Towards an Improved Understanding of BOLD Signal Changes

描述(由申请人提供)：在电子记录中，尖锐的瞬变代表与单个神经元的动作电位相对应的神经活动的测量。这种尖峰活动反映了给定大脑区域的输出，但许多区域以兴奋性或抑制性突触电位的形式接受输入，而不产生尖峰。这种输入活动是计算积分的一种重要形式，在细胞外记录中被检测为局部场势(LFP)的扰动。LFP的定量分析是在频域进行的，提供了跨神经元同步活动的衡量标准。Logothetis等人。(2001)表明，BOLD可能以突触电位的形式反映一个区域的输入，而不是以棘波的形式反映其输出。突触输入可以是兴奋性的，也可以是抑制性的，这两种形式都涉及代谢需求，这可能会改变大胆和复杂的模型，将大胆解释为认知参与的代理。BOLD所反映的不同频段的振荡以及兴奋性和抑制性突触电位的时间进程，以及这些形式的活动和认知之间的关系，人们还知之甚少。因此，必须研究某些形式的神经活动、BOLD和认知过程的参与之间的对应关系。例如，在某些情况下，负面的大胆信号需要细致入微的解释。FMRI的减影性质最初表明，负性粗体只是反映了基线期间激活的增加。然而，许多研究结果表明，消极大胆代表着一种独特的现象。这项建议的重点是检验否定大胆反映与认知相关的神经活动减少的证据。将使用前面显示的任务执行BOLD和CBF的校准MR测量，以产生可靠的停用。这些流量和氧合的MR测量将被用来确定相对的CMRO2和氧提取，以全面评估BOLD的生理基础。将同时记录EEC，并将EEC功率在多个频段与MR测量进行比较。人们已经做了很多工作来表征要使用的任务中的EEC变化，但很少有人尝试将EEC与MR信号联系起来。这项工作将深入了解认知任务中MR信号的变化与表面和有限数量的患者硬膜下电极测量的EEC变化之间的关系。

DESCRIPTION (provided by applicant): Sharp transients, in electrical recordings, represent a measure of neural activity corresponding to an action potential at a single neuron. Such spike activity reflects the output of a given brain area, yet many regions receive input in the form of excitatory or inhibitory synaptic potentials without generating spikes. This input activity is an important form of computational integration, detected in extracellular recordings as perturbations of the local field potential (LFP). Quantitative analysis of the LFP is performed in the frequency domain, providing a measure of synchronous activity across neurons. Logothetis et al. (2001) showed that BOLD may reflect an area's input in the form of synaptic potentials, rather than its output in the form of spikes. Synaptic inputs can be excitatory or inhibitory, and both forms involve metabolic demands that may alter BOLD and complicate models interpreting BOLD as a proxy for cognitive engagement. The time- courses of oscillations in various frequency bands, and excitatory and inhibitory synaptic potentials, and the relationship between these forms of activity and cognition as reflected by BOLD, is poorly understood. Thus, it is essential to examine the correspondence between certain forms of neural activity, BOLD, and the engagement of cognitive processes. Negative BOLD signals in some cases, for example, demand a nuanced interpretation. The subtractive nature of fMRI initially suggests that negative BOLD simply reflects increased activation during the baseline. However, a number of findings have suggested that negative BOLD represents a distinct phenomenon. This proposal is focused on examining the evidence that negative BOLD reflects decreases in neural activity, associated with cognition. Calibrated MR measures of BOLD and CBF will be performed using tasks previously shown to produce reliable deactivations. These MR measures of flow and oxygenation will be used to determine relative CMRO2 and the oxygen extraction to fully assess the physiologic underpinnings of BOLD. Simultaneous EEC will be recorded and EEC power in multiple frequency bands compared with the MR measures. Much work has been performed characterizing EEC changes in the tasks to be used, but little work has attempted to relate EEC to MR signals. This work will provide insight into the relationship between MR signal changes in cognitive tasks, and EEC changes as measured with surface, and in a limited number of patients, subdural electrodes.