HRFun is a Mac OS X application that lets you explore the construction of a canonical hemodynamic response (HRF). The HRF is typically constructed from the combination of two gamma functions, one to model the initial response and one to model the later undershoot. Using this method to create an HRF there are eight different parameters that can be used to adjust different aspects of the final response. HRFun allows you to tweak each one, allowing you to explore 'what would happen if...' in real time.
This is my first Mac OS X program to be released, so there may very well be some rough spots. Still, I did try to spend time to test and polish each aspect of the program. If you do run into trouble by all means drop me a note. If you take a look at the source code and think it is inelegant or inefficient I would like a note about that as well.