This function is only slightly modified from the original topoplot.m function which is part of EEGLAB. I have used EEGLAB v6.01b while modifying the topoplot function into topoplot_connect. The main purpose is visually summarized in the attached screenshot.
I used the topoplot_connect function while developing a method for isolating transient task-induced networks in the brain at Cognitive Neuroscience Lab, DUKE-NUS Graduate Medical School. The idea can be summarized visually in the graphic included with the script.
To view help in MATLAB, type the following at the command prompt >> showdemo pn_tc_demo
My blog entry for connected topoplot is at http://praneethnamburi.wordpress.com/2011/08/18/connectedtopoplot/
If you are interested in learning more, or have comments, suggestions and/or requests for this function, please drop me an email - praneeth at mit.edu
Included a link to my blog entry on the subject and updated the 'requirements' section