The disorder is the subject of a debate between psychiatrists and neuroscientists about whether the brain physiology causes the psychiatric condition or whether the causality runs in the other direction...
Columbia University psychiatrist Michael First helped pioneer the identification of the disorder and his latest research suggests it’s just a subset of a larger psychiatric condition in which people become fixated on being disabled. On the other hand, Paul McGeoch’s recent work... seems to explain the disorder as a purely neurological disease resulting from a malfunctioning right parietal lobule, which appears to maintain the mind’s body map. His lab used fMRI to determine that four self-reported BIID patients’ right parietal lobules didn’t light up when their unwanted limbs were touched. Normal people’s did.
"Oh, this is certainly a breakthrough. We were stunned by the results," David Brang, a graduate student who co-authored a paper on the study with McGeoch, said recently on the Australian television show on which Vickers told his amazing story. "It’s very clear that this is a neurological phenomenon when it always been thought of as a psychological issue."
I wonder what he means? Are psychological and neurological explanations supposed to be competing, mutually exclusive explanations? Psychological events are grounded in brain events, after all, so why don't these fMRI studies simply indicate how the psychological disorder is realized in the brain?
[Dr. First] is, however, not yet convinced that a deficit in the right parietal lobe causes BIID. It's also possible that a strong desire to amputate a limb could transform neural circuitry in a brain region responsible for body image, he says. "There's a chicken-and-egg problem here."
Or is it more of a chicken and atoms-arranged-chickenwise (or "forest and trees") problem? Perhaps we could pin down a point of substantive disagreement if we focused on a single 'level' of explanation, say the neural level, throughout. Perhaps the point is that the neurologists are claiming that the disorder has a simple neural manifestation, whereas the psychiatrists think that the neural manifestation will be much more complex (effectively claiming that deficits in the "brain region responsible for body image" were caused by prior neural events that are best integrated and understood if we 'zoom out' to the level of psychology).
Simply put: if your mind is not how it ought to be, then neither is your brain, since the one gives rise to the other. So every psychological disorder is, in some broad sense, also a neurological disorder. But we can still draw important distinctions here. In particular, a disorder may be apparent as such at the level of the brain, i.e. in a way that's recognizable when looking at it "as" a brain, using purely neurological vocabulary. Or the problem may instead reside in more complicated neural patterns that are better captured using psychological vocabulary. There's a real question which of these two levels of explanation better captures and unifies the relevant phenomena.
So we can understand 'psychology vs. neurology' debates substantively if they concern this question of what level of abstraction unifies the disorder. Are the causes of BIID alike in respect of their superficial neurological form, or must we pull back to the level of psychology before their commonality comes into view? In effect, we may then call 'neurological' the problems that have a relatively simple neural manifestation, and reserve the competing term 'psychological' for disorders that are more unified at the higher level of abstraction offered by psychology.
Does that sound right?