title: Direct detection of optogenetically evoked oscillatory neuronal electrical activity in rats using SLOE sequence.
abstract: The direct detection of neuronal electrical activity is one of the most challenging goals in non-BOLD fMRI research. Previous work has demonstrated its feasibility in phantom and cell culture studies, but attempts in in vivo studies remain few and far between. Most recent in vivo studies used T2*-weighted sequences to directly detect neuronal electrical activity evoked by sensory stimulus. As neuronal electrical signal is usually comprised of a series of spectrally distributed oscillatory waveforms rather than being a direct current, it is most likely to be detected using oscillatory current sensitive sequences. In this study, we explored the potential of using the spin-lock oscillatory excitation (SLOE) sequence with spiral readout to directly detect optogenetically evoked oscillatory neuronal electrical activity, whose main spectral component can be manipulated artificially to match the resonance frequency of spin-lock RF field. In addition, experiments using the stimulus-induced rotary saturation (SIRS) sequence with spiral readout were also performed. Electrophysiological recording and MRI data acquisition were conducted on separate animals. Robust optogenetically evoked oscillatory LFP signals were observed and significant BOLD signals were acquired with the GE-EPI sequence before and after the whole SLOE and SIRS acquisitions, but no significant neuronal current MRI (ncMRI) signal changes were detected. These results indicate that the sensitivity of oscillatory current sensitive sequences needs to be further improved for direct detection of neuronal electrical activity.
authors.affiliation: Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, People's Republic of China; Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, People's Republic of China.
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Chai
authors.affiliation: School of Life Sciences, University of Science and Technology of China, Hefei, People's Republic of China.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Bi
authors.affiliation: Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, People's Republic of China.
authors.forename: Liping
authors.initials: L
authors.lastname: Wang
authors.affiliation: Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, People's Republic of China; CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, People's Republic of China.
authors.forename: Fuqiang
authors.initials: F
authors.lastname: Xu
authors.affiliation: Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, People's Republic of China; CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, People's Republic of China.
authors.forename: Ruiqi
authors.initials: R
authors.lastname: Wu
authors.affiliation: Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: School of Information Science and Technology, University of Science and Technology of China, Hefei, People's Republic of China.
authors.forename: Bensheng
authors.initials: B
authors.lastname: Qiu
authors.affiliation: Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, People's Republic of China.
authors.forename: Hao
authors.initials: H
authors.lastname: Lei
authors.affiliation: Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, People's Republic of China; Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, People's Republic of China.
authors.forename: Yaoyu
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, People's Republic of China; Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, People's Republic of China; McGovern Institute for Brain Research, Peking University, Beijing, People's Republic of China. Electronic address: jgao@pku.edu.cn.
authors.forename: Jia-Hong
authors.initials: JH
authors.lastname: Gao
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009474:Neurons / Q000502:physiology*; D062308:Optogenetics; D019047:Phantoms, Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley
keywords: Functional MRI; Neuronal current; Neuronal electrical activity; Optogenetics; Oscillatory current; Spin-lock