A brain-computer interface (BCI) is a device that provides a user with an alternative means of interactive communication, rather than the usual modes via physical gestures/speech. Thus it acts as a neural prosthesis bypassing the normal output pathways of the brain, i.e. spinal cord and periphery cascade. An optical BCI uses optical means of determining the user's mental intent, e.g. to turn on a light switch, by spectroscopic analysis of the intact brain
