How do mice remember routes? - briefly
Mice encode routes through hippocampal place cells that activate at distinct locations, supplemented by olfactory and tactile cues. This neural map allows rapid recall of the path during future navigation.
How do mice remember routes? - in detail
Mice navigate mazes and natural environments by encoding spatial information in several neural systems. The hippocampus contains place cells that fire when the animal occupies specific locations, creating a map of the environment. Grid cells in the entorhinal cortex generate a hexagonal lattice of firing fields, providing metric information that complements place cell activity. Head‑direction cells maintain a stable representation of the animal’s orientation relative to external cues.
Sensory inputs reinforce these internal maps. Visual landmarks produce consistent firing patterns in both place and grid cells, while olfactory cues contribute to route discrimination when vision is limited. Tactile information from whisker contact with walls and floors supplies additional positional data.
Memory formation involves synaptic plasticity. NMDA‑receptor‑dependent long‑term potentiation (LTP) in hippocampal circuits strengthens connections during repeated traversal of a path. Consolidation processes during slow‑wave sleep reorganize the encoded route into more stable representations, allowing recall after extended intervals.
Mice also employ path integration, continuously updating their position by summing self‑motion cues (proprioceptive and vestibular signals). This internal odometer works alongside external landmarks, enabling the animal to return to a starting point even when visual cues are absent.
Key mechanisms underlying route memory:
- Place‑cell firing fields anchored to specific locations.
- Grid‑cell periodicity providing distance metrics.
- Head‑direction signaling for orientation.
- Sensory cue integration (visual, olfactory, tactile).
- NMDA‑dependent LTP for synaptic strengthening.
- Sleep‑dependent consolidation of spatial traces.
- Path‑integration using self‑motion feedback.
Experimental evidence shows that lesions to the hippocampus or entorhinal cortex disrupt maze performance, while pharmacological blockade of NMDA receptors impairs acquisition of new routes. Optogenetic silencing of place cells during navigation leads to immediate loss of path fidelity, confirming their causal role.
Overall, mice retain routes through a distributed network that merges internal coordinate systems with external sensory information, reinforced by synaptic plasticity and consolidated during sleep. This architecture allows rapid learning of novel paths and reliable recall over long periods.