I can think of two papers that give a good overview of mind map related things. Check out Stephen Davies "Building The Memex Sixty Years Later" and Max Volkel's "Personal Knowledge Models with Semantic Technologies". The wikipedia page on information mapping also links to a whole bunch of things similar to mind maps, although information mapping itself refers to a hyper-specific trademarked technique for writing that almost surely isn't what you're interested in. I get the impression that a lot of the "research" on this stuff is questionable, starting with the fact that mind mapping's popularity can be attributed to a pop psychologist (Tony Buzan) and continuing with the aforementioned information mapping situation. There is also the "entity-relationship" model which visualizes information but is at best "thin layer on top of the basic relational model" (C J Date, An Introduction to Database Systems, 8th ed). I think a common problem to a lot of these methods is that they don't disambiguate between the underlying model and the visual overlay and they don't have a framework for assessing the advantages of the visual representation. All this is pretty frustrating to me because I feel like there should be some more rigorous research given how popular these visual techniques are. In contrast to mind mapping, concept mapping was developed by an actual psychologist at Cornell, and I haven't looked at his stuff very thoroughly, so its possible I've just been looking in the wrong places generally.