title: Visual exploration during locomotion limited by fear of heights.
abstract: BACKGROUND
  Visual exploration of the surroundings during locomotion at heights has not yet been investigated in subjects suffering from fear of heights.
  
  
  METHODS
  Eye and head movements were recorded separately in 16 subjects susceptible to fear of heights and in 16 non-susceptible controls while walking on an emergency escape balcony 20 meters above ground level. Participants wore mobile infrared eye-tracking goggles with a head-fixed scene camera and integrated 6-degrees-of-freedom inertial sensors for recording head movements. Video recordings of the subjects were simultaneously made to correlate gaze and gait behavior.
  
  
  RESULTS
  Susceptibles exhibited a limited visual exploration of the surroundings, particularly the depth. Head movements were significantly reduced in all three planes (yaw, pitch, and roll) with less vertical head oscillations, whereas total eye movements (saccade amplitudes, frequencies, fixation durations) did not differ from those of controls. However, there was an anisotropy, with a preference for the vertical as opposed to the horizontal direction of saccades. Comparison of eye and head movement histograms and the resulting gaze-in-space revealed a smaller total area of visual exploration, which was mainly directed straight ahead and covered vertically an area from the horizon to the ground in front of the feet. This gaze behavior was associated with a slow, cautious gait.
  
  
  CONCLUSIONS
  The visual exploration of the surroundings by susceptibles to fear of heights differs during locomotion at heights from the earlier investigated behavior of standing still and looking from a balcony. During locomotion, anisotropy of gaze-in-space shows a preference for the vertical as opposed to the horizontal direction during stance. Avoiding looking into the abyss may reduce anxiety in both conditions; exploration of the "vertical strip" in the heading direction is beneficial for visual control of balance and avoidance of obstacles during locomotion.
authors.affiliation: Institute of Clinical Neurosciences, University of Munich, Munich, Germany; German Center for Vertigo and Balance Disorders, University of Munich, Munich, Germany.
authors.forename: Günter
authors.initials: G
authors.lastname: Kugler
authors.affiliation: Institute of Clinical Neurosciences, University of Munich, Munich, Germany; German Center for Vertigo and Balance Disorders, University of Munich, Munich, Germany.
authors.forename: Doreen
authors.initials: D
authors.lastname: Huppert
authors.affiliation: Institute of Clinical Neurosciences, University of Munich, Munich, Germany; German Center for Vertigo and Balance Disorders, University of Munich, Munich, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Eckl
authors.affiliation: Institute of Clinical Neurosciences, University of Munich, Munich, Germany; German Center for Vertigo and Balance Disorders, University of Munich, Munich, Germany; Brandenburg University of Technology Cottbus - Senftenberg, Senftenberg, Germany.
authors.forename: Erich
authors.initials: E
authors.lastname: Schneider
authors.affiliation: Institute of Clinical Neurosciences, University of Munich, Munich, Germany; German Center for Vertigo and Balance Disorders, University of Munich, Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Brandt
mesh_terms: D000328:Adult; D000368:Aged; D016880:Anisotropy; D005133:Eye Movements; D005260:Female; D005684:Gait; D019416:Head Movements; D006801:Humans; D008297:Male; D008875:Middle Aged; D009949:Orientation; D010698:Phobic Disorders / Q000503:physiopathology*; D065855:Spatial Processing