title: The effects of neck flexion on cerebral potentials evoked by visual, auditory and somatosensory stimuli and focal brain blood flow in related sensory cortices.
abstract: BACKGROUND
  A flexed neck posture leads to non-specific activation of the brain. Sensory evoked cerebral potentials and focal brain blood flow have been used to evaluate the activation of the sensory cortex. We investigated the effects of a flexed neck posture on the cerebral potentials evoked by visual, auditory and somatosensory stimuli and focal brain blood flow in the related sensory cortices.
  
  
  METHODS
  Twelve healthy young adults received right visual hemi-field, binaural auditory and left median nerve stimuli while sitting with the neck in a resting and flexed (20° flexion) position. Sensory evoked potentials were recorded from the right occipital region, Cz in accordance with the international 10-20 system, and 2 cm posterior from C4, during visual, auditory and somatosensory stimulations. The oxidative-hemoglobin concentration was measured in the respective sensory cortex using near-infrared spectroscopy.
  
  
  RESULTS
  Latencies of the late component of all sensory evoked potentials significantly shortened, and the amplitude of auditory evoked potentials increased when the neck was in a flexed position. Oxidative-hemoglobin concentrations in the left and right visual cortices were higher during visual stimulation in the flexed neck position. The left visual cortex is responsible for receiving the visual information. In addition, oxidative-hemoglobin concentrations in the bilateral auditory cortex during auditory stimulation, and in the right somatosensory cortex during somatosensory stimulation, were higher in the flexed neck position.
  
  
  CONCLUSIONS
  Visual, auditory and somatosensory pathways were activated by neck flexion. The sensory cortices were selectively activated, reflecting the modalities in sensory projection to the cerebral cortex and inter-hemispheric connections.
authors.affiliation: Department of Human Movement and Health, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan. fujikatu@med.m.kanazawa-u.ac.jp
authors.forename: Katsuo
authors.initials: K
authors.lastname: Fujiwara
authors.forename: Kenji
authors.initials: K
authors.lastname: Kunita
authors.forename: Naoe
authors.initials: N
authors.lastname: Kiyota
authors.forename: Aida
authors.initials: A
authors.lastname: Mammadova
authors.forename: Mariko
authors.initials: M
authors.lastname: Irei
mesh_terms: D000328:Adult; D002560:Cerebrovascular Circulation / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008297:Male; D009333:Neck; D011187:Posture / Q000502:physiology*; D013003:Somatosensory Cortex / Q000098:blood supply* / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared; D018709:Statistics, Nonparametric; D014793:Visual Cortex / Q000098:blood supply* / Q000502:physiology*
chemical_list: D006454:Hemoglobins