A functional magnetic resonance imaging study of working memory abnormalities in schizophrenia.
BACKGROUND
Previous neuroimaging studies of working memory (WM) in schizophrenia, typically focusing on dorsolateral prefrontal cortex, yield conflicting results, possibly because of varied choice of tasks and analysis techniques. We examined neural function changes at several WM loads to derive a more complete picture of WM dysfunction in schizophrenia.


METHODS
We used a version of the Sternberg Item Recognition Paradigm to test WM function at five distinct loads. Eighteen schizophrenia patients and 18 matched healthy controls were scanned with functional magnetic resonance imaging at 3 Tesla.


RESULTS
Patterns of both overactivation and underactivation in patients were observed depending on WM load. Patients' activation was generally less responsive to load changes than control subjects', and different patterns of between-group differences were observed for memory encoding and retrieval. In the specific case of successful retrieval, patients recruited additional neural circuits unused by control subjects. Behavioral effects were generally consistent with these imaging results.


CONCLUSIONS
Differential findings of overactivation and underactivation may be attributable to patients' decreased ability to focus and allocate neural resources at task-appropriate levels. Additionally, differences between encoding and retrieval suggest that WM dysfunction may be manifested differently during the distinct phases of encoding, maintenance, and retrieval.
Johnson
Matthew R
MR
Olin Neuropsychiatry Research Center, The Institute of Living at Hartford Hospital, Hartford, CT, USA.
Morris
Nicholas A
NA
Astur
Robert S
RS
Calhoun
Vince D
VD
Mathalon
Daniel H
DH
Kiehl
Kent A
KA
Pearlson
Godfrey D
GD
D000328:Adult; D016022:Case-Control Studies; D002755:Choice Behavior / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D008960:Models, Psychological; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood*; D017397:Prefrontal Cortex / Q000098:blood supply* / Q000503:physiopathology; D011930:Reaction Time / Q000502:physiology; D012559:Schizophrenia / Q000503:physiopathology*
D010100:Oxygen