title: Spatial working memory as an endophenotype for schizophrenia.
abstract: BACKGROUND
  Spatial working memory impairments are among the neurocognitive deficits that may mark genetic predisposition toward schizophrenia. We previously reported that impairment on the spatial span subtask of the Wechsler Adult Intelligence Scale-Revised increased in a dose-dependent manner with increasing genetic predisposition toward schizophrenia in a sample of discordant twins; however, it remains to be determined whether these deficits reflect difficulties with encoding, maintenance, manipulation, time-tagging of visual spatial information, storage capacity, or complex motor response.
  
  
  METHODS
  We developed a spatial delayed response task in which memory set size was parametrically varied, holding constant manipulation and decision processes. We then reassessed 80 of the previously studied twins (17 probands with 8 monozygotic co-twins and 13 dizygotic co-twins, and 42 healthy twins).
  
  
  RESULTS
  The spatial delayed response task was sensitive to genetic loading for schizophrenia but did not provide evidence for capacity limitations in probands or their co-twins.
  
  
  CONCLUSIONS
  The findings suggest that deficits in the encoding or storage aspects of short-term spatial mnemonic processing may be an effective endophenotypic marker for schizophrenia.
authors.affiliation: Department of Psychology, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Glahn
authors.forename: Sebastian
authors.initials: S
authors.lastname: Therman
authors.forename: Marko
authors.initials: M
authors.lastname: Manninen
authors.forename: Matti
authors.initials: M
authors.lastname: Huttunen
authors.forename: Joakko
authors.initials: J
authors.lastname: Kaprio
authors.forename: Jouko
authors.initials: J
authors.lastname: Lönnqvist
authors.forename: Tyrone D
authors.initials: TD
authors.lastname: Cannon
mesh_terms: D005260:Female; D008040:Genetic Linkage; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D010641:Phenotype; D012559:Schizophrenia / Q000235:genetics / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D013037:Spatial Behavior; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D014888:Wechsler Scales