Contribution of Ultra Low Frequency LFPs to Functional MRI

描述（由申请人提供）：静息状态MRI （rsMRI）基于血氧水平依赖（BOLD）信号的波动，越来越多地用于绘制大脑自发活动网络。这些波动的神经基础尚不清楚，各种研究报告与低频功率、高频功率、尖峰调制和血管舒缩有关。虽然BOLD波动的频率范围为0-0.1 Hz，但以前的研究已经检查了更高频段（> - 1hz）的电活动。然而，众所周知，大脑中存在次慢振荡（ifso; < 1hz），并且它们与正常受试者和ADHD患者的注意力控制和反应时间波动有关。我们假设BOLD波动与同一频段的电波动有直接联系，并且这些较慢的振荡对较高频率的调制导致与BOLD信号的状态依赖关系。1. 确定次慢电位波动与典型LFP波段（1-100 Hz）活动之间的关系。ifso和宽带局部场电位（lfp）将从皮层和皮层下的网络中记录下来，以确定ifso的空间分布以及它们如何影响局部活动。同时IFSO和细胞内记录将检查膜电位变化是否与低频振荡有关。不同的麻醉状态会发生调节

DESCRIPTION (provided by applicant): Resting state MRI (rsMRI), based on fluctuations in the blood oxygenation level dependent (BOLD) signal, is increasingly used to map networks of spontaneous activity in the brain. The neural basis of these fluctuations is not well understood, with various studies reporting a link to low frequency power, high frequency power, modulation of spiking, and vasomotion. While the frequency range of the BOLD fluctuations is 0-0.1 Hz, previous studies have examined electrical activity in higher frequency bands (>1 Hz). It is known, however, that infra-slow oscillations (IFSOs; <1 Hz) exist in the brain and they have been linked to fluctuations in attentional control and reaction time in normal subjects and ADHD patients. We hypothesize that the BOLD fluctuations have a direct link to electrical fluctuations in the same frequency band, and that the modulation of higher frequencies by these slower oscillations leads to state-dependent relationships with the BOLD signal. 1. Determine the relationship between infra-slow potential fluctuations and activity in typical LFP bands (1-100 Hz). IFSOs and broadband local field potentials (LFPs) will be recorded from a network of cortical and subcortical sites to determine the spatial distribution of IFSOs and how they affect local activity. Simultaneous IFSO and intracellular recording will examine whether membrane potential changes are tied to low frequency oscillations. Different anesthetic states will modulate neural activity. 2. Characterize the contribution of IFSOs to the BOLD signal on a site-by-site and network basis. No studies have looked at the direct frequency correlates of the low frequency BOLD fluctuations. Preliminary data suggests that patterns of IFSOs can be mapped using MRI. Using a simultaneous recording/imaging protocol developed in our lab, we will obtain LFPs (broadband and infra-slow) and BOLD from sites selected from the network examined in aim 1. Correlation between LFPs and local BOLD signal will be performed to determine the largest contribution to BOLD fluctuations, while coherence between band-limited LFPs and BOLD correlation will be compared to identify the best predictors of BOLD correlation. 3. Examine the spatiotemporal dynamics of IFSOs and determine their link to quasi-periodic BOLD fluctuations. Preliminary data indicates that the time-lagged correlation between BOLD and IFSOs demonstrates a pattern of propagation along the cortex that is highly similar to the spatiotemporal dynamics previously observed with the BOLD signal. This aim will directly examine the link between BOLD and IFSO dynamics using the simultaneously-acquired multi-site data collected for aims 1 and 2. This project will provide unique insight into the network activity that underlies functional connectivity maps created with MRI and, if our hypothesis proves correct, will lead to a new way to map the spatiotemporal patterns of the infra-slow activity that modulates attention throughout the whole brain with resolution unobtainable with electroencephalography. PUBLIC HEALTH RELEVANCE: The goal of this project is to determine how very low frequency electrical activity modulates other activity in the brain, and how this in turn relates t the functional MRI signal. An improved understanding of spontaneous MRI signal fluctuations is the first step toward our long-term goal of establishing resting state MRI as a noninvasive tool for the diagnosis and evaluation of clinical disorders.