Specific Nerve Cells in the Brain Can Completely Stop All Forms of Body Movements, Study Reveals

A team of researchers has discovered a behavior of neurons that adds new insight to our knowledge regarding the mechanism of the brain when a person stops moving.

Halting Movement Through Neuron Activation

Experts from the University of Copenhagen have found a group of neurons in the midbrain that can stop all movement when stimulated. These movements do not just refer to walking but to all forms of motor activity. In a clinical trial with mice, the research team was able to stop the animals' breathing or stimulate them to breathe more slowly and slow down their heart rate.

There are different ways to stop body movement. According to Professor Ole Kiehn, co-author of the study, what makes the discovered nerve cells special is their ability to make the motion get paused or frozen once they are activated.

The mechanism resembles a film set on pause where the actors' motion suddenly stops on the spot. When the scientists ended the activation on the nerve cells, the mice started their motion exactly where it stopped, like pressing the "play" button again.

The 'pause-and-play pattern' is unique in that it is unlike anything they have seen before. It is also not similar to other types of movement or motor activity that the scientists from the University of Copenhagen or another research team have investigated. As described by lead author Haizea Goñi-Erro, the movement they discovered does not necessarily start where it stopped, but it may begin again with a new pattern.

The neurons stimulated by the research team are located in the area of the brain called the pedunculopontine nucleus (PPN). They also differ from other nerve cells in the midbrain as they express a particular molecular marker known as Chx10. The PPN is commonly found in all vertebrates, including humans. This means that though the experiment was conducted in mice, the researchers are confident that this phenomenon can be applied to humans too.

Some people are familiar with the phenomenon of freezing triggered by extreme fear. Others might suggest that the neurons involved in this study are activated by fear, but that is not the case. Goñi-Erro and his colleagues theorize that this behavior expresses focused attention. However, they clarified that their research has not confirmed if that is the case, so more experiments are required.

The result of this study also sheds light on understanding some of the mechanisms of Parkinson's disease. Since it focused on the fundamental mechanisms involved in controlling the movement in the nervous system, it allowed the researchers to use optogenetics in stimulating the neurons present in the brainstem.

How Do Neurons Work?

Neurons, also called nerve cells, are the basic units of the brain and nervous systems' basic units, which send messages throughout the human body. They use electrical and chemical signals to help coordinate all the important functions of life.

Each neuron is connected to 1,000 other neurons, making a complex communication network. If a particular neuron receives many signals from other neurons, these inputs add up until they exceed a specific threshold. Once this threshold is exceeded, the neuron is prompted to send an impulse along its axon in a mechanism known as an action potential.