title: Sinusoidal smooth pursuit eye tracking at different stimulus frequencies: position error and velocity error before catch-up saccades in schizophrenia and in major depressive disorder.
abstract: OBJECTIVE
  The aim of the present study was to ascertain the extent of impairment of position error and velocity error processing in eye tracking dysfunction in schizophrenic and depressive patients.
  
  
  METHODS
  A total of 21 schizophrenic and 19 unipolar depressive patients and 21 healthy controls were subjected to an eye tracking test with electro-oculography using horizontal sinusoidal stimuli with frequencies of 0.2-0.7 Hz. Position error and velocity error were measured over a saccade-free range of 200 ms before catch-up saccades at 50 ms intervals.
  
  
  RESULTS
  For position error, the schizophrenia patients displayed increased values particularly compared to controls, more rarely compared to depressive patients, depending on the stimulus frequency used. The increase in stimulus frequency did not lead to an increase in position error in any group of subjects over a prolonged period. For velocity error, in contrast, the study groups differed only in a few, isolated pre-saccadic intervals. The increase in stimulus frequency, however, led to an increase in velocity error in the schizophrenia patients over the entire 200 ms interval. The depressive patients did not differ notably from the controls, neither in terms of position error nor velocity error.
  
  
  CONCLUSIONS
  Eye tracking dysfunction in schizophrenia can be described as follows with regard to position error and velocity error: On the one hand, there is an increased position error tolerance largely independent of stimulus frequency, possibly due to an impairment of processing localization information. On the other hand, velocity processing is more severely impaired by an increase in stimulus frequency.
authors: Department of Psychiatry, Medical University of Graz, Auenbruggerplatz 31, Graz, Austria. karin.fabisch@medunigraz.at
authors: Karin
authors: K
authors: Fabisch
authors: Werner
authors: W
authors: Fitz
authors: Hans
authors: H
authors: Fabisch
authors: Alexandra
authors: A
authors: Haas-Krammer
authors: Gunter
authors: G
authors: Klug
authors: Stephan
authors: S
authors: Zapotoczky
authors: Hans-Peter
authors: HP
authors: Kapfhammer
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003865:Major Depressive Disorder / Q000150:complications / Q000503:physiopathology*; D004585:Electrooculography; D006801:Humans; D008297:Male; D015835:Ocular Motility Disorders / Q000150:complications / Q000503:physiopathology*; D011698:Pursuit, Smooth / Q000502:physiology*; D012438:Saccades / Q000502:physiology*; D012559:Schizophrenia / Q000150:complications / Q000503:physiopathology*