Reduced prefrontal oxygenation in Alzheimer disease during verbal fluency tasks

Abstract

Objective: Near-infrared spectroscopy (NIRS) is an optical method to measure changes in the concentration of oxygenated hemoglobin (O(2)Hb) and deoxygenated hemoglobin (HHb) in the vascular system of the brain tissue. Because NIRS is easy to assess and does not have any side effects, it seems perfectly suitable for functional measurements in psychiatric patients or fragile subjects. As previous research suggested changes in functional brain activation in prefrontal brain areas of patients with dementia, the aim of this study was to replicate these findings by means of multichannel NIRS.

Methods: In the present study, the authors investigated 16 patients with Alzheimer disease and 16 healthy subjects (similar in age and sex) during performance of a verbal fluency task.

Results: The results clearly showed an activation pattern during active phase as compared to baseline phase in the form of decreases in HHb and increases in O(2)Hb, with a reduced increase of O(2)Hb for patients.

Conclusion: These results indicate a diminished activation of the dorsolateral prefrontal cortex in patients with Alzheimer disease. Future research has to show whether this decreased activation pattern might be a suitable predictor for the effectiveness of treatment in dementias.