The first axis runs from front to back (anterior to posterior). Regions at the front handle high-level motor planning and decision-making. Regions at the back connect tightly with sensory feedback, such as touch and proprioception — the body's sense of its own position in space.

The second axis runs from middle to side (medial to lateral). Along it, body representations shift systematically from the trunk and limbs toward the jaw, mouth, and face.

Triple-checked results

To confirm that the 16-region architecture reflects real biology rather than a statistical artifact, the team validated it with two independent methods: reconstructing the shapes of individual projecting neurons, and profiling the spatial distribution of different cortical cell types. All three approaches converged on the same 16-subregion layout.

"Understanding the precise wiring of the brain is essential for developing effective treatments for brain diseases," said Hongkui Zeng, Executive Vice President and Director of Brain Science at the Allen Institute and senior author of the study. "Here, our Swiss collaborators' expert charting of the functionally specific motor cortex circuit, combined with the Allen Institute's foundational connectivity atlas, resulted in such a precision map that drives movement control."

"The most fascinating finding is the extremely high precision with which the motor cortical modules interact with the output regions and that the modules communicate to the rest of the cortex using the same wiring logic," said lead author Silvia Arber, professor of neurobiology at the University of Basel and the Friedrich Miescher Institute.

Why it matters for ALS and FTD

The map has immediate medical relevance. Amyotrophic lateral sclerosis (ALS) selectively destroys upper and lower motor neurons, progressively cutting off signals to voluntary muscles. Frontotemporal dementia (FTD) targets frontal cortical circuits that govern behavior, personality, and language. One puzzle in both diseases: some motor cortical cells die early while their immediate neighbors survive.

With a 16-subregion map in hand, researchers can now pinpoint exactly which anatomical compartments harbor the vulnerable cells, and track how pathology spreads through connected output pathways. The findings in mice are preliminary in terms of clinical application — the work defines a framework for such studies rather than a treatment — but it gives the field a common reference to align data against.

The team has integrated the framework into BrainGlobe, an open-source computational tool, so that researchers worldwide can use it as a shared coordinate system, including for cross-species comparisons.

"Bringing together vast datasets describing the brain's wiring and its cellular makeup, we discovered a valuable and much more precise underlying blueprint of motor cortex organization," said co-first author Harsh Kanodia. Co-first author Antonio Falasconi added: "Researchers interested in the cortex now have an accessible unified map to align their data to, and this will accelerate progress in the field."

The study's authors include Antonio Falasconi, Harsh Kanodia, Nicholas Lusk, Shenqin Yao, Rui M. Costa, Hongkui Zeng, and Silvia Arber. The original research is open access.