Certain misconceptions persist with respect to brain anatomy but they are being refuted by more and more evidence from sophisticated studies in brain surface mapping. Hilgetag and Barbas (cited below) represent one of many intriguing new looks at the issue, and of the many papers cited below, probably provide for the best exposition for dedicated lay readers with some science background.
Size Doesn’t Matter (All that Much)
The overall size and weight of the brain, beyond the extreme of microencephaly, are not a particularly good predictors of intellectual capability. Einsteins’ brain is said to have been about 10% smaller than average, and this clearly did not hold him back any.
Brain Weight Differences Between Genders Are Real, But Claims of Serious Cognitive Advantages by Either Sex Because of This Are Illusory
Likewise, it is true that the brains of men are predictably heavier than the brains of women, but there is a spectrum of crossover, and I can clearly imagine many men with ostensibly heavier brains who are less intelligent than any number of women with presumably lighter brains.
Computer imaging studies can correctly identify the gender of the brain through geometric scaling and weight information about 85% of the time, but do not appear to be particularly good yet at predicting intelligence per se in either or both genders, given the absence of gross abnormalities.
White Matter is Vastly More Abundant in the Brain, But Grey Matter Matters More
White matter easily makes up more than 90% of your brain by volume, but it is the thin coat of grey matter commonly called the cerebral cortex, that seems to account for virtually all of the thinking, remembering, and even a good deal of our emoting.
Relative Cortical Thickness Does Matter, Particularly in Frontal Regions Versus The Rest Of The Brain
Cortical thickness presents us with a paradox. The general thickness of the cerebral cortex correlates pretty well with intelligence across most ages, but especially so in children.
Yet virtually all cerebral cortexes tend to thin with age, and yet, as adults we do not grow less intelligent (despite what our children have to say about it).
But it turns out that having a noticeably thicker cortex as an adult in areas of the brain that are associated with higher intelligence relative to the cortical thickness in other areas of the brain of the same subject seems to be a better predictor of adult intelligence, although this finding has not been confirmed with a great many subjects (perhaps 200 thus far) yet.
For what it’s worth, given the general dictum that claims of superiority based on gender differences in brain anatomy are a tricky proposition, as they age, women tend better to preserve relative frontal cortical thickness than men as they age.
Differences in the Degree & Pattern of Brain Folding May Be Predictive of Some Abilities
In general, it appears to be better to have a greater degree of folding in your temporo-occipital lobes, and in a study of 65 healthy adult subjects, there appeared to be a pretty straightforward relationship in IQ with increased corrugation.
There is also some evidence that the relative number of folds, rather than the relative depth of the folds is also a better predictor of IQ.
Indeed, there is an increasing amount of evidence that suggests that brains that exhibit a kind of fractal pattern of developing many branching folds seem to allow for higher cognitive function in their owners.
What is particularly intriguing here is that remapping the same brain at different ages, and comparing results with increasing years of education indicates that learning new subject material and having culturally enriching experiences fosters just that sort of positive anatomical sophistication. It appears that we can improve on Mother Nature, because the brain exhibits plasticity in its folding patterns over time, particularly in youth.
Not All Folds Are Equally Good & the Timing of the Fold-Making Seems More Important Than Formerly Thought
It appears that autistics, particularly young autistic children, actually have what might be termed too many folds too early to handle them. The theory is that the overabundance and perhaps the excess of proximity of these folds at a time when the brain’s filtering processes are not ready to handle them, causes a kind of cognitive overload, sort of like too many radio transmitters broadcasting with too similar a frequency making it hard to tune one’s radio to hear any one program clearly (in the pre-HD era, at any rate).
There is already pretty good evidence that scans and comparisons of the degree of the severity of certain folding abnormalities can predict and sort out who are the low-functioning autistics, vs. the high-functioning autistics, vs. Asperger’s Syndrome patients, in the sense that well-vetted interview and test-taking techniques long used to make clinical diagnoses of severity of autism spectrum disorders correlate very well with imaging results.
There is less clear, but suggestive data that schizophrenics and bipolar patients tends to have similar cortical folding abnormalities, but the correlation of degree of severity of illness with pattern or depth, and certainly a theory of causation based on folds, are not there, at least yet.
Is there Any Hope for Curatively Refolding the Cortex?
At least one paper suggests that the brains of schizophrenics are too plastic, meaning that they are too likely to reshape their folds or do so too quickly or too often. However, even among those with some of the worse brain disorders, there are moments of relative stability, even among adolescents, and some have theorized that the cortex can then be more subtly and selectively refolded. The method is not likely to be some sort of surgery on the folds.
Rather it might just be something as utterly repetitive but potentially brain reshaping as playing video games, thousands and thousands of times. As Gary Stix notes in a commentary in Scientific American (cited below) “Grand Theft Auto IV or Medal of Honor may retrain the brain in ways its developers never imagined.”
So maybe our teenagers are smarter than us, at least about the potential for good in their endless fascination and preoccupation with even the most violent of action-packed video games.
But, that’s still an unproven theory, and I would not say sufficiently evidence-based that it should change your requests that they do their math homework, at least first.
Tony Stankus, tstankus@uark.edu Life Sciences Librarian & Professor
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