Complexity of prefrontal cortical dysfunction in schizophrenia: more than up or down.
OBJECTIVE
Numerous neuroimaging studies have examined the function of the dorsolateral prefrontal cortex in schizophrenia; although abnormalities usually are identified, it is unclear why some studies find too little activation and others too much. The authors' goal was to explore this phenomenon.


METHODS
They used the N-back working memory task and functional magnetic resonance imaging at 3 T to examine a group of 14 patients with schizophrenia and a matched comparison group of 14 healthy subjects.


RESULTS
Patients' performance was significantly worse on the two-back working memory task than that of healthy subjects. However, there were areas within the dorsolateral prefrontal cortex of the patients that were more active and areas that were less active than those of the healthy subjects. When the groups were subdivided on the basis of performance on the working memory task into healthy subjects and patients with high or low performance, locales of greater prefrontal activation and locales of less activation were found in the high-performing patients but only locales of underactivation were found in the low-performing patients.


CONCLUSIONS
These findings suggest that patients with schizophrenia whose performance on the N-back working memory task is similar to that of healthy comparison subjects use greater prefrontal resources but achieve lower accuracy (i.e., inefficiency) and that other patients with schizophrenia fail to sustain the prefrontal network that processes the information, achieving even lower accuracy as a result. These findings add to other evidence that abnormalities of prefrontal cortical function in schizophrenia are not reducible to simply too much or too little activity but, rather, reflect a compromised neural strategy for handling information mediated by the dorsolateral prefrontal cortex.
Callicott
Joseph H
JH
Clinical Brain Disorders Branch, NIMH/NIH, Bldg. 10, Rm. 4D-20, MSC 1389, Bethesda, MD 20892-1389, USA. callicoj@intra.nimh.nih.gov
Mattay
Venkata S
VS
Verchinski
Beth A
BA
Marenco
Stefano
S
Egan
Michael F
MF
Weinberger
Daniel R
DR
D000124:Achievement; D000328:Adult; D001812:Blood-Brain Barrier / Q000502:physiology; D001931:Brain Mapping; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D017397:Prefrontal Cortex / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values; D012559:Schizophrenia / Q000175:diagnosis / Q000503:physiopathology*; D012565:Schizophrenic Psychology
D010100:Oxygen