Vision substitution and moving objects tracking in 2 and 3 dimensions via vectorial electro-stimulation of the tongue

Vision substitution by electro-stimulation has been studied since the 60's. Camera pictures or movies encoded in gray levels are displayed via an electro-stimulation device at the surface of a body part, e.g. the skin or the tongue. Medico-technical devices are developed on this principle to take care of sensorimotor handicaps like blindness or equilibrium, or to guide precise acts like in surgery. We propose here to reduce the complexity of the displayed information to vectorial encoded 2D, but also 3D, scenes projected on the tongue via a Tongue Display Unit of 12x12 electrodes. Such vectorial encoding presents the advantage to furnish to the subjects only useful informations so as to increase the quality of recognition of 2D or 3D scenes and to reduce their cognitive load, i.e. the latency of time-to-recognition of such scenes. In the present experimental trimodal (normal vision, TDU vision substitution, or both) study on healthy people we show that the subjects are able to perceive correctly the orientation of motionless sparkling lines and to follow the trajectory of moving objects into dynamic 2D or 3D scenes. These experiments also allowed us to show the influence of the vision modality: standard deviations on the answers, moving object tracking accuracy, and response times increased consequently in case of bimodal stimulation.