Alterations in prefrontal cortical activity in the course of treatment for late-life depression as assessed on near-infrared spectroscopy

Aim:  To evaluate the severity of depression by measuring alterations in prefrontal cortical activity associated with mood disorders, as assessed on near-infrared spectroscopy.
Methods:  Ten of 27 subjects hospitalized for late-life depression from May 2006 to June 2007, were examined. In these 10 subjects changes in hemoglobin concentration were measured on near-infrared spectroscopy during two types of the rock, paper, scissors game as the cognitive tasks affecting prefrontal cortical activity on 2 days, including 1 day on which depressive symptoms had slightly improved due to treatment, and then on another day >4 weeks later. Severity of depression and cognitive impairment were also simultaneously assessed.
Results:  The change in oxygenated hemoglobin concentration during a difficult task (intentional loss task) was significantly larger than that during an easy task (try to win task) on the left side (left, P  = 0.010; right, P  = 0.059). On the left side there was a significant negative correlation between the ratio of oxygenated hemoglobin measurements on the second day to those on the first day, and the severity of depression on the second day (left, P  = 0.012; right, P  = 0.090). Thus, the more left prefrontal cortical activity tended to increase, the fewer depressive symptoms tended to be present on the second day of testing.
Conclusions:  Measuring of alterations in prefrontal cortical activity associated with mood disorders, as assessed on near-infrared spectroscopy, is feasible in subjects with depression.