another simulation of a 2 brain situation is individuals that have a problem with thier corpus callosum -- the connection between the 2 hemispheres of the brain. typically, this cable of neurons keeps the 2 sides in psynch - but when you break the connection, you have conflicts and issues arising out of information not being transmitted to the other side for coherent behaviour/experience.
melding 2 brains-- how abt dissociating neurons from the 2 individuals or species and letting them grow and form connections in a petri dish...the leap from here, to transplantation into an empty skulled body is a very big one....however, one can look at simple electrical responses of the melded tissue to drugs or currents...
brain transplantation experiments have been done -- where a song bird's brain was transplanted into a chick's brain -- making the chick sing! how incredibly cool is that???