title: Eye movement deficits in schizophrenia: investigation of a genetically homogenous Icelandic sample.
abstract: BACKGROUND
  Deficits in antisaccade (AS) and smooth pursuit eye movements (SPEM) are promising endophenotypes in genetic studies of schizophrenia. The Icelandic population lends itself ideally to genetic studies due to its ethnic homogeneity and well-documented genealogy. The primary aim of this study was to assess AS and SPEM performance in a large Icelandic sample. Additional aims were to investigate the relationship between AS and SPEM task performance and to assess internal consistency, within-session performance changes and effects of SPEM target velocity on performance.
  
  
  METHODS
  Patients with schizophrenia (N = 118) and healthy controls (N = 109) matched for age and gender underwent infrared oculographic assessment of AS and SPEM (at target velocities of 12 degrees , 24 degrees and 36 degrees /s).
  
  
  RESULTS
  On the AS task patients displayed significantly more reflexive errors, longer latency, increased intra-individual latency variability, and reduced amplitude gain compared to controls. On the SPEM task, patients had significantly lower velocity gain and more frequent saccades during pursuit at all velocities, but group differences in velocity gain increased with increasing target velocity. Internal consistency of performance was high for all variables in both groups (Cronbach's alpha >0.77 for AS and >0.85 for SPEM) except for AS spatial error in patients (alpha = 0.38). A moderate association was found between AS and SPEM performance. By and large, patients and controls showed similar patterns of systematic within-session performance changes.
  
  
  CONCLUSIONS
  Our findings confirm the existence of robust eye movement deficits in schizophrenia in a large sample. These measures may be studied as endophenotypes in future studies of potential schizophrenia risk genotypes in the genetically homogenous Icelandic population.
authors.affiliation: Landspitali-University Hospital, Hringbraut, 101, Reykjavik, Iceland. hmagnus@landspitali.is
authors.forename: H Magnus
authors.initials: HM
authors.lastname: Haraldsson
authors.forename: Ulrich
authors.initials: U
authors.lastname: Ettinger
authors.forename: Brynja B
authors.initials: BB
authors.lastname: Magnusdottir
authors.forename: Thordur
authors.initials: T
authors.lastname: Sigmundsson
authors.forename: Engilbert
authors.initials: E
authors.lastname: Sigurdsson
authors.forename: Hannes
authors.initials: H
authors.lastname: Petursson
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005133:Eye Movements / Q000235:genetics / Q000502:physiology*; D005260:Female; D006801:Humans; D007055:Iceland; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D011597:Psychomotor Performance / Q000502:physiology*; D011698:Pursuit, Smooth / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D012438:Saccades / Q000502:physiology*; D012559:Schizophrenia / Q000235:genetics / Q000503:physiopathology*