Scientists discover brain circuit that executes movement

A new study explored the part of the brain that responds to environmental triggers that cue planned movement.

The study, published in the journal, Cell, was conducted by scientists from several institutions including the Max Planck Florida Institute for Neuroscience, the Howard Hughes Medical Institute’s Janelia Research Campus, and the Allen Institute for Brain Science. To study what part of the brain initiates movement, scientists started by identifying the conductor of initiated movement within the neural circuit. To do so, researchers observed the neuron activity of mice during a cue-trigger movement task.

For this task, mice were trained to lick to the right of their mouth  when their whiskers were touched and to the left if their whiskers were not touched. The mice were trained to delay their movement until a specific noise was sounded. If the mice completed the correct movement after the cue, they were given a treat. The purpose of the experiment was for the mice to develop a plan of movement after their whiskers were touched and execute it only when they were triggered by the noise.

The study’s researchers found that the mice’ brain activity occurred from a circuit of neurons in their midbrain, thalamus, and cortex, immediately after the go cue as well as when the mice began the execution of their movement. Next, the researchers set out to discover whether the circuit functioned as a conductor using optogenetics, a technique that controls neuron activity using light.

"We have found a circuit that can change the activity of the motor cortex from motor planning to execution at the appropriate time,” said Hidehiko Inagaki, PhD, co-author of the study and researcher at Max Planck Institute for Neuroscience. “This gives us insight into how the brain orchestrates neuronal activity to produce complex behavior. Future work will focus on understanding how this circuit and others reorganize neuronal activity across many brain regions."

This study identified a neural circuit essential for the execution of movement in response to environmental cues. According to researchers, the study’s findings have clinical implications for motor disorders like Parkinson’s disease, where patients struggle to initiate movement on their own. Additional environmental cues, the study’s authors said, can help trigger more movement in patients with motor disorders. Identifying specific areas in the brain responsible for cued movement could help with future treatments for motor disorder, according to the authors.