The brain is not symmetrical — researchers have revealed new insights about the brain

At first glance, the human body seems symmetrical: two arms, two legs, two eyes, two ears, and even the nose and mouth seem to be reflected on an imaginary axis that separates
most people's faces.
Finally, the brain is divided into two almost equal sized parts, with grooves and bulges following a similar pattern
.
However, the initial impression is misleading because there are small, functionally related differences
between the left and right brains of different brain regions.
These two hemispheres have different functional specializations
.
For example, most people process language primarily on their left side of their brain, while spatial attention is primarily on their right side
.
In this way, the work can be more effectively distributed to the parties and the overall scope of the mandate is expanded
.
        

However, this so-called lateralization, the tendency of brain regions to process certain functions is located more on the left or right side of the brain, varies
from person to person.
It's not just that a few people's brains are mirror inverted
compared to the majority.
Even people with classical brain structures have varying degrees of asymmetry
.
Previous research has shown that this, in turn, may have an impact
on the function itself.

For example, dyslexia is characterized by the lack of left asymmetry
in certain language areas.
Inadequate brain lateralization can also lead to conditions
such as schizophrenia, autism spectrum disorder, and childhood ADHD.

Until now, however, it was unclear how much of the differences in brain asymmetry between individuals were genetic and how much was caused
by different needs.
Also, did similar brain asymmetry traits exist in monkeys?

Scientists at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) and Forschungszentrum Juelich (FZJ) have now studied the asymmetry of functional gradients, describing the smooth axis
of change in brain function in the cortex.
They found subtle changes
in the functional organization of the left and right brain regions.
On the left, the area involved in language processing is farthest from
the area involved in sight and sensation.

On the right side of the brain, the so-called frontopatometric neural network, responsible for attention and working memory, is farthest
from these sensory regions.
The researchers also found that individual differences in these functional arrangements are heritable, meaning they are influenced
to some extent by genetic factors.
At the same time, a large part of this asymmetry in the human brain cannot be explained
by genetic factors.
This means that some asymmetry is at least partly influenced
by personal experience.

In addition, the team found that human brains are more asymmetrical
than monkey brains.
"The observed functional asymmetry likely reflects the interaction of genetic and non-genetic influences from an individual's experience," explains Bin Wan, a doctoral student at MPI CBS who is lead author
of the study, recently published in the journal eLife.
In fact, in older people, they observed a decrease in right asymmetry, which indicates subtle changes
throughout the lifespan.

"We wanted to understand why the subtle differences between the left and right hemispheres are related to language and attention, and are associated with various developmental disorders," explains
Sofie Valk, who led the study and is in charge of MPI's CBS's Cognitive Neurogenetics Research Group.
"If we understand the heritability of this asymmetry, it will be the first step
in understanding the role of genetic and environmental factors in shaping this trait.
" We may eventually be able to figure out what went wrong
when the left-right difference was disturbed.
”

The researchers investigated the links using two databases, one containing brain scans from humans, including twins, and the other containing brain scans
of 19 macaques.
By comparing identical twins, fraternal twins, and unrelated individuals, they were able to determine the differences between siblings, and therefore, what was determined not by genetics, but by environmental
influences.

In turn, through comparisons with macaques, where are the differences between humans and monkeys, and which ones were created
during evolution.
The scientists calculated these differences
using so-called low-dimensional functional brain connection tissue.
This reveals how well
different brain regions work together.
The researchers calculated this tissue feature for each brain hemisphere and then calculated the asymmetry index
by subtracting from left to right.

Reference: Heritability and cross-species comparisons of human cortical functional organization asymmetry