Be left-handed or right-handed, a matter of natural selection

26/06/2019

Each side of the brain has a specific function, and the human being is not alone in this asymmetry
ep / madrid 29.04.2017 | 15:24

Each side of the brain is specialized in one thing. GettyImages

Dextro-zurdo asymmetry is an invention of nature, which evolved to meet the specialization needs of many animals, mainly human beings. It is the conclusion of an article published this month in the magazine 'Neuron'.

"The study of asymmetry can provide the most basic plans of brain organization," says lead author of the work, Onur Güntürkün, from the Institute of Cognitive Neuroscience at Ruhr de Bochum University, Germany. "It gives us an unprecedented window in early brain wiring and the development that ultimately determines the destiny of the adult brain. Asymmetry is not limited to human brains, a number of animal models have emerged that can help unravel both the Genetic fundamentals as epigenetic for the phenomenon of lateralization. "

Güntürkün says that cerebral lateralization is used for three purposes. The first is the perceptive specialization: the more complex a task is, the more it helps to have a specialized area to perform that task. For example, in most people, the right side of the brain focuses on recognizing the faces, while the left side is responsible for identifying letters and words.

The next area is the motor specialization, which takes us to the left side. "What you do with your hands is a miracle of biological evolution," affirms. We are the masters of our hands and when channeling this training to a hemisphere of our brain, we can become more efficient in that type of dexterity. "

Natural selection probably provided an advantage that led to a part of the population, about 10 percent, favoring the opposite hand. What connects to both is the parallel processing, which allows us to do two things that use different parts of the brain at the same time.
Birds use each eye for a function

Cerebral asymmetry is present in many vertebrates and invertebrates. "It is, in fact, an invention of nature, which evolved because many animals have the same specialization needs as us", notes Güntürkün, who is also currently a visiting researcher at the Stellenbosch Institute for Advanced Studies in South Africa. Studies have shown that birds, such as chickens, use an eye to distinguish the grain from the ground stones, while at the same time with the other eye monitoring the predators above.

Research on pigeons has shown that this specialization is often a function of environmental influences. When a pigeon chick develops in the shell, her right eye turns to the outside, leaving her left eye to face her body. When the right eye is exposed to the light that enters through the shell, it triggers a series of neuronal changes that allow the two eyes, ultimately, to have different tasks.

A zebrafish modeling model has allowed researchers to study in depth the genetic aspects of asymmetrical development. Studies of important avenues of development, including the nodal signaling pathway, are revealing details about how, early in the development of an embryo, the cilia act by mixing gene products on one side of the brain or on the other. By manipulating genes in the nodal pathway and others, researchers can analyze the effects of these developmental changes on zebrafish behaviors.

Güntürkün believes that this research can provide information on the effects of asymmetry on brain diseases in humans. "There are hardly any disorders in the human brain that are not related to brain asymmetries," he says. "If we understand the ontogenesis of the lateralization, we can take a great leap to see how early brain wiring in the development process can go wrong in these pathological cases ".

Left-handed, the normality of difference