Impaired hippocampal recruitment during normal modulation of memory performance in schizophrenia.
BACKGROUND
Patients with schizophrenia demonstrate poor verbal memory, ascribed to impaired prefrontal and hippocampal function. Healthy adults can increase recall accuracy following encoding interventions, such as item repetition and the formation of semantic associations. We examined the effects of these interventions on both memory performance and retrieval-related hippocampal activity in healthy adults and patients with schizophrenia.


METHODS
Twelve patients with schizophrenia and twelve healthy control subjects participated. During study, subjects counted either the number of meanings or T-junctions in words seen only once or repeated four times. At test, O15-positron emission tomography scans were acquired while subjects completed word-stems with previously studied items.


RESULTS
Control subjects recalled more words overall, but both groups demonstrated similar performance benefits following deeper encoding. Both item repetition and the use of a semantic encoding task were associated with memory retrieval-related hippocampal recruitment in control but not schizophrenic participants. Patients with schizophrenia demonstrated greater activation of prefrontal cortical areas during word retrieval.


CONCLUSIONS
Despite a lack of hippocampal recruitment, patients with schizophrenia showed intact modulation of memory performance following both encoding interventions. Impaired hippocampal recruitment, in concert with greater prefrontal activation, may reflect a specific deficit in conscious recollection in schizophrenia.
Weiss
Anthony P
AP
Department of Psychiatry, Massachusetts General Hospital, Boston, Massachusetts 02129, USA.
Schacter
Daniel L
DL
Goff
Donald C
DC
Rauch
Scott L
SL
Alpert
Nathaniel M
NM
Fischman
Alan J
AJ
Heckers
Stephan
S
D006624:Hippocampus / Q000098:blood supply / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology*; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000503:physiopathology; D012559:Schizophrenia / Q000150:complications* / Q000503:physiopathology*; D012660:Semantics; D014055:Tomography, Emission-Computed