Developmental enrichment enhances a topographically structured proprioceptive cortical code

The organization of proprioceptive cortex emerges from experience-dependent patterns of limb use during development, rather than merely reflecting peripheral innervation. However, the degree and specifics of these developmental changes remain poorly understood. To address this question, we investigated how early environmental enrichment (EE) reshapes the topography and functional properties of the mouse forelimb proprioceptive cortex. Using wide-field calcium imaging, we found that EE did not induce major reorganization of the mesoscale activation map. To resolve cellular level topology, we developed a large-field fluorescence macroscope enabling unbiased single neuron imaging across the entire activation area. We identified a topographically organized preference in directional tuning in which somatosensory and motor regions of the map encode distinct movement axes within the peripersonal space. Developmental enrichment reshaped this anisotropic representation at the cellular level. Rather than reducing the directional bias by homogenizing tuning across movement directions, EE strengthened the anisotropy by sharpening its topographic segregation and concentrating neuronal tuning around a common peripersonal axis. Our findings therefore reveal that enriched limb use and sensorimotor exploration reinforce an ecologically relevant specialization of the mouse proprioceptive cortex for movements directed toward the body.