Wednesday, April 28, 2010

Ron Dennis's brain transplant

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.

2 comments:

roid said...

Dr. Krieger's partial brain transplantation experiments were of sections of the pituitary gland (a hormone producing gland within the brain) - and the "function" that was transplanted was thus solely the ability to secrete hormones. It was basically a transplant of the brain's liver or pancreas. The testable results were hormonal, not cerebral. There could have been cerebral results, but they were not tested beyond the influences of the hormones.

Also are you sure the lobes of the brain are as modular as you think? Patterns of neural activity are dictated completely by the network - by their interconnections. Due to the sheer amount of neural links that have to be severed and regrown, perhaps a lobe transplantation would irrevocably damage the original function beyond recognition.
Even small damage to the motor cortex or supporting structures can force patients to have to learn to walk all over again. So it would seem that any advantages and individuality would be lost during transplant. As an example, how would it help to be given the motor cortex of a dancer - only to have your (and the new dancer lobe's) ability to move RESET by the procedure, you'll have to learn to walk again and learn to dance again - what was the point? I think it likely that ALL neural lobes would have the same problems from such radical surgical disconnections/reconnections. Any neural linkages (incl sense of self) would be damaged beyond recognition and would need to be reset (ie: learn to walk again) to even function.
These neural systems seem more delicate that you are letting on.

Oliver said...

If Ron Dennis had his thalamus replaced, he would no longer be Ron Dennis. The surgery would have to be while Ron was very young (probably an embryo) or else the connections wouldn't line up with the cortex, and so many of his personality (and thus thalamo-cortical connections) hadn't developed or solidified yet. Then again, the cortex is very malleable... maybe connections can be integrated with some heavy stem-cell usage at an older age. In this case, Ron Dennis' core characteristics would be much like the donor's so he can't still be considered the same as the former Ron Dennis. To extend this logic further (perhaps too far), we are each not really the same person we were a month ago, since so many cortical connections have changed in that time.