title: Complex relationship between BOLD-fMRI and electrophysiological signals in different olfactory bulb layers.
abstract: Blood oxygenation level dependent functional magnetic resonance imaging (BOLD-fMRI), one of the most powerful technologies in neuroscience, measures neural activity indirectly. Therefore, systematic correlation of BOLD signals with other neural activity measurements is critical to understanding and then using the technology. Numerous studies have revealed that the BOLD signal is determined by many factors and is better correlated with local field potentials (LFP) than single/multiple unit firing. The relationship between BOLD and LFP signals under higher spatial resolution is complex and remains unclear. Here, changes of BOLD and LFP signals in the glomerular (GL), mitral cell (MCL), and granular cell layers (GCL) of the olfactory bulb were evoked by odor stimulation and sequentially acquired using high-resolution fMRI and electrode array. The experimental results revealed a rather complex relationship between BOLD and LFP signals. Both signal modalities were increased layer-dependently by odor stimulation, but the orders of signal intensity were significantly different: GL>MCL>GCL and GCL>GL>MCL for BOLD and LFP, respectively. During odor stimulation, the temporal features of LFPs were similar for a given band in different layers, but different for different frequency bands in a given layer. The BOLD and LFP signals in the low gamma frequency band correlated the best. This study provides new evidence for the consistency between structure and function in understanding the neurophysiological basis of BOLD signals, but also reminds that caution must be taken in interpreting of BOLD signals in regard to neural activity.
authors.affiliation: 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 the Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.affiliation: 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 the Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Gong
authors.affiliation: 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 the Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Ruiqi
authors.initials: R
authors.lastname: Wu
authors.affiliation: 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.forename: Anan
authors.initials: A
authors.lastname: Li
authors.affiliation: 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.forename: Fuqiang
authors.initials: F
authors.lastname: Xu
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001931:Brain Mapping / Q000379:methods*; D055724:Electrophysiological Phenomena; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging; D009830:Olfactory Bulb / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D010100:Oxygen
keywords: Blood oxygenation level dependent (BOLD); Functional MRI; Layer-dependent; Local field potentials (LFP); Olfactory bulb