title: Adaptive motion processing in bilateral vestibular failure.
abstract: BACKGROUND
  Patients with bilateral vestibular failure (BVF) suffer from oscillopsia during head movements. This is secondary to the loss of the vestibulo-ocular reflex which is responsible for stabilising retinal images during head movements of high frequency or velocity. Previous studies documented decreased visual motion sensitivity in such patients at low velocities. The authors now examine motion coherence tasks, which have two advantages: (1) the task is associated with the functions of the middle temporal area; and (2) it affords testing at low and high motion velocities, as relevant for patients with oscillopsia due to BVF.
  
  
  METHODS
  Nine BVF patients and nine healthy control subjects were examined with a random dot pattern with variable percentages of dots moving in the target direction. Participants were asked to indicate in which of two possible directions they perceived the coherent motion. Horizontal and vertical planes were tested at speeds from 0.156 to 40°/s.
  
  
  RESULTS
  Motion coherence thresholds were lower at higher speeds in both groups (p<0.0001). BVF patients had raised motion coherence thresholds (p=0.002) across all velocities as compared with the control subject group.
  
  
  CONCLUSIONS
  In a motion coherence paradigm, BVF patients show raised thresholds. This is the first demonstration of diminished visual motion processing at high velocities, supporting the view that the changes allow BVF patients to partly compensate for the oscillopsia. The findings are interpreted as an adaptive process likely to involve the middle temporal visual motion processing areas.
authors.affiliation: Department of Neurology and IFBLMU, University of Munich Hospital, Munich, Germany.
authors.forename: Roger
authors.initials: R
authors.lastname: Kalla
authors.forename: Neil
authors.initials: N
authors.lastname: Muggleton
authors.forename: Rainer
authors.initials: R
authors.lastname: Spiegel
authors.forename: Domenica
authors.initials: D
authors.lastname: Bueti
authors.forename: Jens
authors.initials: J
authors.lastname: Claassen
authors.forename: Vincent
authors.initials: V
authors.lastname: Walsh
authors.forename: Adolfo
authors.initials: A
authors.lastname: Bronstein
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D005260:Female; D019416:Head Movements; D006801:Humans; D008297:Male; D008875:Middle Aged; D009038:Motion; D009039:Motion Perception; D009068:Movement; D010468:Perceptual Disorders / Q000175:diagnosis*; D012984:Software; D015837:Vestibular Diseases / Q000175:diagnosis*