title: Quick phases of infantile nystagmus show the saccadic inhibition effect.
abstract: OBJECTIVE
  Infantile nystagmus (IN) is a pathological, involuntary oscillation of the eyes consisting of slow, drifting eye movements interspersed with rapid reorienting quick phases. The extent to which quick phases of IN are programmed similarly to saccadic eye movements remains unknown. We investigated whether IN quick phases exhibit 'saccadic inhibition,' a phenomenon typically related to normal targeting saccades, in which the initiation of the eye movement is systematically delayed by task-irrelevant visual distractors.
  
  
  METHODS
  We recorded eye position from 10 observers with early-onset idiopathic nystagmus while task-irrelevant distractor stimuli were flashed along the top and bottom of a large screen at ±10° eccentricity. The latency distributions of quick phases were measured with respect to these distractor flashes. Two additional participants, one with possible albinism and one with fusion maldevelopment nystagmus syndrome, were also tested.
  
  
  RESULTS
  All observers showed that a distractor flash delayed the execution of quick phases that would otherwise have occurred approximately 100 ms later, exactly as in the standard saccadic inhibition effect. The delay did not appear to differ between the two main nystagmus types under investigation (idiopathic IN with unidirectional and bidirectional jerk).
  
  
  CONCLUSIONS
  The presence of the saccadic inhibition effect in IN quick phases is consistent with the idea that quick phases and saccades share a common programming pathway. This could allow quick phases to take on flexible, goal-directed behavior, at odds with the view that IN quick phases are stereotyped, involuntary eye movements.
authors: School of Psychology, Cardiff University, Cardiff, United Kingdom.
authors: James J
authors: JJ
authors: Harrison
authors: School of Psychology, Cardiff University, Cardiff, United Kingdom Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, United Kingdom.
authors: Petroc
authors: P
authors: Sumner
authors: School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom.
authors: Matt J
authors: MJ
authors: Dunn
authors: School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom.
authors: Jonathan T
authors: JT
authors: Erichsen
authors: School of Psychology, Cardiff University, Cardiff, United Kingdom.
authors: Tom C A
authors: TC
authors: Freeman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001288:Attention / Q000502:physiology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition / Q000502:physiology*; D017120:Nystagmus, Optokinetic / Q000502:physiology; D009759:Nystagmus, Pathologic / Q000151:congenital* / Q000175:diagnosis / Q000503:physiopathology; D009802:Oculomotor Nerve / Q000502:physiology; D009949:Orientation / Q000502:physiology*; D010775:Photic Stimulation; D012438:Saccades / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: infantile nystagmus; quick phase; saccade; saccadic inhibition effect