title: Assessing sensory versus optogenetic network activation by combining (o)fMRI with optical Ca2+ recordings.
abstract: Encoding of sensory inputs in the cortex is characterized by sparse neuronal network activation. Optogenetic stimulation has previously been combined with fMRI (ofMRI) to probe functional networks. However, for a quantitative optogenetic probing of sensory-driven sparse network activation, the level of similarity between sensory and optogenetic network activation needs to be explored. Here, we complement ofMRI with optic fiber-based population Ca2+recordings for a region-specific readout of neuronal spiking activity in rat brain. Comparing Ca2+responses to the blood oxygenation level-dependent signal upon sensory stimulation with increasing frequencies showed adaptation of Ca2+transients contrasted by an increase of blood oxygenation level-dependent responses, indicating that the optical recordings convey complementary information on neuronal network activity to the corresponding hemodynamic response. To study the similarity of optogenetic and sensory activation, we quantified the density of cells expressing channelrhodopsin-2 and modeled light propagation in the tissue. We estimated the effectively illuminated volume and numbers of optogenetically stimulated neurons, being indicative of sparse activation. At the functional level, upon either sensory or optogenetic stimulation we detected single-peak short-latency primary Ca2+responses with similar amplitudes and found that blood oxygenation level-dependent responses showed similar time courses. These data suggest that ofMRI can serve as a representative model for functional brain mapping.
authors.affiliation: Department of Clinical Radiology, University Hospital Münster, Münster, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Schmid
authors.affiliation: Department of Clinical Radiology, University Hospital Münster, Münster, Germany.
authors.forename: Lydia
authors.initials: L
authors.lastname: Wachsmuth
authors.affiliation: Focus Program translational Neuroscience & Institute for Microscopic Anatomy and Neurobiology, Johannes Gutenberg-University Mainz, Mainz, Germany.
authors.forename: Miriam
authors.initials: M
authors.lastname: Schwalm
authors.affiliation: Focus Program translational Neuroscience & Institute for Microscopic Anatomy and Neurobiology, Johannes Gutenberg-University Mainz, Mainz, Germany.
authors.forename: Pierre-Hugues
authors.initials: PH
authors.lastname: Prouvot
authors.affiliation: Focus Program translational Neuroscience & Institute for Microscopic Anatomy and Neurobiology, Johannes Gutenberg-University Mainz, Mainz, Germany.|Faculty of Psychology, Diego Portales University, Santiago, Chile.
authors.forename: Eduardo Rosales
authors.initials: ER
authors.lastname: Jubal
authors.affiliation: Focus Program translational Neuroscience & Institute for Microscopic Anatomy and Neurobiology, Johannes Gutenberg-University Mainz, Mainz, Germany.
authors.forename: Consuelo
authors.initials: C
authors.lastname: Fois
authors.affiliation: Focus Program translational Neuroscience & Institute for Microscopic Anatomy and Neurobiology, Johannes Gutenberg-University Mainz, Mainz, Germany.
authors.forename: Gautam
authors.initials: G
authors.lastname: Pramanik
authors.affiliation: Department of Neuroradiology, Technical University Munich, Munich, Germany.
authors.forename: Claus
authors.initials: C
authors.lastname: Zimmer
authors.affiliation: Department of Clinical Radiology, University Hospital Münster, Münster, Germany faberc@uni-muenster.de.
authors.forename: Cornelius
authors.initials: C
authors.lastname: Faber
authors.affiliation: Focus Program translational Neuroscience & Institute for Microscopic Anatomy and Neurobiology, Johannes Gutenberg-University Mainz, Mainz, Germany.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Stroh
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000075402:Channelrhodopsins; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D005452:Fluoresceins / Q000737:chemistry; D005822:Genetic Vectors; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000378:metabolism*; D055100:Optical Fibers; D062308:Optogenetics / Q000379:methods*; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D011916:Rats, Inbred F344; D013003:Somatosensory Cortex / Q000000981:diagnostic imaging* / Q000378:metabolism; D014161:Transduction, Genetic
chemical_list: D000814:Aniline Compounds; D000075402:Channelrhodopsins; D005452:Fluoresceins; C503942:Oregon green 488 BAPTA-1; D010100:Oxygen; D002118:Calcium
keywords: Optogenetic fMRI; calcium recordings; light propagation; optical neurophysiology; sparse network activation