Development of a freeware for analysis of neuromagnetic epileptic discharges.

We developed a freeware for the analysis of neuromagnetic epileptic discharges and named it "hns_meg." It works as an executable standalone application, compatible with 32/64 bit Microsoft Windows Vista or Mac OSX 10.6. The program is designed for recordings from planar gradiometers and includes the following functions: listing of topographies of maximum gradient magnetic field ((partial differential)B) every 1 s throughout the measured time, two or three-dimensional topographical representations of (partial differential)B, and time-frequency representations based on a maximum entropy method. Coupling the first function with an appropriate frequency filter is useful in efficiently finding spikes. The last two functions are attractive for users who want to try new analytical methods different from those in commercially available software packages.