Encoding vs. retention: differential effects of cue manipulation on working memory performance in schizophrenia.
BACKGROUND
Deficits in working memory performance are among the most widely replicated findings in schizophrenia. Roles of encoding vs. memory retention in working memory remain unresolved. The present study evaluated working memory performance in schizophrenia using an AX-type continuous performance test (AX-CPT) paradigm.


METHODS
Participants included 48 subjects with schizophrenia and 27 comparison subjects. Behavior was obtained in 3 versions of the task, which differed based upon ease of cue interoperability. In a simple cue version of the task, cue letters were replaced with red or green circles. In the complex cue version, letter/color conjunctions served as cues.


RESULTS
In the base version of the task, patients showed increased rates of false alarms to invalidly cued targets, similar to prior reports. However, when the cue stimuli were replaced with green or red circles to ease interpretation, patients showed similar false alarm rates to controls. When feature conjunction cues were used, patients were also disproportionately affected relative to controls. No significant group by interstimulus interval interaction effects were observed in either the simple or complex cue conditions, suggesting normal retention of information even in the presence of overall performance decrements.


CONCLUSIONS
These findings suggest first, that cue manipulation disproportionately affects AX-CPT performance in schizophrenia and, second, that substantial behavioral deficits may be observed on working memory tasks even in the absence of disturbances in mnemonic retention.
Javitt
Daniel C
DC
Program in Cognitive Neuroscience and Schizophrenia Nathan Kline Institute for Psychiatric Research, New York University School of Medicine 140 Old Orangeburg Road Orangeburg, NY 10962, United States. javitt@nki.rfmh.org
Rabinowicz
Esther
E
Silipo
Gail
G
Dias
Elisa C
EC
D000328:Adult; D003463:Cues; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004298:Dopamine / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis* / Q000209:etiology*; D008570:Memory, Short-Term; D016202:N-Methylaspartate / Q000378:metabolism; D009483:Neuropsychological Tests; D012153:Retention, Psychology; D012559:Schizophrenia / Q000150:complications* / Q000378:metabolism; D012720:Severity of Illness Index
D016202:N-Methylaspartate; D004298:Dopamine