NIRS trajectories in Oxy-Deoxy Hb plane and the trajectory map to understand brain activities related to human interface

NIRS trajectory method is proposed to understand brain activities engaged in mobile device operation. The trajectory is the plot of oxy- and deoxy- Hb (hemoglobin concentration) data to the Oxy-Deoxy Hb plane. Three basic trajectories and some complex trajectories are explained. Total brain activities are represented by a set of NIRS trajectories derived from NIRS channels located on the head surface. Trajectory maps of text entry to mobile phone are shown. The trajectory map increases its complexity with the increase of work task complexity, which we defined by normal and reverse order hiragana and kanji conversion entry of Japanese text. The results suggest the right brain is taking dominant roles in text and other finger activities. NIRS trajectory method can be applied further to find centers of brain activities located on the surface area of the brain. Kindly use color version in CD-ROM for better understanding of this paper.