淆了标准的线性 fMRI测量结果分析。尽管如此，变异性可能反映了血液之间不断变化的相互作用， 血流和氧代谢，可以提供关于大脑功能的非常有用的信息。因此， 强烈的兴趣，以更好地了解物理和生理学的HRF。 我们开发并验证了动脉冲动模型（AIM），该模型结合了新的流量描述， 隔室，一维，对流扩散氧运输。我们建议进一步开发和验证 该模型，再加上详细的调查的HRF。在实验上，我们使用多感官刺激 在整个大脑中广泛地唤起HRF的协议，并使用高分辨率动脉成像来评估反应。 自旋标记和功能磁共振成像来检查这些反应在大脑中的特征和变异性。我们将 扩展我们的模型，以更丰富的框架来解释这种HRF变异性的生物力学基础， 以前的模型，有可能将功能磁共振成像从粗略的神经相关转换为定量的神经相关。 脑血流量和代谢的测量。我们还将开发我们整体的临床应用- 脑HRF方法评估早期阿尔茨海默病（AD）或轻度认知障碍。我们的简单， 长达1小时功能磁共振成像评价具有提供AD病理学的前瞻性生物标志物的强大潜力。

Summary Brief periods of neural activity trigger a mixture of vascular and metabolic responses with somewhat stereotypical dynamics. This hemodynamic response function (HRF) is heavily used in functional magnetic resonance imaging (fMRI). While the HRF is usually assumed to be spatially invariant, detailed measurements show that its dynamics exhibit significant temporal variability; such variability confounds standard linear analysis of fMRI measurements. Nonetheless, the variability likely reflects changing interactions between blood flow and oxygen metabolism that could provide critically useful information about brain function. Thus, it is of strong interest to better understand the physics and physiology of the HRF. We developed and validated the Arterial Impulse Model (AIM) that combines a novel flow description with compartmental, 1D, convection-diffusion oxygen transport. We propose further development and validation of the model, coupled with detailed investigation of the HRF. Experimentally, we use multi-sensory stimulus protocols to evoke the HRF broadly across the brain, and evaluate the responses using high-resolution arterial spin labeling and fMRI to examine the character and variability of these responses across the brain. We will expand our model to explain the biomechanical basis of this HRF variability in a far richer framework than previous models, with the potential to transform fMRI from a rough neural correlate to a quantitative measurement of cerebral blood flow and metabolism. We will also develop a clinical application of our whole- brain HRF methods to evaluate early Alzheimer’s Disease (AD) or Mild Cognitive Impairment. Our simple, hour-long fMRI evaluation has strong potential to provide a prospective biomarker of AD pathology.