Optical topography is a completely non-invasive technique for obtaining dynamic images of the brain during the processing of higher-order functions, including mentation. Here, “higher-order brain functions” refers to functions of the cerebral cortex, the most recently evolved part of the brain. In addition, “completely non-invasive” indicates techniques that do not harm the body, require the insertion or ingestion of foreign objects or substances, or cause any real discomfort. Near-infrared spectroscopy is used to make the measurements for optical topography. Unlike conventional brainfunction- imaging methods such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), optical topography only requires compact and portable equipment. This makes it relatively easy for anyone to observe brain activity. A further contrast is that optical topography does not require the patient to be fixed to a platform. Researchers have started to investigate the application of optical topography to the observation of brain activity in everyday life, including the viewing of television and video programs, participation in various types of games and entertainment, driving, exercising, dreaming, the experience of psychological trauma, and the gaining of insight into problems. In short, optical topography has opened up new fields of application and these continue to expand.