EyeRIS: a general-purpose system for eye-movement-contingent display control.

In experimental studies of visual performance, the need often emerges to modify the stimulus according to the eye movements performed by the subject. The eye-movement-contingent display (EMCD) methodology enables accurate control of the position and motion of the stimulus on the retina. EMCD procedures have been used successfully in many areas of vision science, including studies of visual attention or eye movements and physiological characterization of neuronal response properties. Unfortunately, the difficulty of real-time programming and the unavailability of flexible and economical systems that can be easily adapted to the diversity of experimental needs and laboratory setups have prevented the widespread use of EMCD control. This article describes EyeRIS, a general-purpose system for performing EMCD experiments on a Windows computer. Based on a digital signal processor with analog and digital interfaces, this integrated hardware and software system is responsible for sampling and processing oculomotor signals and subject responses and for modifying the stimulus displayed on a CRT according to a gaze-contingent procedure specified by the experimenter. EyeRIS is designed to update the stimulus with a delay of only 10 msec. To thoroughly evaluate EyeRIS's performance, this study was designed to (1) examine the response of the system in a number of EMCD procedures and computational benchmarking tests; (2) compare the accuracy of implementation of one particular EMCD procedure, retinal stabilization, with that produced by a standard tool used for this task; and (3) examine EyeRIS's performance in one of the many EMCD procedures that cannot be executed by means of any other currently available device.