Thursday, January 10, 2013

The "New Phrenology"

Labeling something often suggests a haste to catalogue it and be done with it. It also implies some level of understanding of that which is labeled. But labels, especially pejorative ones, also commonly help to insulate one from the need to enquire further. Why would anyone who has labeled something as “trash”, for example, be bothered to read or learn anything further about it?

Every now and then, someone who is seemingly exasperated by the profusion of neurobiological facts describing a localization of some function or other in the brain, labels the whole enterprise as nothing more than the manifestation of the “new phrenology”. Nor does such labeling come only from those outside the field; sometimes the same dismissive label is used by neurobiologists themselves.

Essentially, (the old) phrenology supposed that mental faculties are localized in the brain and that an especially well developed mental faculty would result in a corresponding bump in the skull. By measurement of the skull and its bumps one would therefore be able to infer something about character, moral qualities and personality. Its originator was Franz Josef Gall, who took refuge in France after his ideas had been disapproved of in Austria and was shocked when the Institut de France, at the instigation of Napoleon, did not promote him to membership. 

There were some good reasons for dismissing phrenology and especially the use that was later made of it to promote racists ideas. But there is nothing wrong with its implicit assumption that the brain is the seat of the mind.

Those who label the tendency of modern neurobiological research to find that special cortical areas are associated with distinct functions as nothing more than a manifestation of the “new phrenology” do both the subject and themselves a disservice. That distinct cortical areas are associated with distinct functions does not mean that they can act in isolation; indeed all cortical areas have multiple inputs and outputs, both to other cortical zones as well as to sub-cortical stations and the healthy activity of an entire system is critical for a specialized area to execute its functions. It is trite to suppose, as some (non-scientists) have, that an area that is specialized for a special function, for example colour vision, can be isolated from the rest of the cortex or the brain and still mediate the experience of colour. No biologist has ever made such a claim and those outside biology who make it know nothing of biology or the brain.

It is equally untrue that the whole of the brain is involved in all its functions, as was believed in the 19th century. No one could possibly deny that there is an area of the brain that is specialized for vision or for some attributes of vision, such as visual motion; nor can anyone deny that there are areas of the brain that are specialized for audition. Nor would any reasonable person want to deny that lesions in these different zones of the cerebral cortex have different consequences.

More recently, with the advent of brain imaging studies, neurobiologists have shown that even the experience of subjective mental states does not mobilize the entire brain with equal intensity. Rather the results of such studies commonly show that a set of areas is especially involved in some subjective state or another. But activity in the areas comprising that set does not necessarily correlate only with one subjective state. An area of that set may do “double” or “multiple” duty and be active during the experience of several subjective states, even contradictory ones. But one nevertheless commonly finds that the set of areas especially active during some experiences is different from the set of areas active in another, or in other, subjective experiences, even if they share common areas.

This, of course, is a far cry from those who, usually anxious to stigmatize the findings of neurobiology, write of neurobiologists as having discovered the “love spot” or the “beauty spot” in the brain. Or to dismiss them as nothing more than “modern phrenologists”.

The “unity” of mind

A fertile terrain for questioning the localizationist claim – that cortical areas with characteristic histologies and specific sets of inputs and outputs can be associated with special functions - lies in the so-called “unity of mind” which makes us act holistically.

But let those who ridicule the efforts of neurobiologists consider what has been the greatest success of cortical studies on the one hand and what has been its greatest failure on the other.

The greatest success - which almost links the history of cortical neurobiology in one unbroken thread – is the association of special functions with distinct cortical areas. This theme has run through cortical studies since the day in April 1862 when Broca announced that the third left frontal convolution is critical for the production of articulate language.

The greatest failure has been its inability to account for how these specialized areas “interact to provide the integration evident in thought and behavior” as the American neuropsychologist Karl Lashley put it in the 1930s. He also added, however, that just because the mind is a unit, it does not follow that the brain is a unit.

Those who dismiss all these “localizationist” studies as nothing more than a “modern phrenology” may want to ask why neurobiology has failed so miserably just when it might have been expected to succeed spectacularly in light of its findings.

Perhaps a good first step in this enquiry would be to stand back – even if momentarily – and ask whether the mind is an integrated unit after all. The answer may come as a surprise.


Anonymous said...

Dear Professor Zeki-
This is a fascinating post. I am not saying anything new here but I suppose that the root of opposition to neurobiologists in their quest to draw links between regions of the brain and specific human thoughts and behaviors is individual "exceptionalism." I would not be surprised if the lay public would be willing to embrace these localization studies in animal models but reject identical findings in humans.

Of course opposition also comes from spritual and religious beliefs. There are those who cannot accept that their concept of a soul might be traced back to neuronal cell biology, a philosophical debate that has raged since the brain was first posited as the location of the mind.

My research concerns signal transduction in the retina, and the more we understand about the capabilities of non-brain tissue (given the retina is CNS, but usually people assume it is little more than a camera), the more I wonder if we will ever be able to conceive of a "whole mind" without venturing outside of the brain.

Thank you for posting this blog!

S.Z. said...

Thank you so much for your interesting comments. No doubt exceptionalism plays a part, and no doubt religion too. But the sarcasm also comes from neurobiologists who make the assumption that the brain must act as a unit to account for the supposed unity of behaviour and thought. Some neurobiologists used the term "new phrenology" to describe results on functional specialization in the visual brain of animals. They were no doubt, perhaps without even realising it, projecting their own "exceptionalism" into these studies.

Your comment about whether we will ever be able to conceive of a "whole mind" without venturing outside of the brain is especially interesting. My answer would be that we are not really able to exclude the outside when thinking about the brain. For the "outside" is reconstructed by the brain according to its own rules. By this reasoning, as Kant acutely observed (though he spoke of the mind, not the brain), there is also no "outside" without the brain. But of course the "outside" is no more a unity than the brain is.