The recently re-installed Chairman of the McLaren Group, Ron Dennis confessed to The Economist last month that "Sometimes I think I need a brain transplant because I can drive myself absolutely bonkers."
Now, whilst Ron was, of course, engaging in rhetorical hyperbole, let us, for the sake of argument, and to advance the state of medical science, assess whether there is any sense in which Ron could actually become the lucky recipient of a brain transplant.
The immediate response is that the notion makes little sense unless one advocates a type of mind-brain dualism. The continuity of personal identity, and in particular the retention of personal memories, are dependent upon neurophysiological continuity, hence there is no sense in which Ron could have a brain transplant, because it simply wouldn't be Ron afterwards. In particular, Ron would presumably be unwilling to lose those precious memories of "[going] to bed with the vacuum cleaner going because my mum wanted the house immaculate when she got up."
However, the sense of personal identity is held in the higher brain alone, which opens up the possibility of a partial brain transplant in which Ron remains Ron, but in which he could be shorn of that troubling perfectionist streak. Remarkably, such partial brain transplants seem to be possible in principle, having been successfully performed upon mice. Dr. Dorothy T. Krieger, chief of endocrinology at Mount Sinai Medical Center in New York City, performed such experiments as far ago as 1982, taking a small piece from one brain, and dropping it into a cavity in another brain. In these experiments, the donated brain cells began to grow in the cavity, sending out nerve fibres which spontaneously connected up in the right way with the rest of the brain.
Duly encouraged by Dr Krieger's ground-breaking experiments, let us briefly remind ourselves of how the human brain is structured, in order that we might identify some candidate regions for transplantation.
As David DeGrazia eloquently explains, "We may think of the brain as comprising two major portions: (1) the 'higher brain', consisting of both the cerebrum, the primary vehicle of conscious awareness, and the cerebellum, which is involved in the coordination and control of voluntary muscle movements; and (2) the 'lower brain' or brainstem. The brainstem includes the medulla, which controls spontaneous respiration, the ascending reticular activating system, a sort of on/off switch that enables consciousness without affecting its contents (the latter job belonging to the cerebrum), as well as the midbrain and pons."
Could the cerebellum be a good candidate for transplantation? It's not essential to personal identity, but on the other hand, the cerebrum is tightly integrated with the cerebellum, and the user may find it difficult to cope with an unfamiliar cerebellum:
"The cerebellum...is responsible for precise coordination and control of the body - its timing, balance, and delicacy of movement. Imagine the flowing artistry of a dancer, the easy accuracy of a professional tennis player, the lightning control of a racing driver, and the sure movement of a painter's or musician's hands...Without the cerebellum, such precision would not be possible, and all movement would become fumbling and clumsy. It seems that, when one is learning a new skill, be it walking or driving a car, initially one must think through each action in detail, and the cerebrum is in control; but when the skill has been mastered - and has become 'second nature' - it is the cerebellum that takes over. Moreover, it is a familiar experience that if one thinks about one's actions in a skill that has been so mastered, then one's easy control may be temporarily lost. Thinking about it seems to involve the reintroduction of cerebral control and, although a consequent flexibility of activity is thereby introduced, the flowing and precise cerebellar action is lost." (Roger Penrose, The Emperor's New Mind, p490).
Whilst the cerebellum, then, should be left well alone, the various components of the lower brain seem to perform modular functions, and therefore constitute more acceptable candidates for transplantation. In particular, for those wishing to alter their desires and motives, the thalamus may be the perfect candidate, for according to neurosurgeon Wilder Penfield, it provides the content of willed action. It is impossible to engage in willed action without the thalamus communicating with the relevant part of the motor cortex in the cerebrum, and whilst the relevant part of the motor cortex can be directly stimulated to produce action, doing so will yield action without a corresponding desire to perform that action. The thalamus seems to need the conscious mind, but without the thalamus, the conscious mind has no motives.
So there we have it: Ron Dennis could, if his thalamus so desired, have his thalamus removed and replaced by the thalamus of someone else, and still be Ron Dennis.