Sensory substitution is a change of the characteristics of one sensory modality into stimuli of another sensory modality. A sensory substitution system consists of three parts: a sensor, a coupling system, and a stimulator. The sensor records stimuli and gives them to a coupling system which interprets these signals and transmits them to a stimulator. In case the sensor obtains signals of a kind not originally available to the bearer it is a case of sensory augmentation. Sensory substitution concerns human perception and the plasticity of the human brain; and therefore, allows us to study these aspects of neuroscience more through neuroimaging. Sensory substitution systems may help people by restoring their ability to perceive certain defective sensory modality by using sensory information from a functioning sensory modality. History The idea of sensory substitution was introduced in the 1980s by Paul Bach-y-Rita as a means of using one sensory modality, mainly taction, to gain environmental information to be used by another sensory modality, mainly vision. Thereafter, the entire field was discussed by Chaim-Meyer Scheff in "Experimental model for the study of changes in the organization of human sensory information processing through the design and testing of non-invasive prosthetic devices for sensory impaired people". The first sensory substitution system was developed by Bach-y-Rita et al. as a means of brain plasticity in congenitally blind individuals. After this historic invention, sensory substitution has been the basis of many studies investigating perceptive and cognitive neuroscience. Sensory substitution is often employed to investigate predictions of the embodied cognition framework. Within the theoretical framework specifically the concept of sensorimotor contingencies is investigated utilizing sensory substitution. Furthermore, sensory substitution has contributed to the study of brain function, human cognition and rehabilitation. Physiology When a person becomes blind or deaf they generally do not lose the ability to hear or see; they simply lose their ability to transmit the sensory signals from the periphery (retina for visions and cochlea for hearing) to brain. Since the vision processing pathways are still intact, a person who has lost the ability to retrieve data from the retina can still see subjective images by using data gathered from other sensory modalities such as touch or audition. In a regular visual system, the data collected by the retina is converted into an electrical stimulus in the optic nerve and relayed to the brain, which re-creates the image and perceives it. Because it is