Are you left handed? It's all about genes and brain asymmetry according to this new study

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Carlos Laforet Coll
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A new study has found that there is a genetic link between being left-handed and some asymmetries in the structure of the brain

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Why are some people left handed? It still remains a mystery, but new pieces are added periodically by scientific research. According to a new study, left-handed people show a shift to the right in brain asymmetry, and this link has a genetic origin.





You have surely noticed that left-handedness is rare (only 10% of the population has this characteristic). Science has not yet fully understood the causes but one thing is certain: manual skills, whether it is better on the left or on the right, does not derive directly from the hands. (Read also: Why are only 10% of us left handed? What science has discovered to date)

It is impossible to tell if a person is left-handed or right-handed simply by looking at their hands. In fact, there are no noticeable differences in the bones, muscles, tendons or other parts.

The fact of using one hand better than the other derives from the central nervous system, manual skill is in fact one of the many left-right functional differences that arise in the brain. In particular, in left-handers, the motor cortex in the right side of the brain (the left side of the body is controlled by the right side of the brain and vice versa) is dominant for fine motor behavior such as writing with a pen. Conversely, in right-handers, the left motor cortex is better at such tasks.

The new research adds an important detail to the knowledge already acquired. In fact, the link between left-handedness and asymmetries in the brain structure was studied, examining both the structural differences of the brain between left-handed and right-handed people and the genetic link between manual skills and brain structure.

To do this, the researchers analyzed brain imaging data of 28.802 right-handed and 3.062 left-handed people obtained from the British biobank. The UK Biobank is a large set of psychological and neuroimaging data obtained by volunteers in the UK, available to scientists around the world.

More specifically, the authors of the study analyzed the asymmetries in the structure of the brain (in all areas) as well as the genetic variation linked to manual skills and brain structure, then superimposing all the data. Considering the large sample used, the researchers are very confident in the results obtained.



What did they find? Left-handers showed a rightward shift in hemispheric structural asymmetries of the cortical surface in eight brain areas and a rightward shift in hemispheric structural asymmetries in cortical thickness in two brain areas. This suggests that left-handedness is associated with a shift of neuronal resources towards the motor dominant right hemisphere.

In a second step, the researchers investigated which genetic factors were linked to asymmetries in brain structure in areas that showed differences between left-handers and right-handers. They found that for two brain regions, the increased genetic disposition for left handedness was significantly associated with a rightward shift in brain asymmetries, suggesting a genetic link between left-handedness and asymmetries in the structure of the brain.

The study results have been published in Biorxiv but the research has yet to be peer-reviewed.

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Fonte: Biorxiv

Read also:

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