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Cell Clue to Parkinson's

1 August 2023

Researchers in Denmark have made a discovery about what happens in the brain when we suddenly stop moving, providing valuable insight to help understand some of the mechanisms of Parkinson’s disease.

The study found a group of nerve cells in the midbrain which, when stimulated, stop all forms of motor activity, causing movement to pause or freeze. They even made the mice in the study slow down or completely stop breathing, and lowered their heart rate. 

As soon as the nerve cells were no longer activated, the mice would start the movement exactly where it stopped, as if pressing a play button. This pause-and-play pattern is unlike anything seen before and does not resemble other studies of motor arrest, where movement did not necessarily restart exactly where it had stopped. 

The nerve cells stimulated by the researchers are found in the midbrain in an area called the pedunculopontine nucleus (PPN). They differ from other nerve cells there by expressing a specific molecular marker called Chx10. The PPN is common to all vertebrates, including humans. So even though the study was performed in mice, the researchers expect the phenomenon to apply to humans too.

The study also compared this type of motor arrest to the freezing response caused by fear, and they were not identical. Researchers instead believe the response may be an expression of focused attention, similar to a hunting animal picking up the scent of prey, which can also happen in humans when concentrating on a challenging task.

The findings of the study may shed new light on understanding some of the mechanisms of Parkinson’s disease. Slow or arrested movement is one of the key symptoms of Parkinson’s, leading researchers to speculate that these special nerve cells in PPN are over-activated in people with the condition. If it was possible to find a way to reduce this reaction, it could help to alleviate problems with movement and body function.

Visit Parkinson's UK to learn more about the condition >

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