Wondered Why People Are Left Or Right Handed? Not The Brain, But Spinal Cord Which Determines


Contrary to popular belief, the human brain is not responsible for determining whether a person is left or right handed, but it is in fact the spinal cord which holds the key.

The new finding comes courtesy a new study, which  was conducted by a team consisting of Judith Schmitz, Prof Dr H.C. Onur Gunturkun, headed by private lecturer Dr Sebastian Ocklenburg along with their colleagues from the Netherlands and South Africa.

These researchers demonstrated the scenario and shared that the gene activity in the spinal cord is asymmetrical even when the baby is inside the mother's womb. They revealed that a person's preference to either use the left or the right hand can be traced back to this asymmetry.

What Does The Study Say?

This research changes the understanding of the causes of hemispheric asymmetry. 

"Our findings suggest that molecular mechanisms for epigenetic regulation within the spinal cord constitute the starting point for handedness," said Ocklenburg from Ruhr University Bochum in Germany. 

Throughout the study, researchers analyzed the gene expression in the spinal cord, precisely noting that its segments are solely responsible for the arm or leg movements.

Several ultrasound scans were carried out previously, which suggested that after eight weeks of pregnancy the unborn child in the womb tends to prefer moving its right of left hand, whereas in the thirteenth week, they prefer sucking either their left or right thumb.

The spinal cord is responsible for translating the command received from the brain's motor cortex into a particular motion. The study shared that even before the connection between motor cortex and spinal cord, the left or right handedness of the child is established.

Therefore, the researchers believed that the left or right hand preference may have originated from the spinal cord, rather than in the brain.

Yet another finding from the study revealed the cause of asymmetric gene activity in children such as movements. The researchers noted that environmental influences are the root of it. These influences are responsible for affecting and minimizing the genes releasing enzymes, leading to the bond of methyl groups to the DNA.

These actions differ in both left and right spinal cord to a great extent, resulting in the different activity of genes.

The study has been successful in answering the tricky question of left- and right-handedness among people. Till date it was speculated that only the brain is responsible in determining the preference. However, the study has revealed that the spinal cord is indeed the one responsible.

The study has been published in the journal eLife.

Photo: Francois Schnell | Flickr

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