title: Why use a mirror to assess visual pursuit in prolonged disorders of consciousness? Evidence from healthy control participants.
abstract: BACKGROUND
  Evidence of reliable smooth visual pursuit is crucial for both diagnosis and prognosis in prolonged disorders of consciousness (PDOC). However, a mirror is more likely than an object to elicit evidence of smooth pursuit. Our objective was to identify the physiological and/or cognitive mechanism underlying the mirror benefit.
  
  
  METHODS
  We recorded eye-movements while healthy participants simultaneously completed a visual pursuit task and a cognitively demanding two-back task. We manipulated the stimulus to be pursued (two levels: mirror, ball) and the simultaneous cognitive load (pursuit only, pursuit plus two-back task) within subjects.
  
  
  RESULTS
  Pursuit of the reflected-own-face in the mirror was associated with briefer fixations that occurred less uniformly across the horizontal plane relative to object pursuit. Secondary task performance did not differ between pursuit stimuli. The secondary task also did not affect eye movement measures, nor did it interact with pursuit stimulus.
  
  
  CONCLUSIONS
  Reflected-own-face pursuit is no less cognitively demanding than object pursuit, but it naturally elicits smoother eye movements (i.e. briefer pauses to fixate). A mirror therefore provides greater sensitivity to detect smooth visual pursuit in PDOC because the naturally smoother eye movements may be identified more confidently by the assessor.
authors.affiliation: School of Psychology, University of Birmingham, Birmingham, B15 2TT, England. d.cruse@bham.ac.uk.
authors.forename: Damian
authors.initials: D
authors.lastname: Cruse
authors.affiliation: Department of Neurorehabilitation, University Hospital of Ghent, Ghent, 9000, Belgium.
authors.forename: Marco
authors.initials: M
authors.lastname: Fattizzo
authors.affiliation: The Brain and Mind Institute, University of Western Ontario, London, Ontario, N6A 5B7, Canada.
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Owen
authors.affiliation: School of Psychology, University of Birmingham, Birmingham, B15 2TT, England.
authors.forename: Davinia
authors.initials: D
authors.lastname: Fernández-Espejo
mesh_terms: D000328:Adult; D003244:Consciousness Disorders / Q000175:diagnosis*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009460:Neurologic Examination / Q000379:methods*; D011698:Pursuit, Smooth / Q000502:physiology*; D055815:Young Adult
keywords: Brain injuries; Consciousness disorders; Diagnosis; Smooth pursuit