NOV 14, 2018 12:10 PM PST

Understanding Left-Right Dominance in the Brain

WRITTEN BY: Carmen Leitch

There are many common misconceptions about science, one of which is the belief that people can be characterized as either right- or left-brained. A 2014 study found that nearly 70 percent of teachers in the world think that students are either right- or left-brained, and it has an effect on how they learn. Modern neuroscience has found no evidence to support that claim. However, the hemispheres actually do specialize in different tasks (the video at the bottom of the article describes how the right-left brain misconception started). One hemisphere of the brain can also dominate the other side, and have an impact on how it responds. New research has investigated the mechanisms underlying that hemispheric dominance.

There seems to be no shortage of misconceptions about the brain and how it functions / Image credit: Maxpixel

Publishing in Cell Reports, biopsychologists from Ruhr-Universität Bochum used a pigeon model to demonstrate that small differences in reaction time form the basis for hemispheric dominance. This work may indicate that previous assumptions about hemispheric dominance aren’t painting the whole picture. It appears that reaction time is a significant factor. 

The researchers found that the neurons they were stimulating in their model reacted at the same rate in both hemispheres. The left hemisphere could trigger reactions faster, however. They also saw that more neurons were activated in the left hemisphere, and the neurons in the left hemisphere could actually alter the response in the right hemisphere (through a structure called the commissura anterior).

Thick bundles of nerve fibers called commissures connect the left and right sides of the brain. "In the past, it had been assumed that the dominant hemisphere transmits inhibitory signals to the other hemisphere via the commissures, thus suppressing specific functions in that region," explained Professor Onur Güntürkün. 

“The interactions occurring between the two hemispheres can be both excitatory and inhibitory. "This is why it has remained a mystery where, exactly, functional brain asymmetries stem from," noted Güntürkün.

For this study, the researchers used pigeons that they trained to differentiate between four colors. When the birds saw color, the scientists were able to record the neuronal activity in the birds’ visuomotoric forebrain, where information from visual stimuli is processed, and motor functions are coordinated based upon that visual input. In birds, these tasks are performed by the left hemisphere. 

Next, the researchers analyzed how the interaction between the hemispheres was influencing the process. The first author of the report Dr. Qian Xiao and Güntürkün intermittently blocked the activity of neurons that typically gather input from the other side of the brain. By monitoring the neuronal activity in the input-receiving neurons, they were able to learn more about how the two hemispheres interact.

They found that when both hemispheres can perform a task and compete for dominance, the left hemisphere can delay neuronal activity in the right hemisphere.

"The right hemisphere simply acts too late to control the response," explained  Güntürkün. "These results show that hemispheric dominance is based on a sophisticated mechanism. It does not hinge on one general inhibitory or excitatory influence; rather it is caused by minute temporal delays in the activity of nerve cells in the other hemisphere."

Get the lowdown on hemispheric dominance from the video above; learn what is fact, and what is a bit of fiction.


Sources: AAAS/Eurekalert! Via Ruhr-Universität Bochum, Nature Reviews Neuroscience, Cell Reports

About the Author
  • Experienced research scientist and technical expert with authorships on over 30 peer-reviewed publications, traveler to over 70 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
MAR 18, 2021
Microbiology
How to Avoid Greenwashing Your Lab
MAR 18, 2021
How to Avoid Greenwashing Your Lab
Greenwashing is a term used to describe an intentionally-misleading or false claim about the environmental benefits of a ...
MAR 25, 2021
Genetics & Genomics
Sperm's Molecular 'Memory' Is Revealed
MAR 25, 2021
Sperm's Molecular 'Memory' Is Revealed
The human genome contains the genes that make us who we are, because of how and when those genes are expressed. Gene exp ...
MAR 26, 2021
Cell & Molecular Biology
New 'Bio-ink' Gets 3D-Printed Organs Closer to Reality
MAR 26, 2021
New 'Bio-ink' Gets 3D-Printed Organs Closer to Reality
For the many people waiting for transplants, 3D-printed organs can't come soon enough. Researchers have been making stri ...
MAR 31, 2021
Microbiology
Deep-Sea Microbes Are 'Invisible' to the Human Immune System
MAR 31, 2021
Deep-Sea Microbes Are 'Invisible' to the Human Immune System
Scientists took an exploratory journey to a place in the central Pacific Ocean in Kirbati called the Phoenix Islands Pro ...
MAY 03, 2021
Health & Medicine
The Challenges and Advantages of Direct PCR Amplification
MAY 03, 2021
The Challenges and Advantages of Direct PCR Amplification
  Testing for COVID-19 continues to be one of the most important tools in the global fight to slow and reduce the i ...
MAY 15, 2021
Drug Discovery & Development
New Weight Loss Drug Converts Energy-Storing Fat into Energy-Burning Fat
MAY 15, 2021
New Weight Loss Drug Converts Energy-Storing Fat into Energy-Burning Fat
According to the World Health Organization (WHO), in 2016, around 2 billion adults around the world were overweight ...
Loading Comments...