The Brain’s Motor Cortex Is More Modular Than We Thought

For nearly a century, scientists have recognized that different regions of the brain’s cortex are responsible for controlling various body movements. This understanding dates back to the 1930s, when neurosurgeons used electrical stimulation to map how different cortical areas correspond to specific body parts. However, the precise organization of these motor control areas has remained an open question.

A new study from researchers at EPFL, the University of Cambridge, and Kumamoto University reveals that movement control in the brain is structured in a more modular and flexible manner than previously thought. By using advanced imaging and genetic tools, the researchers identified distinct neural modules within a single movement unit of the neocortex. These modules, located in different regions traditionally associated with planning, execution and sensory feedback, also change dynamically as an individual learns new motor skills.

The study, led by Keita Tamura, Pol Bech, and Carl Petersen at EPFL’s Brain Mind Institute, was published in Current Biology.

A horizontal network of movement control

To investigate how movements are controlled in the brain, the researchers used a combination of optogenetics – a technique that enables neural activity to be controlled with light – high-speed cortical imaging and machine learning-based movement tracking in mice. By selectively activating different types of neurons, they mapped how signals traveled through the brain to produce specific movements.

Their findings challenge the long-standing view that the cortex is primarily organized into vertical columns, where neurons are arranged in layers stacked from the surface to deeper regions of the brain. Instead, the study suggests a more horizontally distributed and modular organization of movement control.

The researchers found that within a broad cortical area responsible for mouth movements, different neuron types were not evenly distributed. Rather, they were localized into specialized sub-regions. These sub-regions form a horizontal network of functional modules, each contributing uniquely to movement planning, execution or sensory feedback.

The brain adapts by reorganizing its network

Further analysis revealed that these neural modules are not fixed. As mice learned new motor skills, some modules expanded into previously uninvolved cortical areas. This suggests that the brain refines motor control by rewiring connections between different neural modules, rather than simply improving the function of existing ones.

This adaptive reorganization could have implications for understanding how the brain recovers from injuries such as stroke. If some modules can compensate for lost function by forming new connections, future research could explore ways to enhance this process, potentially leading to improved rehabilitation strategies.

Implications for motor control research

These findings provide a new framework for studying how movements are controlled and learned at the level of brain networks. The modular and adaptable nature of motor control could help scientists refine models of movement disorders and recovery mechanisms.

By mapping how distinct neural modules interact, researchers may be able to develop more targeted interventions for conditions that affect motor function. Future studies could investigate whether similar modular principles apply to other areas of the cortex involved in cognition and sensory processing.

Reference: Tamura K, Bech P, Mizuno H, Veaute L, Crochet S, Petersen CCH. Cell-class-specific orofacial motor maps in mouse neocortex. Current Biology. doi: 10.1016/j.cub.2025.01.056

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