“We present a hypothetical process of mind coalescence, where artificial connections are
created between two or more brains. This might simply allow for an improved form of
communication. At the other extreme, it might merge the minds into one in a process
that can be thought of as a reverse split-brain operation. We propose that one way mind
coalescence might happen is via an exocortex, a prosthetic extension of the biological
brain which integrates with the brain as seamlessly as parts of the biological brain
integrate with each other. An exocortex may also prove to be the easiest route for mind
uploading, as a person’s personality gradually moves away from the aging biological brain
and onto the exocortex. Memories might also be copied and shared even without minds
being permanently merged.  Over time, the borders of personal identity may become
loose or even unnecessary.”

Published in the International Journal of Machine Consciousness, 2012

Full text (PDF) here.