[Noninvasive higher-order brain-function imaging by near-infrared spectroscopy]

The simultaneous position encoding method for optical topography was developed. Each channel has dual-wavelength optics to separately determine the changes in oxy-hemoglobin and deoxy-hemoglobin concentrations around their isobestic points at 805 nm. Part of the incident light penetrates the scalp and skull and is reflected from brain tissues including the cerebral cortex. Any change in the light extinction is mainly due to changes in the oxy-hemoglobin and/or the deoxy-hemoglobin concentration during the activation of a functional area linked to a neuronal activity. Unlike conventional functional imaging methodologies, it can be used for behavioral studies because the flexible optical fibers allow a subject to move, and a very light and compact system can be made. Noninvasive dynamic optical topography has a wide variety of applications from basic science to clinical medicine. Several applications, such as the study of the Broca and Wernicke language areas, the assessment of the dominant hemisphere of the brain, epilepsy focus determination, and sleep studies are reported. We also tested a 14-month-old baby with a extremely abnormal brain.