Reduced capacity but spared precision and maintenance of working memory representations in schizophrenia.
BACKGROUND
Working memory deficits are considered a core feature of schizophrenia. Several recent integrative articles have offered mechanistic computational and neurobiological models of the origins of this cognitive deficit.


OBJECTIVE
To test predictions of these models using a new experimental paradigm from the basic science literature that makes it possible to determine whether patients with schizophrenia show (1) deficits in working memory storage capacity, (2) deficits in the precision of working memory representations, and (3) an amplification of these deficits as the retention interval increases.


METHODS
Case-control design. All subjects performed a color working memory test in which they were asked to recall 3 or 4 items after a 1- or 4-second delay. All subjects also received a standard measure of intelligence and the Matrics Consensus Cognitive Battery.


METHODS
A tertiary care research outpatient clinic. Patients A total of 31 clinically stable patients with a DSM-IV diagnosis of schizophrenia or schizoaffective disorder and 26 healthy volunteers participated. The 2 groups were similar in age, sex, and ethnicity distribution.


METHODS
(1) The number of items stored in working memory and (2) the precision of the working memory representations.


RESULTS
Patients showed a clear reduction in the number of items stored in working memory. Patients did not differ from controls in the precision of their working memory representations. There was no evidence of delay-related amplification of impairment in either capacity or precision.


CONCLUSIONS
Patients do not show the type of imprecision or delay-dependent amplification of impairment that is predicted on the basis of current models of the neurobiology of schizophrenia. The models need to be revised to account for a pure reduction in the number of items that patients are able to store in working memory.
Maryland Psychiatric Research Center, Baltimore, MD 21228, USA. jgold@mprc.umaryland.edu
James M
JM
Gold
Britta
B
Hahn
Wei Wei
WW
Zhang
Benjamin M
BM
Robinson
Emily S
ES
Kappenman
Valerie M
VM
Beck
Steven J
SJ
Luck
D000328:Adult; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D003118:Color Perception / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D008570:Memory, Short-Term / Q000502:physiology; D008959:Models, Neurological; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D017397:Prefrontal Cortex / Q000503:physiopathology; D011618:Psychotic Disorders / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D011930:Reaction Time / Q000502:physiology; D012153:Retention, Psychology / Q000502:physiology; D012559:Schizophrenia / Q000175:diagnosis / Q000503:physiopathology; D012565:Schizophrenic Psychology