Structural and functional map for forelimb movement phases between cortex and medulla

The cortex influences movement by widespread top-down projections to many nervous system regions. Skilled forelimb movements require brainstem circuitry in the medulla; however, the logic of cortical interac-tions with these neurons remains unexplored. Here, we reveal a fine-grained anatomical and functional map between anterior cortex (AC) and medulla in mice. Distinct cortical regions generate three-dimensional syn-aptic columns tiling the lateral medulla, topographically matching the dorso-ventral positions of postsynaptic neurons tuned to distinct forelimb action phases. Although medial AC (MAC) terminates ventrally and con-nects to forelimb-reaching-tuned neurons and its silencing impairs reaching, lateral AC (LAC) influences dorsally positioned neurons tuned to food handling, and its silencing impairs handling. Cortico-medullary neurons also extend collaterals to other subcortical structures through a segregated channel interaction logic. Our findings reveal a precise alignment between cortical location, its function, and specific forelimb -action-tuned medulla neurons, thereby clarifying interaction principles between these two key structures and beyond.

Automated summary

The study reveals the anatomical and functional connections between the cortical regions and medulla in mice, showing that distinct cortical regions generate synaptic columns in the lateral medulla that match the positions of postsynaptic neurons tuned to specific forelimb action phases. Additionally, cortical neurons extend collaterals to other subcortical structures through a segregated channel interaction logic. The findings clarify the interaction principles between the cortical and medulla structures.