title: The neural cascade of olfactory processing: a combined fMRI-EEG study.
abstract: Olfaction is dependent on respiration for the delivery of odorants to the nasal cavity. Taking advantage of the time-locked nature of inspiration and olfactory processing, electroencephalogram dipole modeling (EEG/DT) has previously been used to identify a cascade of inspiration-triggered neural activity moving from primary limbic olfactory regions to frontal cortical areas during odor perception. In this study, we leverage the spatial resolution of functional magnetic resonance imaging (fMRI) alongside the temporal resolution of EEG to replicate and extend these findings. Brain activation identified by both modalities converged within association regions of the orbitofrontal cortex that were activated from approximately 150-300 ms after inspiration onset. EEG/DT was additionally sensitive to more transient activity in primary olfactory regions, including the parahippocampal gyrus and amygdala, occurring approximately 50 ms post-inspiration. These results provide a partial validation of the spatial profile of the olfactory cascade identified by EEG source modeling, and inform novel future directions in the investigation of human olfaction.
authors: Department of Physiology, Showa University School of Medicine, Tokyo, Japan; Melbourne Neuropsychiatry Centre, Department of Psychiatry, University of Melbourne and Melbourne Health, Melbourne, VIC, Australia. Electronic address: faustus@med.showa-u.ac.jp.
authors: Yuri
authors: Y
authors: Masaoka
authors: Melbourne Neuropsychiatry Centre, Department of Psychiatry, University of Melbourne and Melbourne Health, Melbourne, VIC, Australia.
authors: Ian H
authors: IH
authors: Harding
authors: Human Arts and Sciences Research Center, University of Human Arts and Sciences, Saitama, Japan.
authors: Nobuyoshi
authors: N
authors: Koiwa
authors: Department of Ophthalmology, Jikei Medical University, Tokyo, Japan.
authors: Masaki
authors: M
authors: Yoshida
authors: Melbourne Neuropsychiatry Centre, Department of Psychiatry, University of Melbourne and Melbourne Health, Melbourne, VIC, Australia.
authors: Ben J
authors: BJ
authors: Harrison
authors: Melbourne Neuropsychiatry Centre, Department of Psychiatry, University of Melbourne and Melbourne Health, Melbourne, VIC, Australia; Monash Clinical & Imaging Neuroscience, School of Psychological Sciences and Monash Biomedical Imaging, Monash University, Melbourne, VIC, Australia.
authors: Valentina
authors: V
authors: Lorenzetti
authors: Department of Radiology, Stroke Center, Ebara Tokyo Hospital, Tokyo, Japan.
authors: Masahiro
authors: M
authors: Ida
authors: Department of Physiology, Showa University School of Medicine, Tokyo, Japan.
authors: Masahiko
authors: M
authors: Izumizaki
authors: Melbourne Neuropsychiatry Centre, Department of Psychiatry, University of Melbourne and Melbourne Health, Melbourne, VIC, Australia.
authors: Christos
authors: C
authors: Pantelis
authors: Tokyo Ariake University of Medical and Health Sciences, Tokyo, Japan.
authors: Ikuo
authors: I
authors: Homma
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D064847:Multimodal Imaging; D009812:Odorants; D055696:Olfactory Perception / Q000502:physiology*; D010812:Physical Stimulation; D012119:Respiration
keywords: Amygdala; Electroencephalogram; Inspiration; Olfaction; Piriform; fMRI