Enrichment-induced forgetting is associated with white matter microstructure in mice.

Memories are stored in brain circuits, sometimes referred to as engrams. Forgetting happens when these neural activity patterns fail to be reactivated by retrieval cues. Neuroplasticity can destabilize existing memory circuits by altering the fidelity of neural signals and contribute to forgetting. Existing research has described plasticity in grey matter that contributes to forgetting; however, plasticity within white matter has not been explored. Here, brain plasticity was induced after contextual fear conditioning by housing mice in environmentally-enriched multilevel cages (EE) for four weeks. EE mice demonstrated forgetting as measured by reduced time spent freezing during the fear conditioning test compared to mice housed in standard cages (SE) (EE