Noncontact brain activity measurement system based on near-infrared spectroscopy.

We have developed a noncontact brain activity measurement system based on near-infrared spectroscopy. With this system, phosphor is placed on the scalp of the forehead and irradiated only by excitation light that has propagated in tissue. Only fluorescence emitted by the phosphor is detected, while the excitation and disturbance lights are cut using optical filters. This configuration resolved the problem of the signal-to-noise ratio loss induced by the disturbance light. The changes in hemoglobin of the human brain were measured during a working memory task, and typical time course data were obtained. [ABSTRACT FROM AUTHOR]