Phosphene mapping techniques for visual prostheses

Mapping of the visual world onto the visual system occurs in a highly ordered manner, yet with substantial interindividual variability. Since the retinal map of the scene at the photoreceptor level is fully determined by the optical projection of the eye, it is likely that a proximal map generated by a retinal prosthesis closely adheres to the same geometric projection. Once the nerve signals enter the optic nerve, this orderly map is redistributed, and while maps at more proximal levels still follow general rules, special mapping techniques in individual LGN or cortical prosthesis recipients will be required to allow reconstruction of spatial-relationships in the outside world by means of a disorderly array of phosphenes. This chapter provides an overview of mapping techniques that have been used in a number of laboratories; discuss the strengths and weaknesses of each; and suggest ways in which various techniques can be combined.