Measurement of absolute hemoglobin concentrations of prefrontal region by near-infrared time-resolved spectroscopy: examples of experiments and prospects.

Near-infrared time-resolve spectroscopy (TRS) is an emerging method which enables the absolute hemoglobin concentration in tissue to be evaluated. In the present paper, two experiments measuring the absolute hemoglobin concentrations in the prefrontal region to estimate the local cerebral activity will be demonstrated. The results of the studies were as follows: 1) There were significant differences in the absolute hemoglobin concentrations between the groups with different traits in personalities such as anxiety, or type A behavior pattern. 2) TRS was found to be applicable to field experiments. It was revealed that in a forest environment, the activity in the prefrontal region was calmer than in a city environment. This method will provide useful information on the absolute hemoglobin concentrations and contribute to making physiological polymorphisms clear.