The role of hippocampus dysfunction in deficient memory encoding and positive symptoms in schizophrenia.
BACKGROUND
Declarative memory disturbances, known to substantially contribute to cognitive impairment in schizophrenia, have previously been attributed to prefrontal as well as hippocampal dysfunction.


OBJECTIVE
To characterize the role of prefrontal and mesolimbic/hippocampal dysfunction during memory encoding in schizophrenia.


METHODS
Neuronal activation in schizophrenia patients and controls was assessed using functional magnetic resonance imaging (fMRI) during encoding of words in a deep (semantic judgement) and shallow (case judgment) task. A free recall (no delay) and a recognition task (24h delay) were performed.


RESULTS
Free recall, but not recognition performance was reduced in patients. Reduced performance was correlated with positive symptoms which in turn were related to increased left hippocampal activity during successful encoding. Furthermore, schizophrenia patients displayed a hippocampal hyperactivity during deep encoding irrespective of encoding success along with a reduced anterior cingulate cortex (ACC) and dorsomedial prefrontal cortex (DMPFC) activity in successful encoding but an intact left inferior frontal cortex (LIFC) activity.


CONCLUSIONS
This study provides the first evidence directly linking positive symptoms and memory deficits to dysfunctional hippocampal hyperactivity. It thereby underscores the pivotal pathophysiological role of a hyperdopaminergic mesolimbic state in schizophrenia.
Zierhut
Kathrin
K
Department of Psychiatry, Otto-von-Guericke University of Magdeburg, Germany.
Bogerts
Bernhard
B
Schott
Björn
B
Fenker
Daniela
D
Walter
Martin
M
Albrecht
Dominik
D
Steiner
Johann
J
Schütze
Hartmut
H
Northoff
Georg
G
Düzel
Emrah
E
Schiltz
Kolja
K
D000328:Adult; D001931:Brain Mapping / Q000379:methods; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006624:Hippocampus / Q000098:blood supply / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008569:Memory Disorders / Q000209:etiology* / Q000473:pathology*; D011939:Mental Recall / Q000502:physiology; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D011569:Psychiatric Status Rating Scales; D021641:Recognition, Psychology / Q000502:physiology; D012559:Schizophrenia / Q000150:complications*; D055815:Young Adult
D010100:Oxygen