Shape-Shifting: The New Phrenology

Anatomical and connectivity patterns in brains correlate with behavior patterns.

Remember phrenology? This was the reading of people's traits and destinies in the shape of their skulls. While the motivation made sense, the brain being the seat of our traits and character, along with consciousness and all other mental functions, the science didn't. It turns out that the brain is far more plastic within its vault than we ever see from the outside - a skull that hardens during early childhood, long before the rest of brain and mental development is complete.

Brain visualization methods have long battled with variability. To do studies using many subjects to find some area of the brain that is "activated" during some task, the brains of those subjects need to be correlated, even though they may be shaped differently. The major landmarks of human brains are quite uniform, but on smaller scales they are not, making comparisons difficult.

But what if that variability is functional, and reflective of our capabilities and personalities? That is the subject of a recent paper, which used a style of MRI called resting state fMRI, which compares brains when they are not doing anything in particular, to see how different areas fire in relation to each other. We have what is called a "default network", which hums along even when we are consciously not doing anything. As any meditator knows, emptying the mind is virtually impossible.. there is always something going on, and these stray activities, not to mention the vast amount of unconscious processing, is the target of this rfMRI. And not just the activity per se, but the correlations between activity in different locations, which, when suitably processed, can tell us about the actual locations of functional modules of brain anatomy, and the strength of their connection.

An illustration/map of the author's data, showing variable and behavior-correlating regions by color. For example, the yellow region bottom left/right, rear of the brain, is in the parietal-occipital sulcus, associated with visually-guided behavior and planning. 

The authors devised measures of variation of region size, and correlated them with behavioral measures. Some of these were remarkably strong, indicating that small increases in a particular brain areas can have strong association with phenotypes like susceptibility to addiction and other vices, intelligence, and self-discipline. The authors focus on the technical implications of their work, which shows that inter-individual variation in functional brain structure is substantial, and makes merging/averaging for many kinds of brain studies more perilous than previously realized. It also implies that previous conclusions about variations in "coupling strength" between regions might be better interpreted as a signal of mass action caused by physically larger regions devoted to a given function.

Functions correlated with anatomical variation in the brain.

It is not surprising that, as we understand the brain better, its evident variations in effect will start to be reflected in corresponding variations in its structure and function. But it is rather disturbing as well, as this work implies that, someday down the road, brain scans may be able to tell others significant secrets about our personal lives and prospects. A "pre-crime" kind of scenario, indeed. It is, of course, one more reason to definitively separate health care from employment. It is also part of a general trend making of our lives, inside and out, an open book.

"Our results indicate that spatial variation in the topography of functional regions across individuals is strongly associated with behaviour. ... Furthermore, recent work has shown that resting state spatial maps can be used to predict task activation maps from individual subjects very accurately, and that interdigitated and highly variable subnetworks can be identified within individuals."

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"Taken together, this evidence casts doubt on the idea that more rapid technological progress alone has been the primary driver of rising inequality over recent decades, and tends to lend support to more institutional and structural explanations."