VCRDM stands for Variable Coherence Random Dot Motion, is a zip file containing a library of codes for creating variable coherence random dot motion for visual experiments, and uses with latest version of psychtoolbox on Mac OS X.

It is based on the dots patches originally created by Tony Movshon, and was created by Maria Mckinley, who previously worked in the lab of Dr. Michael N. Shadlen. This software has been tested, and is used in our lab regularly with virtually no dropped frames. It is pretty well documented. It includes software for making the dot patches and targets, as well as a full experiment procedure for a keypress motion discrimination task. The Kill and StartUpdateProcess commands have been removed as they are not necessary in newer versions of Mac OS X. If you are using something older than 10.4.4 tiger, make sure that the automatic software update for Mac is turned off in preferences, or it could pop up in the middle of an experiment.

Once you download and expand the zip file, put it somewhere sensible (the same place as the directory for Psychtoolbox is probably a good place). Then just add the directory to your matlab path. Checkout the readme and contents files for more information as to what is included and how to use it.

For Mac OS 9, the corresponding code is here.