|Are you sure this fits?|
What makes you, you? Most would contend that the organ stuck between our ears, the brain, makes us uniquely who we are. The functionality of the organic brain is the formulator of the mind and hence directs and moulds our personal identity. Therefore, if you had a complete brain transplant would you lose your personal identity? Would your body be captured by another mind and essentially 'you' would no longer 'exist'? The donor brain within a recipient body would have a separate identity belonging to the original donor body. I think most would agree the case. Otherwise you would have to assert that personal identity lies elsewhere, say in the heart. This was the predominant view in the ancient world. Successful heart transplants dictate otherwise.
But what if we transplanted part of a brain, say a lobe or just cells. Would the recipient's own consciousness be changed in some way? Could the person take on board memories of the donor? Is it possible that a hybrid personal identity could result? A melding of two minds producing an 'identity chimera'.
These sorts of questions used to be the reserve of stuffy philosophy professors to stimulate rarefied intellectual debate with their equally impractical students. Modern medicine and, especially modern surgical technique, has changed the debate and made it actually relevant to modern practical thought. For today, it is possible to insert cells, lobes, and even whole brains from a donor to a recipient. In fact, brain tissue transplants are used to treat symptoms of Parkinson's disease. And there is a consideration to use brain tissue transplants for diseases such as Alzheimer's and Huntington's.
While few would argue for whole brain transplants considering the likely transfer of donor personal identity, the debate with regard to partial brain transplants occupies a murky intellectual realm. Some argue that transplants involving the parts of the brain controlling motor function, that is to say, arm movement for instance would be okay as identity would not be affected. What about a transplant that would involve the smile reflex? Things then get more complicated as a 'smile' is often linked to emotional states and more linked to our identity than picking up a spoon. The frontal lobe is known to be influential on our personality. Would transplants within this region change who we are? Neuroscientists are only just beginning to fathom the higher functions of the brain. However, evidence to date suggests that individual memories are not just confined to a small well defined region but appear to be spread out and diffuse. So, for instance, destroying part of the brain where a particular memory lies does not necessarily destroy that memory as it can be retrieved from other regions of the brain.
And if things weren't complex enough, some philosophers argue that we do not have an adequate definition of 'personal identity'. And if you don't know what you are talking about, how can the discussion begin? Given the confusion and basic lack of scientific knowledge the discussion on brain tissue transplantation is likely to remain contentious. However, the fact that partial transplants have showed medical promise in the treatment of Parkinson's and are likely to be utilised in other brain disorders it behoves the philosophers and neurosurgeons to initiate a dialogue. But would they actually understand what their counterpart was saying? Perhaps what is needed is a human with half the brain of a philosopher and the other from a brain surgeon. What do you think the end result would be? - I predict a moron.