The reasons for our left or right-handedness

February 17, 2017, Ruhr-Universitaet-Bochum
Judith Schmitz and Sebastian Ocklenburg are interested in right-left differences. Credit: Ruhr-Universitaet-Bochum

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 , 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 just as early as that.

The researchers, moreover, traced the cause of asymmetric . 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 , there is a difference to the activity of genes on both sides.

Explore further: Handedness arises from genes in the spinal cords of embryos

More information: Sebastian Ocklenburg et al. Epigenetic regulation of lateralized fetal spinal gene expression underlies hemispheric asymmetries, eLife (2017). DOI: 10.7554/eLife.22784

Related Stories

Handedness arises from genes in the spinal cords of embryos

February 7, 2017
The left side of the spinal cord matures slightly faster than the right side in human embryos of four to eight weeks age. This is the earliest left-right difference of development in the human nervous system yet discovered. ...

Fetal movement proven essential for neuron development in rats

November 15, 2016
A newborn rat's brain development stage is close to that of a human embryo in the second half of pregnancy, which allows suggests that similar movement patterns can help neuron development in humans. The research was published ...

Potential target for restoring ejaculation in men with spinal cord injuries or ejaculatory disorders

December 5, 2016
New research provides insights on how to restore the ability to ejaculate in men who are not able to do so.

Innovative imaging study shows that the spinal cord learns on its own

June 30, 2015
The spinal cord engages in its own learning of motor tasks independent of the brain, according to an innovative imaging study publishing on June 30th in Open Access journal PLOS Biology. The results of the study, conducted ...

Neuroscientific evidence that motivation promotes recovery after spinal cord injury

October 1, 2015
It is known by clinical experiences that motivation enhances patients' recovery from spinal cord injury or stroke. Depressive symptoms of the patients suffering from such brain injury could be a factor to delay functional ...

Health behaviors and management critical for spinal cord injury patients

August 11, 2016
It can happen in a split second from a vehicle crash, a fall or a gunshot: a person's spinal cord tissue is bruised or torn by a shocking blow.

Recommended for you

Aggression neurons identified

May 25, 2018
High activity in a relatively poorly studied group of brain cells can be linked to aggressive behaviour in mice, a new study from Karolinska Institutet in Sweden shows. Using optogenetic techniques, the researchers were able ...

The brain's frontal lobe could be involved in chronic pain, according to research

May 25, 2018
A University of Toronto scientist has discovered the brain's frontal lobe is involved in pain transmission to the spine. If his findings in animals bear out in people, the discovery could lead to a new class of non-addictive ...

Doctors fail to flag concussion patients for critical follow-up

May 25, 2018
As evidence builds of more long-term effects linked to concussion, a nationwide study led by scientists at UCSF and the University of Southern California has found that more than half of the patients seen at top-level trauma ...

Bursts of brain activity linked to memory reactivation

May 24, 2018
Leading theories propose that sleep presents an opportune time for important, new memories to become stabilized. And it's long been known which brain waves are produced during sleep. But in a new study, researchers set out ...

Study suggests brainwave link between disparate disorders

May 24, 2018
A brainwave abnormality could be a common link between Parkinson's disease, neuropathic pain, tinnitus and depression—a link that authors of a new study suggest could lead to treatment for all four conditions.

Researchers define molecular basis to explain link between a pregnant mother's nutrition and infant growth

May 24, 2018
For years, pregnant mothers have questioned their nutritional habits: "Will eating more cause my baby to be overweight?" Or, "I'm eating for two, so it won't hurt to have an extra serving, right?"

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.