title: Functional imaging of olfaction by CBV fMRI in monkeys: insight into the role of olfactory bulb in habituation.
abstract: Cerebral blood volume (CBV) fMRI with superparamagnetic iron oxide nanoparticles (USPIO) as contrast agent was used to investigate the odorant-induced olfaction in anesthetized rhesus monkeys. fMRI data were acquired in 24 axial slices covering the entire brain, with isoamyl-acetate as the odor stimulant. For each experiment, multiple fMRI measurements were made during a 1- or 2-h period, with each measurement consisting of a baseline period, a stimulation period, and a recovery period. Three different stimulation paradigms with a stimulation period of 1 min, 2 min, or 8 min, respectively, were used to study the olfactory responses in the olfactory bulb (OB). Odorant-induced CBV increases were observed in the OB of each individual monkey. The spatial and temporal activation patterns were reproducible within and between animals. The sensitivity of CBV fMRI in OB was comparable with the sensitivities reported in previous animal fMRI studies. The CBV responses during the 1-min, 2-min, or 8-min odor stimulation period were relatively stable, and did not show attenuation. The amplitudes of CBV response to the repeated stimuli during the 1- or 2-h period were also stable. The stable CBV response in the OB to both continuous and repeated odor stimuli suggests that the OB may not play a major role in olfactory habituation. The technical approach described in this report can enable more extensive fMRI studies of olfactory processing in OB of both humans and non-human primates.
authors.affiliation: Merck research labs, West Point, PA 19486, USA. Electronic address: fuqiang_zhao@merck.com.
authors.forename: Fuqiang
authors.initials: F
authors.lastname: Zhao
authors.affiliation: Merck research labs, West Point, PA 19486, USA.
authors.forename: Marie A
authors.initials: MA
authors.lastname: Holahan
authors.affiliation: Merck research labs, West Point, PA 19486, USA.
authors.forename: Andrea K
authors.initials: AK
authors.lastname: Houghton
authors.affiliation: Merck research labs, West Point, PA 19486, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Hargreaves
authors.affiliation: Merck research labs, West Point, PA 19486, USA.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Evelhoch
authors.affiliation: Merck research labs, West Point, PA 19486, USA.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Winkelmann
authors.affiliation: Merck research labs, West Point, PA 19486, USA.
authors.forename: Donald S
authors.initials: DS
authors.lastname: Williams
mesh_terms: D000818:Animals; D001810:Blood Volume / Q000502:physiology; D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology; D003287:Contrast Media; D005260:Female; D005290:Ferric Compounds; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging / Q000379:methods*; D053758:Nanoparticles; D009812:Odorants; D009830:Olfactory Bulb / Q000098:blood supply / Q000502:physiology*; D055696:Olfactory Perception / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D012903:Smell / Q000502:physiology*
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; C000499:ferric oxide; D010100:Oxygen
keywords: Dexmedetomidine; Habituation; Monkey; Olfactory; USPIO; fMRI