The Influence of Phosphene Synchrony in Driving Object Binding in a Simulation of Artificial Vision.

Electrical microstimulation techniques used in visual prostheses are designed to restore visual function following acquired blindness. Patterns of induced focal percepts, known as phosphenes, are achieved by applying localized electrical pulses to the visual pathway to bypass the impaired site in order to convey images from the external world. Here, we use a simulation of artificial vision to manipulate relationships between individual phosphenes to observe the effects on object binding and perception. We hypothesize that synchronous phosphene presentation will facilitate object perception as compared to asynchronous presentation. A model system that tracks gaze position of normal, sighted participants to present patterns of phosphenes on a computer screen was used to simulate prosthetic vision. Participants performed a reading task at varying font sizes (1.1-1.4 logMAR) and under varying levels of phosphene temporal noise while reading accuracy and speed were measured. Reading performance was significantly affected by temporal noise in phosphene presentation, with increasing desynchronization leading to lower reading scores. A drop in performance was also observed when the total latency between the gaze position and phosphene update was increased without adding temporal noise. Object perception (here, text perception) is enhanced with synchronously presented phosphenes as compared to asynchronously presented ones. These results are fundamental for developing an efficient temporal pattern of stimulation and for the creation of high-fidelity prosthetic vision.