If I'm transplanted with, e.g., Stephen Hawking's brain, would I start to think like him, or would I remain to think like me? On which, "thinking" ability depends , is it the physical structure of brain or any non physical thing?
Human brain transplants have never been performed, so any answers to what will happen are mere speculations.
Whole-head transplants have been performed on animals, the first reports go back to the 1970's (Canavero, 2013). The practice is still pursued today (e.g.., Ren et al., 2015)). Up until now, however, it has not been done in humans, and likely it never will be (source: The Guardian). This, because of medical limitations (Canavero, 2013) as well as ethical considerations (Wolpe, 217)
The biggest problem medically is the re-connection of the thousands of spinal neurons linking the brain to the rest of the body (Canavero, 2013). Further, immune responses and immediate cell death due to oxygen depletion may all further hamper the process. Nonetheless, certain groups envision it will be at one time possible in humans (Canavero, 2013).
The same limitations as with head transplants discussed above apply for a brain transplant. The thing is that with a whole-head transplant the major arteries can be quickly connected to feed the brain. With a brain transplant this also becomes a major bottle neck, making it even more difficult. Transplanting a head can be done with relative ease by sacrificing the donor and straight away stitch it to the beheaded recipient. A brain transplant needs even more steps. The big advantage of a head transplant is also that the brain, being within its own cephalon, still connects to the cranial nerves (White et al, 1975).
- Canavero, Surg Neurol Int (2013); 4(S1): S335–S42
- Ren et al., CNS Neurosci Therapeutics (2015); 21(8): 615-8
- White et al. Resuscitation 1975;4,197-210
- Wolpe, AJOB Neurosci (2017); 8(4)
- Is brain transplantation possible?
Assuming we could do a human brain trransplant and it wouldn't damage too much the recipient body or the donated brain:
The body that is currently called "your body", when it woke up, would wake up with Stephen Hawking's (or whoever's) thoughts and memories, though he may be in different "moods" than he normally is in because now he would also have your endocrine system (your glands), which would affect his brain function.
That's because our best model of how mental activity occurs is it's the brain that stores style of thinking, skills, memories and other types of mental content. This is in contrast, to, say, Aristotle's view that the brain was merely an organ for cooling the blood. Furthermore, specific brains--in terms of structure and function--give rise to specific sets of mental content.
What's the evidence for the idea that the brain is the location of mental function and that the structure and functionality of a particular brain dictates the mental content generated by that brain? A great deal indeed, but here is a smattering of evidence:
Damage to the brain causes obvious changes to mental function. One good examples of this is stroke, in which specific areas of the brain are destroyed. This can leave a person with a very specific mental deficit, such as the inability to recognize specific classes of objects, faces, or words. But there are many other ways for the brain to be changed, and along with it, personality or thinking. Tumors may have been responsible for sexually deviant behavior. On the positive side, a traumatic brain injury may have turned a man into a math genius.
Temporary changes to brain biochemistry, such as alcohol intoxication, hypoglycemia, hypercapnia (too high carbon dioxide), etc., all cause obvious and usually reliably reversible changes in mental function.
There are essentially unending examples, either in humans or animal models, that show that brains underlie mental function and that specific brains give rise to specific minds (for some non-spiritual definition of "a mind").