Alterations in functional activation in euthymic bipolar disorder and schizophrenia during a working memory task.
Dysfunctions in prefrontal cortical networks are thought to underlie working memory (WM) impairments consistently observed in both subjects with bipolar disorder and schizophrenia. It remains unclear, however, whether patterns of WM-related hemodynamic responses are similar in bipolar and schizophrenia subjects compared to controls. We used fMRI to investigate differences in blood oxygen level dependent activation during a WM task in 21 patients with euthymic bipolar I, 20 patients with schizophrenia, and 38 healthy controls. Subjects were presented with four stimuli (abstract designs) followed by a fifth stimulus and required to recall whether the last stimulus was among the four presented previously. Task-related brain activity was compared within and across groups. All groups activated prefrontal cortex (PFC), primary and supplementary motor cortex, and visual cortex during the WM task. There were no significant differences in PFC activation between controls and euthymic bipolar subjects, but controls exhibited significantly increased activation (cluster-corrected P < 0.05) compared to patients with schizophrenia in prefrontal regions including dorsolateral prefrontal cortex (DLPFC). Although the bipolar group exhibited intermediate percent signal change in a functionally defined DLPFC region of interest with respect to the schizophrenia and control groups, effects remained significant only between patients with schizophrenia and controls. Schizophrenia and bipolar disorder may share some behavioral, diagnostic, and genetic features. Differences in the patterns of WM-related brain activity across groups, however, suggest some diagnostic specificity. Both patient groups showed some regional task-related hypoactivation compared to controls across the brain. Within DLPFC specifically, patients with schizophrenia exhibited more severe WM-related dysfunction than bipolar subjects.
Hamilton
Liberty S
LS
Laboratory of Neuro Imaging, Geffen School of Medicine, University of California Los Angeles, Los Angeles, California 90095-7334, USA.
Altshuler
Lori L
LL
Townsend
Jennifer
J
Bookheimer
Susan Y
SY
Phillips
Owen R
OR
Fischer
Jeffrey
J
Woods
Roger P
RP
Mazziotta
John C
JC
Toga
Arthur W
AW
Nuechterlein
Keith H
KH
Narr
Katherine L
KL
D000293:Adolescent; D000328:Adult; D001714:Bipolar Disorder / Q000150:complications / Q000503:physiopathology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000150:complications / Q000503:physiopathology*; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000503:physiopathology*; D012559:Schizophrenia / Q000150:complications / Q000503:physiopathology*; D055815:Young Adult