Activation of the medial entorhinal cortex drives memory-guided navigation behavior

The cognitive map in the medial entorhinal cortex (MEC) is essential for spatial memory and exhibits experience-dependent changes. Yet, it remains unclear whether MEC activation is sufficient to bias the network toward memory-guided navigation, precluding a causal link between the MEC and spatial memory. To address this gap, we examined and optogenetically manipulated MEC activity as mice navigated a virtual track for a water reward based on memory. During learning, spatial activity in the pre-reward region showed the highest consistency along the track and closely paralleled improvements in reward-predictive behaviors. This elevated pre-reward consistency was widespread across MEC neurons, rather than confined to a particular cell type, indicating a network-level representation supporting reward prediction. Strikingly, optogenetic activation of MEC at non-reward locations biased reward-predictive behaviors toward stimulation sites, but only when stimulation patterns were spatially consistent. Consistent stimulation also induced anticipatory reward-seeking before stimulation onset and this behavior gradually developed with repeated stimulation, reflecting memory formation for stimulation locations. Moreover, in animals that failed to learn the track well, consistent pre-reward activation, alone or combined with landmark activation, significantly enhanced their reward prediction. Thus, spatially consistent MEC activation underlies memory-guided reward prediction, supporting a causal role for the MEC in spatial memory.