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Fabrizio Santini, Gabriel Redner, Ramon Iovin, Michele Rucci; A general purpose system for eye movement contingent display control. Journal of Vision 2005;5(8):594. doi: 10.1167/5.8.594.
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In experimental studies of visual functions, the need often emerges for modifying the stimulus according to the eye movements performed by the subject. The methodology of eye movement contingent display (EMCD) enables accurate control of the position and motion of the stimulus on the retina. It has been successfully used in many areas of vision science, including studies of visual attention and eye movements and the physiological characterization of neuronal response properties. EMCD control is also crucial in a variety of applications ranging from augmented information displays to aids for subjects with visual impairments. 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 have prevented a widespread use of EMCD control.
We have developed a general-purpose system to perform EMCD experiments on a personal computer, which combines flexibility, simplicity of use, and low cost of the components. Based on a Digital Signal Processor with analog and digital interfaces, this integrated hardware and software system ensures real-time performance with refresh rates up to 200 Hz. It is responsible for sampling and processing oculomotor signals and subject responses, and communicating with the graphic card on the host PC to allow real-time generation, visualization, and gaze-contingent modification of visual stimuli. A high-level programming language makes the system accessible to users with no real-time programming experience. We show system performances in a number of EMCD procedures. In particular, we compare the quality of retinal stabilization (a procedure in which the stimulus is moved in a way that eliminates eye movements) produced by the system to that of a stimulus deflector directly coupled to a Dual Purkinje Image eyetracker.
Demos of this system can be downloaded from:
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