A Sceptical look at Functional MRI, where the limitations are discussed.
Most neuromarketers are using these scans as a way of sprinkling glitter over their products, so that customers will be persuaded that the pictures are giving them a deeper understanding of their mind. In fact, imaging technologies are still in their infancy. And while overenthusiastic practitioners may try to leapfrog over the science, real progress, which will take decades, will be made by patient and methodical researchers, not by entrepreneurs looking to make a buck.
And talking about Magnetic personalities, How a Magnet Turned Off My Speech :
Disconcertingly for me (Prof Walsh seemed unconcerned), he had difficulty finding my Broca's and only succeeded after he called for a bigger coil to be used, as powerful magnetic pulses were delivered through my skull by his colleague, Dr Neil Muggleton.
I was reciting Humpty Dumpty and hoping that all the Queens Square's neurologists and all the Queens neurosurgeons would not have to put my brain back together again.
Finally he located my Broca's and the train of pulses stopped me in my tracks. I wanted to recite the rhyme but stumbled and stuttered as my speech area was disabled.
Intriguingly, I could still sing Humpty Dumpty as he buffetted my Broca's: it turns out that singing is controlled by the right side of the brain, the opposite hemisphere to the one he stimulated.
"That is why you can sing but not talk."
This is also why some people with stroke can sing sentences, even though they cannot speak.
Prof Allan Snyder, at the University of Sydney believes TMS can act as "a creativity-amplifying machine".
But Prof Walsh is highly sceptical. "Brain stimulation does not release hidden talents and when it is used to improve things in patients, it comes at the cost of blocking some nerve pathways to encourage others."
Finally some thoughts on neurology and.. well, the usual. Over at Bilerico.
That all human behaviour has a neural basis is a truism, but isn't useful. We need to distinguish between lower-level functions that are immutable or nearly so, and much higher-level functions which are utterly changeable as the result of day-to-day experience.
Examples of the first: sexual orientation, eyesight. Examples of the second: whether to vote Republican or Democrat, whether you prefer Techno or Classical music.
And of course, there's no neat binary. We can easily distinguish extremes at both ends, but in the middle it gets blurry.
Even the most basic functions are somewhat mutable. Case in point, a man who has woken up from a multi-decade coma. His neurology differs from any other human on the planet, with parts of the brain re-wired over decades so the speech centre isn't where speech is any more. Then there those who have suffered traumatic brain injury, losing over 40% of their brain mass, and much of the rest being disrupted. Some are still able to think in nearly the same way as they were before.
Against those handful of cases, and the much larger sample where some neural deficits caused by disease and trauma have been "wired around", there are tens of thousands where even small lesions in specific areas have caused devastating and permanent cognitive deficits.
In theory, it may be possible for even some basic injuries at the hypothalamic layer to heal, given time. But as such injuries often stop the patient from breathing, or having a heartbeat, they don't have the decades needed.
So although nearly everything is mutable in some individuals to a tiny extent, in practice, much is not, not at all, not in the slightest.
Gender Identity in those who are strongly gendered is very basic. In those who are weakly gendered, close to the line, whether they appear more F than M or the reverse is determined by progressively higher and higher level functions, and will need progressively less and less heroic measures to change.
Those with classic HBS in the strong sense, it's really basic. You can torture them, psychoanalyse them, give them aversion therapy (the full Clockwork Orange treatment), totally disrupt their neurology with psychotropic drugs, even carve out pieces of their frontal lobes, and you won't do a thing to it. And all have been tried at one time or another, this isn't theoretical, alas.
A good but imperfect metric for HBS is desire for surgery. It's imperfect because although body-image is closely coupled to gender identity, it appears not to be perfectly so, and this is where I differ from proponents of the strong form of HBS theory. Some who desire surgery will do so for legal reasons, or so they can be sexually functional, not because it causes great discomfort.
Others can be quite comfortable with a strongly gendered mind, but an ambiguous or cross-gendered body. They don't care what they have, as long as it works. Many Intersexed people are in this category. I suspect that many "non-ops" are too, but lacking data, this is a mere conjecture, as is much of what I'm saying.
There are people whose general gendering is significantly weaker, yet whose body image is so strongly sexed, they will move heaven and earth to have the right body configuration, one that matches their mind. This can easily be mistaken for AG/AA, but unlike a fetish, it's a product of deep neural processes, not high-level ones. To say that it's akin to apotemnophilia, the desire for limb amputation when the body-image is defective, is technically true, but highly misleading. So misleading, you can treat it as false.
A far more accurate view is to say that it's akin to the desire of an amputee or someone with a congenital defect to have the missing limb restored, so the body images match. It restores function, not removes it.
Whether apotemnophilia or its healthy converse is a low-level or high level function probably varies. A beggar in a 3rd world country may desire amputation in order to beg more effectively ("high level"). One in a modern country may just be psychotic (also "high level" if it's treatable by anti-psychotic drugs etc).
A desire for limb restoral could be not because of any inate discomfort, but because of the practical difficulties of wheelchairs, crutches, and artificial limbs (also "high level").
Many cases though are probably low-level, and in those rare cases of intense low-level apotemnophilia, amputation of a perfectly healthy limb may be justifiable on humane grounds. Some doctors seem to think so.
Those amputees whose intense discomfort with their situation results from low-level mismatch with body image, and who are unable with current technology to regrow limbs, often suicide, despite having an objectively reasonable life in most ways. The comparison with those with HBS is unavoidable.
Fortunately, those cases appear rare. The discomfort can be lived with, and with sufficient therapeutic help to accept the situation, the "higher level" functionality can to some extent mask the "low-level" discomfort, with coping behaviour. Such a conflict causes its own problems though, and again, you get the same kinds of thing happening with those who are not classically transsexual, but have "gender issues" and will never transition.
It all fits in a common pattern of informal clinical observations. But without harder data to back it up, all it's useful for is as the basis for research, or possibly treatment in areas where we don't have the faintest idea what we're doing and lack any other explanation.
About the only area where we do have data hard enough to be useful as the basis of a therapeutic regime is in classical HBS. And even then, some will deny that.