title: Brain-state dependent uncoupling of BOLD and local field potentials in laminar olfactory bulb.
abstract: The neural activities of the olfactory bulb (OB) can be modulated significantly by internal brain states. While blood oxygenation level dependent functional MRI (BOLD-fMRI) has been extensively applied to study OB in small animals, the relationship between BOLD signals and electrophysiological signals remains to be elucidated. Our recent study has revealed a complex relationship between BOLD and local field potentials (LFP) signals in different OB layers during odor stimulation. However, no study has been performed to compare these two types of signals under global brain states. Here, the changes of BOLD and LFP signals in the glomerular, mitral cell, and granular cell layers of the OB under different brain states, which were induced by different concentrations of isoflurane, were sequentially acquired using electrode array and high-resolution MRI. It was found that under deeper anesthesia, the LFP powers in all layers were decreased but the BOLD signals were unexpectedly increased. Furthermore, the decreases of LFP powers were layer-independent, but the increases of BOLD signal were layer-specific, with the order of glomerular>mitral cell>granular cell layer. The results provide new evidence that the direct neural activity levels might not be correlated well with BOLD signals in some cases, and remind us that cautions should be taken to use BOLD signals as the index of neural activities.
authors: Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors: Ling
authors: L
authors: Gong
authors: Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors: Bo
authors: B
authors: Li
authors: Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors: Ruiqi
authors: R
authors: Wu
authors: Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China. Electronic address: aaliwipm@163.com.
authors: Anan
authors: A
authors: Li
authors: Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; Wuhan National Laboratory for Optoelectronics, Wuhan 430074, China. Electronic address: fuqiang.xu@wipm.ac.cn.
authors: Fuqiang
authors: F
authors: Xu
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000098:blood supply / Q000187:drug effects / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D007530:Isoflurane / Q000494:pharmacology; D008279:Magnetic Resonance Imaging; D010100:Oxygen / Q000097:blood*; D017207:Rats, Sprague-Dawley
chemical_list: D018685:Anesthetics, Inhalation; D002245:Carbon Dioxide; D007530:Isoflurane; D010100:Oxygen
keywords: Blood oxygenation level dependent (BOLD); Functional MRI; Layer-dependent; Local field potentials (LFP); Olfactory bulb