Not many people use the mind map concept in the lean six sigma system. It is a method to document ideas that can be compared to brainstorming, or possibly affinity diagrams. You start with a center idea or issue and then the related items branch off the center, like the tendrils of a synapse.
If you have never seen it, look it up on wikipedia or other sources. Forrest and I are in the middle of using this tool to describe the Integrated Enterprise Excellence (IEE) system. It is one of our efforts to learn and try new concepts to see if they should be included in the IEE Body of Knowledge.