Are we born or do we become right-handed or left-handed? It is said that between 85% and 90% of the world population corresponds to right-handed people; There are many interesting myths and questions about the laterality of people, many of these questions are being answered thanks to neurosciences, the understanding of hemispheric asymmetries has changed..
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Why is it that we are right-handed or left-handed? Laterality was long thought to be determined by the brain, however, asymmetry in spinal cord gene expression manifests itself from the first weeks of the baby's gestation in the mother's womb. A study carried out at the Ruhr University of Bochum, Germany by Sebastian Ocklenburg and collaborators from different countries (2017), found that the preference for using the right or left hand can originate in the spinal cord, they affirm that it is who determines whether we use one or the other hand more.
The researchers studied gene expression in the spinal cord between the eighth and twelfth week of gestation, they observed that in the eighth week, there were already marked differences in the left and right part of the spinal cord segments and what is it who transmits electrical impulses to control the movements of the upper and lower limbs (arms and legs) in the initial stages.
This activity takes place long before the part of the brain responsible for movement, the motor cortex, is "wired" to the spine. The asymmetry will define whether the person will be right-handed or left-handed between the eighth and ninth week of gestation in the mother's womb. Weeks later, the differences in each hemisphere in terms of shape and size also become visible..
Ocklenburg and his collaborators (2017) found that the spinal cord and the cerebral cortex are not communicated in such early stages of gestation, for which they concluded that laterality is determined directly by the spinal cord and not by the brain as previously thought. few years ago. Regarding hemispheric asymmetries, the data suggest a spinal, non-cortical onset, they stated.
They observed that movements are controlled by the spinal cord, which commands the cerebral cortex to execute a movement, while being able to detect certain environmental changes.
Epigenetics is a regulatory system that controls the expression of genes without affecting their composition, it corresponds to the study of interactions between genes and the environment in which they occur in organisms..
Some genes may or may not be expressed, this also depends on environmental influences, in the case of the spinal cord, these influences affect it in different ways. Genetic analysis showed that the left and right sides of the spinal cord develop at different rates. Although it is worth mentioning that genes can be only one component of laterality.
"Before the eighth week of gestation, the cerebral cortex and the spinal cord are not yet communicated, towards the ninth week of gestation and through the spinal cord it begins to have a predominance of a certain side".
A study by David Hecht (2013) found that left-handers could be more prone to depression and negative emotions, as they observed that the right brain of left-handers is activated more regularly and recently this has been associated with several characteristics of pessimistic people.
It may interest you: Characteristics of pessimists
Most right-handers process language in the left hemisphere, left-handers have a distribution of this ability in both hemispheres. What leads them to have more random and less specific skills, so if a left-handed person has a lesion in the left brain hemisphere, which is where language is processed, they tend to recover more quickly, since their processing skills of language are scattered in both hemispheres, having language skills distributed in both hemispheres makes the neural system more complex, which can increase susceptibility to anomalies and neurodevelopmental disorders, as pointed out by Daniel Geschwind, professor of psychiatry , Neurology and Human Genetics from University of California, Los Angeles, USA.
Increasingly specialized studies on human development from such early stages could help to identify new indicators that allow intervention in early stages and to try to compensate for any development problems as soon as possible.
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