title: Physiological effects of a habituation procedure for functional MRI in awake mice using a cryogenic radiofrequency probe.
abstract: Functional magnetic resonance imaging (fMRI) in mice is typically performed under anesthesia due to difficulties in holding the head of awake mice stably with a conventional three-point fixation method that uses a tooth-bar and earplugs. Although some studies have succeeded in fMRI in awake mice by attaching a head-post on the skull, this cannot be applied to fMRI using a high signal-to-noise ratio (SNR) cryogenic MRI-detector, CryoProbe, because it covers the head of a mouse closely.
  
  
  
  We developed head-fixation implements for awake mice that are applicable to fMRI using CryoProbe.
  
  
  
  A head-bar was surgically attached to the skull of a mouse that was then habituated to a mock fMRI-environment, two hours/day for eight days with physiological examinations of body-weight, fecal weight, electromyogram (EMG), and electrocardiogram. EMG power decreased with just one day of habituation, whereas heart rate decreased after at least seven days of habituation. Estimated head motions of awake mice during fMRI were significantly smaller than a voxel size. Unexpectedly, temporal SNR of fMRI signals for awake mice was higher than that for anesthetized mice held by a conventional method. Functional connectivity in the brain of both anesthetized and awake mice showed bilateral and unilateral networks. COMPARISON WITH EXISTING METHOD(S): fMRI using CryoProbe had been performed on anesthetized mice previously. Our method does not use anesthetics during habituation or fMRI.
  
  
  
  Our method would be beneficial for translational research using fMRI in mice and humans because human fMRI is typically performed without anesthetics.
authors.affiliation: Department of Neuropsychiatry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Department of Neuropsychiatry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Mimura
authors.affiliation: Department of Physiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Ishihara
authors.affiliation: Department of Neuropsychiatry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nishida
authors.affiliation: Central Institute for Experimental Animals (CIEA), 3-25-12 Tonomachi, Kawasaki, Kanagawa 210-0821, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Komaki
authors.affiliation: Department of Neuropsychiatry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
authors.forename: Tomohito
authors.initials: T
authors.lastname: Minakuchi
authors.affiliation: NeuroSpin, Commissariat à l'Energie Atomique et aux Energies Alternatives, 91191 Gif-sur-Yvette, France.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Tsurugizawa
authors.affiliation: Department of Neuropsychiatry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Mimura
authors.affiliation: Department of Physiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Okano
authors.affiliation: Department of Neuropsychiatry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
authors.forename: Kenji F
authors.initials: KF
authors.lastname: Tanaka
authors.affiliation: Department of Neuropsychiatry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan; Central Institute for Experimental Animals (CIEA), 3-25-12 Tonomachi, Kawasaki, Kanagawa 210-0821, Japan. Electronic address: takata.norio@keio.jp.
authors.forename: Norio
authors.initials: N
authors.lastname: Takata
mesh_terms: D000758:Anesthesia; D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D001835:Body Weight / Q000502:physiology; D001921:Brain / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000502:physiology*; D004576:Electromyography; D007839:Functional Laterality; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000502:physiology; D010100:Oxygen / Q000097:blood; D011846:Radio Waves; D059629:Signal-To-Noise Ratio; D014851:Wakefulness
chemical_list: D000777:Anesthetics; D010100:Oxygen
keywords: Awake; Conscious; CryoProbe; Functional connectivity; Habituation; Mouse; Resting-state network; fMRI