A near-infrared spectroscopy study of prefrontal cortex activation during a verbal fluency task and carbon dioxide inhalation in individuals with bipolar disorder.
OBJECTIVE
There is evidence of prefrontal cortex (PFC) dysfunction in patients with bipolar disorder (BP). Magnetic resonance and neuropathological studies show abnormalities of the brain microvasculature in patients with BP. However, the underlying biological mechanisms are not well understood. We investigated the relationship between activation of the PFC during a cognitive task and the vascular function in response to a physiological task in patients with BP.


METHODS
Fourteen euthymic patients with BP and 14 control subjects matched for age, sex, and education were recruited. We examined the response of the PFC during a verbal fluency task and during 5% CO(2) inhalation using a 24-channel near-infrared spectroscopy imaging system to measure alteration of oxygenated and deoxygenated hemoglobin.


RESULTS
The BP patients showed a significantly lower level of PFC activation during the cognitive task compared to the healthy controls, but the task-performance of the BP patients was not significantly different from that of the controls. The vascular response of the BP patients to CO(2) was not significantly different from that of controls.


CONCLUSIONS
This study suggests functional hypoactivation of the PFC during a cognitive load in patients with BP while they are in a euthymic state. The mechanism of this hypoactivation is different from that of vascular regulation in response to a physiological stimulus.
Matsuo
Koji
K
Department of Neuropsychiatry, Graduate School of Medicine, The University of Tokyo, Tokyo. matsuo-tky@umin.ac.jp
Kouno
Toshiaki
T
Hatch
John P
JP
Seino
Kai
K
Ohtani
Toshiyuki
T
Kato
Nobumasa
N
Kato
Tadafumi
T
D000328:Adult; D001714:Bipolar Disorder / Q000473:pathology* / Q000503:physiopathology; D001931:Brain Mapping; D002245:Carbon Dioxide / Q000008:administration & dosage*; D016022:Case-Control Studies; D004333:Drug Administration Routes; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007807:Language Tests; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D017397:Prefrontal Cortex / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D019265:Spectroscopy, Near-Infrared; D013997:Time Factors; D014705:Verbal Behavior / Q000502:physiology*
D006454:Hemoglobins; D002245:Carbon Dioxide