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Prof. Silvia Arber explains how neurons control our movements

All motor behaviors of the human body are controlled by neurons in the brain. Silvia Arber's team investigates how neurons build networks, how they control our movements, and why defects can lead to disruptions in movement processes.

How are our movements controlled?
The motor system spans the entire nervous system of our body. There are three types of networks that are interconnected and control our body movement. Firstly, there are the neuronal networks in the spinal cord. They are responsible for the execution of movements. The brain contains the networks responsible for planning movement. And finally, between the planning center in the brain and the execution networks in the spinal cord, is the center that selects which movement is performed. It is made up of regions located in the brainstem. All three networks together control our movements.

What do neurons look like?
Neurons are different from other cells in our body. They have long extensions, so-called axons, with which they carry information over long distances in our body. The ends of the axons meet receiving stations called dendrites at contact points called synapses. This enables neurons to transmit information to other neurons.

How exactly are our muscles set in motion?
In our spinal cord are so-called motor neurons, which tell our muscles to contract. Each motor neuron controls a muscle via a direct connection. The motor neurons themselves are organized in groups projecting to one muscle called pools. The individual movements are based on complex processes. When running, for example, signals are not only sent to the muscles in the legs but also simultaneously to the muscles in the opposite arm. This stabilizes the body while running and improves our balance. This alternating movement of arm and leg is similar in humans and many animal species.

What happens in a spinal cord injury?
In the case of a spinal cord injury, the flow of information from the brain to the spinal cord is interrupted at a certain point. So although the connections from the spinal cord to the muscle are still in place, movements can no longer be carried out because the commands from the brain do not reach the spinal cord.

Could we simulate such commands from the brain and artificially create the movement?
This requires an understanding of how the spinal cord receives its commands to move. In our research, we took a closer look at the communication between the brainstem and spinal cord in order to understand which neurons are responsible for which commands. It turns out that the neurons in the brainstem that give commands to the spinal cord networks are highly organized. Some regions in the brainstem are specifically occupied by neurons that are primarily connected to the networks for the arms, for example, and others that primarily control the networks controlling leg movements.

How can this knowledge be applied?
For example, in the treatment of Parkinson's. With so-called deep brain stimulation, it is already possible today to stimulate specific areas in the brainstem and thus specifically improve arm or leg movements. If we are able to better map the neural networks in the brainstem in the future, it might be possible to trigger such commands even more specifically and possibly even improve motor skills in spinal cord injuries.

Research Group Silvia Arber