Scientists Discover Hidden Body Movement Map in Mouse Brains Using Optical Imaging

“Finding this map was unexpected,” said Elizabeth Hillman, PhD, St. Jude Department of Imaging Sciences chair.

Scientists have uncovered a previously unknown map of body-part associations within the secondary motor cortex of the mouse brain, News-Medical reported. This discovery, published today in Nature Communications, reveals how specific regions within the M2 area correspond to different parts of the body.

The research team, composed of scientists from St. Jude Children’s Research Hospital and Columbia University, utilized high-speed optical brain imaging to identify these patterns. While researchers were originally searching for the primary brain regions that drive movement, they instead found a structured organization within the secondary motor cortex that had previously eluded detection.

The breakthrough began not during active movement, but during periods of rest. The researchers observed that sensory areas in the brain exhibited strong fluctuations in activity while the mice were still. According to the study, each sensory area’s resting activity was synchronized with a specific, small area of the secondary motor cortex (M2).

When the team fitted these individual M2 regions together, they formed a “neat little body-part map,” Hillman explained.

Mouse brain movement map discovery — Photo: UA.NEWS

By examining neuronal activity within these subregions, the scientists confirmed that activation was directly dependent on which part of the body was being used. This distinction provides a much clearer picture of how the brain orchestrates complex physical tasks.

“Once we figured out the pattern, activity became much easier to interpret. It was like recognizing which instruments were playing in the orchestra,” Hillman said.

The study also highlighted how the intensity of M2 involvement changes based on the difficulty of a task. For simple movements, the involvement of the secondary motor cortex is transient and short-lived. However, during complicated, coordinated movements that require multiple body parts to work in unison, the secondary motor cortex activates more strongly and sustains that activity for longer periods.

This shift in activity states—moving from synchronized fluctuations during rest to transient engagement for simple tasks and sustained activation for complex ones—explains why interpreting motor cortex patterns has historically been so difficult for neuroscientists.

The methodology used to find this map, a wide-field optical mapping approach pioneered by Hillman, allows for a holistic view of neural activity.

Unlike previous studies that often averaged multiple repetitions of a single movement or focused on isolated, tiny regions of the brain, this method provides real-time readouts across the entire brain during spontaneous movement. This continuous imaging revealed communication pathways between multiple regions that older approaches had effectively hidden.

The ability to visualize how the brain controls movement in real time offers a potential window into the mechanics of neurological failure. By understanding the “normal” map and its fluctuations, researchers can better analyze how and when these systems break down due to brain injury or disease.

Hillman intends to use these high-speed imaging approaches to investigate disease mechanisms and identify biomarkers. This work is particularly relevant for evaluating therapies for pediatric conditions that impact movement, cognition, and behavior. The research suggests that by seeing the system fail in real time, scientists can develop more targeted interventions for those suffering from motor disruptions.

“This study demonstrates that we can visualize how the brain controls movements in real-time, so we can also analyze how and when that system fails,” Hillman said.

The full findings of the study are available in the Nature Communications journal reference.

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