BOLD FMRI RESPONSE IS AN INDIRECT CONSEQUENCE OF CHANGES IN NEURONAL METABOLISM

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。许多研究试图通过测量血氧水平依赖(BOLD)反应的幅度和时间特征来对各种认知功能做出定量推断。然而，这种大胆的对比并不是新陈代谢的直接测量，而是局部血流变化和伴随的氧合变化的结果。因此，神经元放电的增加引起一系列的级联反应，最终导致血管运动反应，其中血流量被上调，即代谢增加导致局部的任务激活启动的血流动力学反应，这不仅是神经活动的特征，也是血管反应的特征。正因为如此，为了提高认知推论的特异性以及提高群体测量的敏感性，谨慎的做法是去除受试者内或会话内血流动力学反应特有的变异。全局性高碳酸血症已被建议用于正常化不同受试者、不同脑区和扫描环境特征(获取参数、场强等)之间的神经反应。预计BH可用于正常化或BOLD反应的校准，因为BH诱导的BOLD反应具有地区性特异性，并与BOLD测量的神经反应成比例。本研究使用对低认知、高碳酸血症挑战(即屏息任务)所测量的大胆效应对工作记忆(WM)认知任务进行校正。为了减少受试者之间的差异，同时在我们的全局校正中保持区域特异性，在受试者内部逐个体素地进行了校正。我们期望这种形式的血流动力学反应校正将为组间和纵向研究以及多中心研究提供重要贡献。

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. Many studies seek to draw quantitative inferences about various cognitive functions from measurements of the amplitude and temporal characteristics of the blood-oxygen level dependent (BOLD) response. However, the BOLD contrast is not a direct measure of metabolism but rather results from changes in regional blood flow and attendant alterations in oxygenation.. Thus, increased neuronal firing causes a cascade that culminates in a vasomotor reaction wherein blood flow is upregulated, i.e. metabolic increases cause a local, task-activation-initiated hemodynamic response that is characteristic not only of the neural activity but also the vascular reactivity. Because of this, it would be prudent to remove variations specific to within-subject or within-session hemodynamic response in order to improve specificity of cognitive inferences as well as to improve sensitivity of group measures. Global hypercapnia has been suggested for normalizing neural response between different subjects, different brain regions, and features of the scanning environment (acquisition parameters, field strength, etc. It is expected that BH can be used for normalization, or calibration of BOLD responsiveness, because BH-induced BOLD response is regionally specific and proportional to neural responses measured by BOLD. The present study uses BOLD effect measured in response to a minimally cognitive, hypercapnic challenge, i.e. a breath-holding task, to apply correction to a working memory (WM) cognitive task. The correction was performed within subjects on a voxel by voxel basis in order to reduce variance across subjects, while retaining regional specificity within our global correction. We expect that this form of hemodynamic response correction will provide an important contribution for between-group and longitudinal studies as well as for multi-center studies