DYNAMICS OF RING AND TORUS MANIFOLDS IN DEVELOPMENT

Neurons in the medial entorhinal cortex (MEC) - grid cells and head-direction cells – encode an animal’s position and orientation respectively. These cells form internal maps with periodic topologies: grid cells are organized on toroidal manifolds while head-direction cells traverse ring-like manifolds. Using large-scale ensemble recordings in rat pups (from P8 to P19), we found that toroidal manifolds emerge in MEC subnetworks as early as postnatal day 10 (P10), preceding eye and ear opening, upright posture, and active exploration. Similarly, we detected clusters with HD-ring like topology as early as P9 in para-subiculum (PaS), a major input region to the MEC. Tori and rings in these network structures were coordinated as soon as they were recorded simultaneously (P10). Theta modulation of toroidal clusters arises only after eye opening, around P14. As pups began to explore actively around P15-16, the internally generated maps progressively aligned with external landmarks, culminating in stable spatial firing fields by three weeks of age. These results support the idea that even complex cognitive operations, such as spatial navigation, rely on preconfigured networks which subsequently anchor to the external world through experience-dependent plasticity.