Scientists have understood that different parts of the brain’s cortex control different body movements for nearly a century. This foundational knowledge dates back to the 1930s, when neurosurgeons used electrical stimulation to map brain regions responsible for various body parts.
Recent research has delved deeper, exploring whether these regions can be broken down into smaller functional parts. While different types of neurons have been identified in the cortex, the intricate workings of these neurons in moving have remained unclear.
A groundbreaking study by EPFL, the University of Cambridge, and Kumamoto University has shed light on this complexity. The researchers employed advanced techniques to uncover distinct neural modules within the neocortex that govern movement. These modules are located in areas responsible for planning, executing, and sensing movements. Fascinatingly, these modules adapt as new skills are learned, offering fresh insights into motor control refinement.
The study, led by Keita Tamura, Pol Bech, and Carl Petersen at EPFL’s Brain Mind Institute and with contributions from Tamura at the University of Cambridge and Kumamoto University, was published in Current Biology.
The research involved studying movement control in mice using a combination of optogenetics (controlling neural activity with light), high-speed cortical imaging, and machine learning-based movement tracking. This approach allowed the team to activate different neuron types and observe the resulting brain activity that led to movements.
The researchers mapped the location of neurons controlling mouth movements to determine whether the broad movement control unit in the cortex could be divided into more minor elements. They then selectively stimulated various neuron types.
The findings were surprising: different neuron types controlled movement from distinct subregions within the broad movement unit rather than being evenly distributed. These subregions form a horizontal network of specialized modules, challenging the traditional view that the cortex operates in vertical columns, with neurons stacked vertically as processing units.
Instead, the study suggests a more horizontally interconnected system in which neuron-specific modules dynamically interact across different cortical regions.
Moreover, as mice learned new motor skills, some neural clusters expanded into other cortical areas. This indicates that learning involves rewiring connections between neural modules, allowing the brain to reorganize itself to optimize movement control.
This discovery holds significant implications for medical science. Understanding the structure of motor units and their adaptability could lead to better treatments for conditions like stroke or brain injuries. By revealing how neural networks compensate for loss of function in specific modules, scientists may develop more effective and targeted rehabilitation therapies, potentially restoring lost motor abilities.
In [summary](https://actu.epfl.ch/news/unraveling-the-brain-s-hidden-motor-modules/), this study offers a new framework for understanding how the brain controls and adapts motor functions, paving the way for advancements in neurological research and medical treatments.
**Journal Reference:**
1. Keita Tamura, Pol Bech, Hidenobu Mizuno, Léa Veaute, Sylvain Crochet, Carl C.H. Petersen. Cell class-specific orofacial motor maps in mouse neocortex. Current Biology 26 February 2025. DOI: [10.1016/j.cub.2025.01.056](https://doi.org/10.1016/j.cub.2025.01.056)