I am in a coma from midnight to midnight. My brain is attached to a technology that focuses on the mind of an acquaintance who lives across town. During that twenty four hour period, every mental process that occurs in her brain is transmitted to mine in real time. Thus, I am effectively in a virtual reality where I experience all her thoughts, memories, imaginings, actions, conversations, even dreams during the periods when she is asleep, and I think that I am her. When I emerge from the coma, I remember my previous life as before but my most recent memories are of her previous day because I have directly experienced it.
If done without her knowledge, a total invasion of privacy. Also voyeuristic and distasteful? I further imagine that at some times during the day she has remembered and thought about me. Thus, I now have direct knowledge of how I appear to someone else. Potentially devastating. If someone else did this during a day when I met the subject and then transferred the experience to me, then I would now have both my memories and the subject's memories of a conversation between us.
Has anyone used precisely this idea in an sf story or novel? It would seem to have considerable potential. If the mental transfers were conducted with the knowledge and consent of the subject, then they would be a way for people to share experiences and to deepen understanding.