Sensory substitution
Sensory Subsitution is the principle to transform characteristics of one sensory modality into stimuli of another sensory modality. It is hoped that systems that base on sensory substitution can help handicapped people to restore the ability to perceive a certain sensory modality.
A sensory substitution system consists of three parts: a sensor, a coupling system, and a stimulator. The sensor records stimuli from one sensory modality and gives them to a coupling system which interpretes these signals and transmits them to a stimulator
The research on sensory substitution raises many questions concerning human perception and the plasticity of the human brain.
Applications
Applications are not restricted to handicapped persons, e.g. artistic presentations, games, and augmented reality. Substitution may occur in different Some examples are substitution of visual stimuli to audio or tactile, audio to tactile. Most popular are probably Paul Bach-y-Rita's Tactile Vision Sensory Subsitution (TVSS) and Peter Meijer's Seeing with Sound approach (The vOICe).
Technical developments, as miniaturization, electrical stimulation help the advance of sensory substitution devices.
Tactile Vision Sensory Substitution
The TVSS converts the image from a video camera into a so-called tactile image. The tactile image is produced by four hundred activators placed either on the back, on the chest, or on the brow. The activators are solenoids of one millimeter diameter.
In experiments, blind (or blindfolded) subjects equipped with the TVSS can learn to detect shapes and to orient themselves. In the case of simple geometric shapes, it took around 50 trials to achieve 100 percent correct recognition. To identify objects in different orientations requires several hours of learning.
Seeing with Sound Sensory Substitution
The vOICe converts the image from a video camera into a so-called soundscape. Views are typically refreshed about once per second while associating height with pitch and brightness with loudness in a left-to-right stereo scan of every camera snapshot. The effective image resolution in sound is up to several thousand pixels as can be proven by spectrographic analysis.
Criticism
It has been argued, the term "substitution" was misleading, as it was merely an "addition" or "supplementation" not a substitution of a sensory modality.