Scientists have discovered a group of nerve cells in the midbrain that, when stimulated, can halt all movement. These nerve cells, located in the pedunculopontine nucleus (PPN) and expressing a specific molecular marker called Chx10, have the ability to impact various forms of motor activity, including breathing and heart rate. This unique “pause-and-play pattern” of movement suspension does not appear to be related to fear, but rather may relate to a state of alertness or focused attention. The researchers believe that understanding these cells could provide insights into the motor symptoms associated with Parkinson’s disease.
The discovery of these nerve cells sheds light on what occurs in the brain when movement suddenly stops. When activated, these cells cause movement to pause or freeze, similar to setting a film on pause. Once the cells are deactivated, movement resumes from where it stopped, as if pressing “play” again. This pattern is distinct and unlike other forms of movement or motor arrest that have been studied before.
The nerve cells responsible for this phenomenon are located in the midbrain’s pedunculopontine nucleus (PPN) and differ from other nerve cells there by expressing the Chx10 marker. The PPN is found in all vertebrates, including humans, meaning that this discovery in mice may have implications for humans as well.
The researchers stress that this movement arrest is not related to fear, as it differs from the freezing response triggered by extreme fear. Instead, they believe it could be connected to attention or alertness, although further research is needed to confirm this hypothesis.
The study also has implications for understanding Parkinson’s disease. Motor arrest or slow movement is a common symptom of the disease, and the researchers speculate that over-activation of these special nerve cells in the PPN may inhibit movement. Therefore, understanding the fundamental mechanisms that control movement may eventually help uncover the cause of some motor symptoms in Parkinson’s disease.
Overall, this discovery of nerve cells that can suspend all movement may have significant implications for our understanding of motor control and various neurological conditions.