Web links to a model associated with the paper
Model code is here
http://www.sciencemag.org/content/vol307/issue5712/images/data/1121/DC1/Machens.Matlabcode.SOM.zip
Supplementary information is here
http://science.sciencemag.org/content/suppl/2005/02/17/307.5712.1121.DC1?_ga=2.57963689.243789406.1509030571-907072911.1500650540
The model runs as is under linux/unix installations of Matlab.