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

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。许多研究试图从血氧水平依赖性（BOLD）反应的幅度和时间特征的测量中得出关于各种认知功能的定量推断。然而，BOLD对比并不是代谢的直接测量，而是局部血流变化和伴随的氧合变化的结果。因此，增加的神经元放电引起级联反应，最终导致血流上调的血管舒缩反应，即代谢增加引起局部的、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，也是血管反应性的特征。正因为如此，为了提高认知推断的特异性以及提高群体测量的敏感性，去除特定于受试者或疗程内血流动力学反应的变异将是谨慎的。整体高碳酸血症被认为是不同受试者、不同脑区和扫描环境特征（采集参数、场强等）之间神经反应的正常化因素。预期BH可以用于BOLD反应的标准化或校准，因为BH诱导的BOLD反应具有区域特异性，并且与BOLD测量的神经反应成正比。本研究使用BOLD效应测量对最低认知，高碳酸血症挑战的反应，即屏气任务，应用于工作记忆（WM）认知任务的纠正。为了减少受试者之间的方差，同时在我们的全局校正中保留区域特异性，在个体素的基础上对受试者进行校正。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