Abstract
Depression has been known to reduce the prefrontal activity associated with the execution of certain cognitive tasks, although whether a temporarily depressed or anxious mood in healthy individuals affects the prefrontal blood oxygen level during cognitive tasks is unknown. Combining the measurement of prefrontal activity with near-infrared spectroscopy (NIRS) and the two cognitive tasks, namely the letter version of the verbal fluency test (VFT-l) and the Stroop test, we measured the effect of a depressed or anxious mood and gender on the changes in the prefrontal oxygenated hemoglobin (Oxy-Hb) levels during those cognitive tests in healthy individuals. Depressed mood or anxious mood was assessed by the Hospital Anxiety and Depression Scale (HADS). Thereby we aimed to explore the possibility of NIRS measurement for detecting the early subclinical manifestation of major depression. Moreover, we examined the possible relationships between prefrontal activation and the functional Val66Met polymorphisms of the brain derived neurotropic factor (BDNF) gene and serum BDNF level. As a result, the increased prefrontal Oxy-Hb levels during cognitive tasks were significantly correlated with the severity of depressed mood in males. The course of the prefrontal Oxy-Hb increase was different depending on the cognitive tasks, i.e., the VFT-l or the Stroop test, in both genders. Correlations of BDNF genotype and serum BDNF level with the prefrontal Oxy-Hb levels during those cognitive tasks were negative. Our results suggest that the early subclinical manifestation of depressed mood in males might be detected by the NIRS measurement, which is not correlated with the individual properties of BDNF.
Highlights
Depression is a common psychiatric disease and results in considerable social-economic burdens due to loss of productivity [1,2,3]
Our results suggest that the early subclinical manifestation of depressed mood in males might be detected by the near-infrared spectroscopy (NIRS) measurement, which is not correlated with the individual properties of brain derived neurotropic factor (BDNF)
We examined the correlation of changes in the prefrontal oxygenated hemoglobin (Oxy-Hb) levels measured by NIRS during cognitive tasks with depressed or anxious mood, gender, Val66Met polymorphisms of the BDNF gene and serum BDNF level in basically healthy individuals
Summary
Depression is a common psychiatric disease and results in considerable social-economic burdens due to loss of productivity [1,2,3]. Near-infrared spectroscopy (NIRS) is a non-invasive method of measuring the relative change in the concentrations of oxygenated and deoxygenated hemoglobin (Δ [Oxy-Hb]) and Δ[DeOxy-Hb], respectively), which are closely correlated to the neural activity of the brain [6] Using this technique, altered prefrontal activation has been reported in various psychiatric diseases such as schizophrenia, major depression, bipolar disorder and anxiety disorder [7]. In the case of major depression, a reduced increase of the dorsolateral prefrontal Oxy-Hb level compared to healthy controls during the letter version of the Verbal Fluency Test (VFT-l-l) as determined by the measurement of NIRS has been reported repeatedly [8,9,10] It has not been clarified whether a temporarily depressed or anxious mood in healthy individuals affects the frontal blood oxygen level during cognitive tasks.
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