Researchers at St. Jude Children’s Research Hospital and Columbia University have discovered a previously unknown map within the mouse secondary motor cortex (M2) that organizes body movements.
Published in Nature Communications, the findings reveal how the brain coordinates distinct body regions during both rest and activity.
The team utilized high-speed optical brain imaging to observe neural activity. They identified that during periods of rest, specific sensory areas exhibited synchronized fluctuations in brain activity, each linked to a small, distinct region of the secondary motor cortex.
“Finding this map was unexpected,” said Elizabeth Hillman, chair of the St. Jude Department of Imaging Sciences. “We were initially looking for the primary brain regions that drive movement, but we noticed that during periods of rest, sensory areas had strong fluctuations in brain activity.”
The researchers confirmed that neuronal activity in these subregions depends on which body part is in use. While the secondary motor cortex engages transiently for simple movements, it sustains activity during more complex, coordinated tasks involving multiple body parts.
“All of these features explain why it has been so difficult to interpret motor cortex activity patterns during movements,” Hillman said. “Secondary motor cortex activity shifts between different states: from synchronized fluctuations during rest, to engaging transiently for simple movements, and sustaining during more complex movements involving multiple body parts.”
By analyzing these shifts, the researchers were able to interpret brain activity more effectively. Hillman compared the process to identifying individual instruments playing within an orchestra.
Hillman pioneered the wide-field optical mapping approach used in the study to produce real-time readouts of neural activity. Unlike traditional neuroscience studies that average multiple repetitions of a movement or focus on a single brain region, this method images activity continuously across the entire brain.
This approach revealed communication pathways between multiple regions that were previously hidden by older imaging techniques. The study suggests that these regions fluctuate together while at rest and become quiet once movement initiates.
The research team intends to use these high-speed imaging approaches to investigate how neurological diseases and brain injuries disrupt motor coordination. By visualizing how the brain controls movement in real-time, scientists aim to identify specific biomarkers and mechanisms of failure in the system.
Hillman expects to apply this imaging technique to evaluate potential therapies for various pediatric conditions. The goal is to better understand how diseases affect the brain’s ability to process behavior, movement, and cognition.
During rest, the secondary motor cortex exhibits synchronized fluctuations in activity linked to sensory areas. When movement begins, these regions become quiet, and the cortex engages to coordinate specific body parts.
Interpreting activity has been difficult because the secondary motor cortex shifts between different states, ranging from resting synchronization to transient or sustained engagement depending on the complexity of the movement being performed.
The wide-field optical mapping approach allows for continuous, real-time imaging across the entire brain rather than averaging multiple repetitions of a single movement. This provides a holistic view of communication pathways that were previously undetectable.
Related reading