Health and Healthcare Systems

Left-handed? Right-handed? The difference isn't to do with your brain

Combination picture of a spine model, a spine model implanted with a traditionally used titanium tube, and a spine model implanted with a 3D-printed artificial axis (L-R), are displayed at Peking University Third Hospital in Beijing, August 14, 2014. Chinese doctor Liu Zhongjun has successfully implanted an artificial axis produced by a 3D printer into the spine of a bone cancer patient. This was the first time that an axis produced by 3D printing had been implanted into a patient, according to Liu. Normally, a diseased axis would be replaced by a standardised, hollow titanium tube, said Liu. Pictures taken August 14, 2014. REUTERS/Jason Lee (CHINA - Tags: SCIENCE TECHNOLOGY HEALTH) - RTR43AAP

It is not the brain that determines if people are right or left-handed, but the spinal cord. Image: REUTERS/Jason Lee

Julia Weiler
Deputy Editor in Chief, Rurh Universitat Bochum
Share:
Our Impact
What's the World Economic Forum doing to accelerate action on Health and Healthcare Systems?
The Big Picture
Explore and monitor how Neuroscience is affecting economies, industries and global issues
A hand holding a looking glass by a lake
Crowdsource Innovation
Get involved with our crowdsourced digital platform to deliver impact at scale
Stay up to date:

Neuroscience

Unlike hitherto assumed, the cause is not to be found in the brain.

It is not the brain that determines if people are right or left-handed, but the spinal cord. This has been inferred from the research results compiled by a team headed by private lecturer Dr Sebastian Ocklenburg, Judith Schmitz, and Prof Dr H. C. Onur Güntürkün. Together with colleagues from the Netherlands and from South Africa, the biopsychologists at Ruhr-Universität Bochum have demonstrated that gene activity in the spinal cord is asymmetrical already in the womb. A preference for the left or the right hand might be traced back to that asymmetry.

“These results fundamentally change our understanding of the cause of hemispheric asymmetries,” conclude the authors. The team report about their study in the journal “eLife”.

Preference in the womb

To date, it had been assumed that differences in gene activity of the right and left hemisphere might be responsible for a person’s handedness. A preference for moving the left or right hand develops in the womb from the eighth week of pregnancy, according to ultrasound scans carried out in the 1980s. From the 13th week of pregnancy, unborn children prefer to suck either their right or their left thumb.

Arm and hand movements are initiated via the motor cortex in the brain. It sends a corresponding signal to the spinal cord, which in turn translates the command into a motion. The motor cortex, however, is not connected to the spinal cord from the beginning. Even before the connection forms, precursors of handedness become apparent. This is why the researchers have assumed that the cause of right respective left preference must be rooted in the spinal cord rather than in the brain.

The influence of environmental factors

The researchers analysed the gene expression in the spinal cord during the eighth to twelfth week of pregnancy and detected marked right-left differences in the eighth week – in precisely those spinal cord segments that control the movements of arms and legs. Another study had shown that unborn children carry out asymmetric hand movements just as early as that.

The researchers, moreover, traced the cause of asymmetric gene activity. Epigenetic factors appear to be at the root of it, reflecting environmental influences. Those influences might, for example, lead to enzymes bonding methyl groups to the DNA, which in turn would affect and minimise the reading of genes. As this occurs to a different extent in the left and the right spinal cord, there is a difference to the activity of genes on both sides.

Don't miss any update on this topic

Create a free account and access your personalized content collection with our latest publications and analyses.

Sign up for free

License and Republishing

World Economic Forum articles may be republished in accordance with the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Public License, and in accordance with our Terms of Use.

The views expressed in this article are those of the author alone and not the World Economic Forum.

Share:
World Economic Forum logo
Global Agenda

The Agenda Weekly

A weekly update of the most important issues driving the global agenda

Subscribe today

You can unsubscribe at any time using the link in our emails. For more details, review our privacy policy.

The care economy is one of humanity's most valuable assets. Here's how we secure its future

Kim Piaget

May 21, 2024

About Us

Events

Media

Partners & Members

  • Join Us

Language Editions

Privacy Policy & Terms of Service

© 2024 World Economic Forum