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Newly discovered brain cells have an important role in right and left turns

Researchers at the University of Copenhagen have discovered a network of neurons in the brain of mice that help them make right and left turns.

The researchers expect to find a similar right-left circuit in the human brain, and in the future, the discovery may be used in treatment for Parkinson’s disease.

The study has been published in the scientific journal Nature Neuroscience.

The brain steering wheel

The discovery was made by a research team consisting of Assistant Professor Jared Cregg, Professor Ole Kiehn, and their colleagues from the Department of Neuroscience at the University of Copenhagen.

In 2020,  Ole Kiehn, Jared Creeg and their colleagues identified the ‘brain’s steering wheel’ – a network of neurons in the lower part of the brainstem that commands right- and left- movements when walking. At the time, though, it was not clear to them how this right-left circuit is controlled by other parts of the brain, such as the basal ganglia.

“We have now discovered a new group of neurons in the brainstem which receives information directly from the basal ganglia and control the right-left circuit,” Ole Kiehn explains.

The basal ganglia

The basal ganglia are located deep within the brain, and years ago, scientists learned that by stimulating the basal ganglia you can affect right- and left-hand movements in mice. They just did not know how.

The newly discovered network of neurons is located in a part of the brainstem known as PnO. They are the ones that receive signals from the basal ganglia and adjust the step length as we make a turn, and which thus determine whether we move to the right or left.”

“When walking, you will shorten the step length of the right leg before making a right-hand turn and the left leg before making a left-hand turn. The newly discovered network of neurons is located in a part of the brainstem known as PnO (Pontine reticular nucleus, oral part). They are the ones that receive signals from the basal ganglia and adjust the step length as we make a turn, and which thus determine whether we move to the right or left,” Jared Cregg explains.

The study therefore provides a key to understanding how these absolutely essential movements are produced by the brain.

Parkinson’s disease

People with Parkinson’s have difficulties making right and left turns and these new findings may be used in treatment for Parkinson’s disease.

Parkinson’s disease is caused by a lack of dopamine in the brain. This affects the basal ganglia, and the researchers responsible for the new study believe that this leads to failure to activate the brainstem’s right-left circuit.

In the new study, the researchers have studied this in mice with symptoms resembling those of people with Parkinson’s disease. They made so-called Parkinson’s model, removing dopamine from the brain of mice and thus giving them motor symptoms similar to those experienced by people suffering from Parkinson’s disease

“These mice had difficulties turning, but by stimulating the PnO neurons we were able to alleviate turning difficulties.” Jared Cregg says.

Deep Brain Stimulation

Using Deep Brain Stimulation, scientists may eventually be able to develop similar stimulation for humans. At present, though, they are unable to stimulate human brain cells as accurately as in mice models, where they used advanced optogenetic techniques.

Read more about optogenetics: Making the invisible visible

Read more: Optogenetic therapy partially recovered visual function in a blind patient

“The neurons in the brainstem are a mess, and electric stimulation, which is the type of stimulation used in human Deep Brain Stimulation, cannot distinguish the cells from one another. However, our knowledge of the brain is constantly growing, and eventually we may be able to start considering focused Deep Brain Stimulation of humans,” Ole Kiehn concludes.

Photo: iStock

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