Wednesday, June 10, 2015

Everybody Is Just A Little Twisted

Biology concepts – bilateral asymmetry, brain, ventriculomegaly, brain torque, fluctuating asymmetry, sex hormones

“Getting all your ducks in a row” actually comes
from bowling. The pins used to be known as
ducks….still are in duckpin bowling. Before pin
setting machines, people had to put the pins
down in even, straight lines so that the game was
predictable and fair. The “ducks” had to be
in “rows.”
When you are organized, you have “all your ducks in a row.” When you are calm and in control, you’re “thinking straight.” When you are doing the right things, you’re “on the straight and narrow.” When something is undiluted, like a story or whiskey, you get it ”straight.”

Basically, if something is straight, it is correct, unembellished, pure, or not perverted. So what would be the opposite of this? Twisted, of course.  Twisted tales are slightly weird or not true to the stories they are taken from. And when you're “a little twisted” you’re thinking is mentally unsound or a bit perverted. 

In modern internet slang, twisted means high and drunk, so again it means a perverted form of thinking. Not that it always has to be bad; Stephen King is truly a bit twisted, but he writes well and leads a relatively normal life. Some people bask in the sunlight of their twisted thinking.

But what if I told you that everyone's brains, and therefore everyone's thinking, is just a bit twisted? In technical terms it is called a Yakovlevian torque, but let’s not kid ourselves, it means that our brain is twisted in our skull.

First recognized by the Russian born Harvard anatomist Paul Ivan Yakovlev, the midline fissure where our two cerebral hemispheres butt up against one another doesn’t exactly follow the midline of our skull. There is a slight twist to the left, so that the right cerebral hemisphere crosses the midline to the left behind your forehead and the left hemisphere crosses over to the right side of your skull in the posterior. Everybody’s brain is just a bit out of whack!

Here is a human brain cartoon as seen from
 below from a Nature Review paper. The right
hemisphere is actually on the left side. Notice how
the frontal lobe of the right hemisphere sticks out
further? It’s the same with the occipital lobe in
back on the left lobe. In each case, they twist so
they the midline of the brain crosses the midline
of the skull. The brain is torqued to the left. 
In other words, the right side of your brain is torqued slightly forward relative to the left and this twists it out of bilateral symmetry with your skull. At least part of this is due to the larger left parietal lobe areas for speech and language that most people have on their left side (see last week’s post), but that isn’t the only source.

Several sources of asymmetry go together to produce brain torque, and it can be greater or lesser in each individual – yes, some people are more twisted than others.

Yakovlev observed that different people had different size depressions on the interior surfaces of their skull in the right anterior and left posterior (called petalias). You can imagine that with a tofu-consistency brain sitting in an opened skull, it might be hard to quickly recognize a slight twist to the left, but Yakovlev wrote about it and hypothesized on its importance.

It wasn’t until 2009 that a couple of studies (here and here) confirmed the torque using very advanced imaging techniques and alot of math. The hard part is accounting for brain position internally and skull midline externally, each of which have fluctuating asymmetries within one individual and variances between individuals. But both studies concluded that Yakovlevian torque is real. Now we just need to figure out it’s significance.

This short clip shows the loss of grey matter
(unmyelinated neurons) through development in
a person with schizophrenia. As colors move to
yellow, that indicates more loss. The hemisphere
start out asymmetric and become more so. Maybe
cases can be diagnosed earlier by watching
for asymmetries.
Even if we don’t know why our brains need to torque, we can perhaps use the observation in medicine. Some torque is normal, but too much occipital bending may be bad. Two studies from the same group have correlated excessive torque with major depression and bipolar disorder. One even related atypical torque to developmental stuttering in boys.

On the other hand, a study in autism showed that there was no correlation between autism spectrum disorders and atypical Yakovlevian torque. Well, sort of. This single study only looked at high functioning, right-handed, boys in a narrow age range. So who knows if there might be some relationship between autism and torque in other affected groups. Always be sure to take into consideration the limits of any study you read.

So torque is the norm in human brains; guys and girls both have a leftward twisted to the brain within the skull. There are many more asymmetries in brain than just the ones we have discussed; there are many examples of left > right asymmetries and some of right > left. These differences are evolutionary and are apparent even during the second trimester. But the mechanism and reason for each asymmetry may be different; some are based on gender - boy brains and girl brains are different!

This exception in bilateral symmetry is two fold; there are gender-induced differences in the brain that are both sexual dimorphic – meaning that they depend on the sex hormones or sex chromosome genes of each individual, and they are asymmetric – meaning that the gender-induced structure or function changes affect one hemisphere more than the other.

Dr.s Ruigrok, Suckling and Baron-Cohen have
collated sexual dimorphisms in brain structures.
The red areas are larger in women; the blue areas
larger in men – the girls’ should have been pink.
These differences are due to genetic, hormonal, and
environmental factors all mixed up in a big soup.
Many studies have linked prenatal androgen (male sex hormones) levels to asymmetry, but some asymmetries appear before androgen even begins to be produced. These male asymmetries are probably due to the genes expressed on the sex chromosome. A 2014 study linked the two phenomena. Apparently regional asymmetries in the male cerebrum and cerebellum are exacerbated compared to female brains through the joint action of testosterone and X-linked genes.

Male brains are more lateralized than females. Functions are segregated more strictly in male hemispheres, so perhaps it’s true that only women use their entire brain.

A few weeks ago we talked about fluctuating asymmetries – those differences in structure size and position from individual to individual. We were talking then about external asymmetries, but peoples’ brains have fluctuating asymmetries as well. One in particular may help predict neurologic disease – and it isn’t even a brain structure.

Several studies go back and forth on whether the size or asymmetry of the lateral ventricles (CSF filled spaces in the brain, see this post) can predict schizophrenia or developmental delays. A 2010 case report suggested that alone they may have no particular effect, but if mild ventriculomegaly (bigger than normal ventricles) is accompanied by atypical lateral ventricular asymmetry (the left lateral ventricle is normally a bit bigger than the right), then these may be predictive of delay and/or schizophrenia later in life.

For a more historical example of fluctuating asymmetry in the brain let’s go straight to the top – Albert Einstein. While he was alive people wondered if his brain was different from all of ours. He just thought on a different plane; his concepts were Earth shattering, yet he used thought experiments with elevators in space and passing trains.

Einstein had a brain to be admired, and I’m sure
he wouldn’t use his powers for the dark side. But
thought experiments about elevators in space and
trains passing by aside, I’m wondering what he
may have gleaned about the universe from a duel
using the force with Darth Vader.
When he died in 1955, Einstein consented to have his brain studied. The pathologist, Thomas Stoltz Harvey, did no one any favors. He weighed it, took some pictures of it, made some measurements, and then cut it up into 240 pieces. He kept some and gave a few to other pathologists. This pretty much eliminated any decent study that could have been done at the time. Thanks a lot Tom.

In 1999, a qualitative and quantitative study of the data and measurements recovered from Einstein’s brain was carried out, comparing it to 5 male and 56 female brains. The researchers’ results were shocking for what they did and didn’t find.

First, Einstein didn’t have a huge brain, it was basically the same size as everyone else’s. There weren’t extra lobes or a million times more neurons – it looked like a regular brain on first glance. But that’s where science comes in; scientists don’t stop at a first glance.

For one thing, Albert’s brain was missing a certain landmark. Without getting technical, there are two fissures (sulci) that usually pass by one another and create a little island of tissue near the temporal/parietal lobe border. Well, Einstein’s didn’t pass by one another, they merged. This allowed more room for brain tissue since there was only one fissure instead of two.

Long before he could measure the bending of light
by massive objects, Einstein thought about how
shining a light on Earth (force of gravity), and shining
a light in space elevator (force of acceleration) might
show how light illustrates general relativity. It took
long expeditions and many years, but his idea was
finally proved correct by measurement of
sunlight during an eclipse.
This is then related to the second difference they found in Einstein’s brain. His brain was about 15% wider than normal in the parietal lobes. He had more brain shoved into that area. As fluctuating asymmetries go, this is beyond huge, usually the difference might be 1-3%.

Why might this fluctuating asymmetry be important? Did it have a functional correlate? That would be hard to tell since the brain isn’t firing now. Wouldn’t it have been great if functional MRI had been around when Albert’s brain was still in Albert’s living head? I bet he could have lit up most of Princeton – but I digress.

The parietal lobe has many lateralized functions, but some of them are right in Einstein’s wheelhouse. This lobe is important mathematical reasoning, and for connecting visual, somesthetic and auditory stimuli together into a big picture.

Take all this together and what you get is that the parietal lobe is what creates mathematical relationships, conscious or unconscious, amongst the world and its moving parts. Professor Einstein was better at that than everyone else, so maybe his wider than normal parietal lobe was responsible.

Of course this doesn’t let the rest of us off the hook. Plenty of people do some awesome thinking and reasoning with very ordinary brains. As we have shown before in this blog – exercise your brain and it will become sharp. Use it or lose it.

Next week, more internal asymmetries in those bilaterally symmetric animal bodies. Your lungs are for breathing, but right and left don’t participate equally – and there’s some cool math involved, so warm up your parietal lobes.

Maller, J., Anderson, R., Thomson, R., Rosenfeld, J., Daskalakis, Z., & Fitzgerald, P. (2015). Occipital bending (Yakovlevian torque) in bipolar depression Psychiatry Research: Neuroimaging, 231 (1), 8-14 DOI: 10.1016/j.pscychresns.2014.11.008

Maller, J., Thomson, R., Rosenfeld, J., Anderson, R., Daskalakis, Z., & Fitzgerald, P. (2014). Occipital bending in depression Brain, 137 (6), 1830-1837 DOI: 10.1093/brain/awu072

Mock, J., Zadina, J., Corey, D., Cohen, J., Lemen, L., & Foundas, A. (2012). Atypical Brain Torque in Boys With Developmental Stuttering Developmental Neuropsychology, 37 (5), 434-452 DOI: 10.1080/87565641.2012.661816

Savic, I. (2014). Asymmetry of cerebral gray and white matter and structural volumes in relation to sex hormones and chromosomes Frontiers in Neuroscience, 8 DOI: 10.3389/fnins.2014.00329

Witelson, S., Kigar, D., & Harvey, T. (1999). The exceptional brain of Albert Einstein The Lancet, 353 (9170), 2149-2153 DOI: 10.1016/S0140-6736(98)10327-6

For more information or classroom activities, see:

Gender differences in brains –

Yakovlevian torque –

Albert Einstein’s brain –