RPG: A low-cost, open-source, high-performance solution for displaying visual stimuli

Background: The development of new high throughput approaches for neuroscience such as high-density silicon probes and 2-photon imaging have led to a renaissance in visual neuroscience. However, generating the stimuli needed to evoke activity in the visual system still represents a non-negligible difficulty for experimentalists. While several widely used software toolkits exist to deliver such stimuli, they all suffer from some shortcomings. Primarily, the hardware needed to effectively display such stimuli comes at a significant financial cost, and secondly, triggering and/or timing the stimuli such that it can be accurately synchronized with other devices requires the use of legacy hardware, further hardware, or bespoke solutions.

Results: Here we present RPG (Raspberry Pi Gratings), a Python package written for the Raspberry Pi, which overcomes these issues. Specifically, the Raspberry Pi is a low-cost, credit card sized computer with general purpose input/output pins, allowing RPG to be triggered to deliver stimuli and to provide real-time feedback on stimulus timing. RPG delivers stimuli at 60 frames per second and the feedback of frame timings is accurate to 10s of microseconds.

Comparison with existing method(s): With respect to the accuracy of frame timings, the performance of RPG is at least as accurate as commonly used packages. However, the inbuilt ability to trigger stimuli and the real-time feedback of frame timings will be extremely useful for certain experiments.

Conclusions: RPG provides a simple to use Python interface that is capable of generating drifting sine wave gratings, Gabor patches and displaying raw images/video.