Spatial working memory as an endophenotype for schizophrenia.
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.
Glahn
David C
DC
Department of Psychology, University of California Los Angeles, Los Angeles, California, USA.
Therman
Sebastian
S
Manninen
Marko
M
Huttunen
Matti
M
Kaprio
Joakko
J
Lönnqvist
Jouko
J
Cannon
Tyrone D
TD
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