A LOW-COST VGA-BASED VISUAL STIMULUS GENERATION AND CONTROL-SYSTEM

A flexible visual stimulus system has been developed for neuroscience research that uses low-cost and widely available personal computer hardware. The system has many advantages over those that rely upon traditional optical and mechanical methods, including size, flexibility and spatiotemporal resolution. The system is designed around an IBM-compatible personal computer, equipped with a VGA graphics card and a VGA monitor or projector. A set of assembly language routines has been developed for the setup and control of the graphics hardware so that images are generated and then moved with single pixel/single frame resolution. Two variations of this system are described. One version enables a stimulus on the display monitor to be imaged directly on the retina in vitro during spike recordings; the other variant back-projects an image onto a tangential screen for in vivo testing in the awake animal. Using the latter approach, the image can be positioned on the retina as the eye continues to move.