Researchers find the ‘brain’s steering wheel’ in the brainstem of mice

This shows a brain
The neuronal networks that are directly responsible for coordination of the walking movement are located in the spinal cord and are relatively well described. Image is in the public domain.

Summary: Neural networks that are directly responsible for the coordination of walking movements are located in the spinal cord. A specific group of neurons in the brainstem signal to the spinal cord and control direction.

Source: University of Copenhagen

Walking is one of the most important motor skills for animals and humans. And for almost all people, being able to walk is deeply essential. In spite of this, researchers are still working to map out which signals and electrical impulses from the brain control our walking.

In a new study in mice, researchers from the Department of Neuroscience at the University of Copenhagen have come a little closer to understanding how the walking movement is controlled. They have mapped how certain neurons in the brain may be said to be the ‘brain’s steering wheel’ because they can control whether the mouse turns right or left.

‘It is an important discovery because movement is fundamentally one of the most basic features controlled by the brain. At the same time, motor disorders can be very disabling. Therefore, knowledge of the basic mechanisms of the brain and the spinal cord which control our movements is important’, says Professor Ole Kiehn.

The neuronal networks that are directly responsible for coordination of the walking movement are located in the spinal cord and are relatively well described. But researchers have now found that a particular group of neurons in the brainstem, which can be identified by their expression of a particular molecular marker called Chx10, signals to the spinal cord and controls the direction.

Credit: Professor Ole Kiehn.

‘The control is done by simply applying the ‘brake’ to the walking movment on the side that the mice turn to – then the muscles will contract on the same side. In this way, the length of the steps on one side becomes short and on the other side long, making the mouse turn. Thus, the Chx10 cells constitute a motor turning system – a kind of steering wheel’, explains first author of the study Jared Cregg, Postdoc at the Department of Neuroscience.

Funding: The study was supported by EMBO, European Research Council, the Novo Nordisk Foundation Laureate Programme and the Faculty of Health and Medical Sciences.

About this neuroscience research article

Source:
University of Copenhagen
Media Contacts:
Mathias Traczyk – University of Copenhagen
Image Source:
The image is in the public domain.

Original Research: Closed access
“Brainstem neurons that command mammalian locomotor asymmetries”. by Jared M. Cregg, Roberto Leiras, Alexia Montalant, Paulina Wanken, Ian R. Wickersham & Ole Kiehn.
Nature Neuroscience doi:10.1038/s41593-020-0633-7

Abstract

Brainstem neurons that command mammalian locomotor asymmetries

Descending command neurons instruct spinal networks to execute basic locomotor functions, such as gait and speed. The command functions for gait and speed are symmetric, implying that a separate unknown system directs asymmetric movements, including the ability to move left or right. In the present study, we report that Chx10-lineage reticulospinal neurons act to control the direction of locomotor movements in mammals. Chx10 neurons exhibit mainly ipsilateral projection, and their selective unilateral activation causes ipsilateral turning movements in freely moving mice. Unilateral inhibition of Chx10 neurons causes contralateral turning movements. Paired left–right motor recordings identified distinct mechanisms for directional movements mediated via limb and axial spinal circuits. Finally, we identify sensorimotor brain regions that project on to Chx10 reticulospinal neurons, and demonstrate that their unilateral activation can impart left–right directional commands. Together these data identify the descending motor system that commands left–right locomotor asymmetries in mammals.

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