Dorsoventral gradient of theta sweeps in medial entorhinal cortex

Abstract

During random foraging, the positional signal decoded from entorhinal grid cells exhibits left-right theta sweeps, alternating from one side of the heading direction to the other across successive theta cycles. Here, we report that theta sweeps are topographically organised along the dorsoventral axis of the medial entorhinal cortex, with the angular deviation from heading direction increasing gradually from dorsal (smaller scale) to ventral (larger scale) modules. This gradient coexists with a corresponding dorsoventral increase in angular deviation decoded from theta-modulated directional cells, which drive grid-cell theta sweeps. These phenomena parallel a broadening of head direction tuning and increasing occurrence of theta cycle skipping in single cell firing along the dorsoventral axis. Computational modelling demonstrates that these patterns are consistent with continuous attractor dynamics and a dorsoventral gradient in firing rate adaptation. These results highlight how theta sweeps can simultaneously represent multiple potential future locations and reveal a clear neural mechanism underlying this process.