An event-related functional MRI study of working memory in euthymic bipolar disorder.
OBJECTIVE
Bipolar disorder (BD) is emerging as an illness marred by neurocognitive deficits, many of which do not resolve on recovery. Deficits affecting working memory (WM) in particular appear to be significant. WM comprises temporally separated biological processes that involve the on-line retention and manipulation of information. Previous neuroimaging studies have not sought to dissect the individual contributions of WM and examined WM subprocesses in euthymic BD. In this study, we investigated the encode, delay and response components of WM to identify the neural substrates and respective contributions to the WM deficits found in BD.


METHODS
We used event-related functional magnetic resonance imaging and a parametric WM task, incorporating 3 load conditions, to delineate individual WM subprocesses in 10 euthymic BD patients and 10 control subjects.


RESULTS
Patients exhibited attenuated patterns of activity, predominantly in frontal brain regions, across all WM components.


CONCLUSIONS
Based on the attenuated activity observed in the patients, the clinical deficits in WM found in BD may reflect broad fronto-cortico-limbic dysfunction that is not confined to any single WM component. This is important in understanding the pathophysiology of BD and for future studies on executive functions in patients with this illness.
Lagopoulos
Jim
J
Psychological Medicine Northern Clinical School, University of Sydney, Sydney, Australia. jlagopoulos@med.usyd.edu.au
Ivanovski
Belinda
B
Malhi
Gin S
GS
D000328:Adult; D001714:Bipolar Disorder / Q000453:epidemiology* / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology*; D015897:Comorbidity; D039721:Diagnostic and Statistical Manual of Mental Disorders; D019263:Dysthymic Disorder / Q000453:epidemiology* / Q000503:physiopathology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D006801:Humans; D008032:Limbic System / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis* / Q000453:epidemiology*; D009483:Neuropsychological Tests; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires