THE ROLE OF SLEEP IN THE LONG-TERM CONSOLIDATION OF INFANT SPATIAL MEMORIES

Infantile amnesia refers to the inability of adults to retrieve memories formed early in life. However, accumulating evidence indicates that memories acquired during infancy can be retained in a latent form and later expressed in adulthood. Despite the well-established role of sleep in memory consolidation in adults, its contribution to the long-term persistence of infant memories remains unclear. Here, we investigated whether post-encoding sleep is required for the consolidation of remote spatial memories acquired during infancy. Male rats were trained in the object-place recognition (OPR) task at postnatal day 18–19. Memory expression was assessed either at recent time points (90 or 180 min after encoding) or remotely in adulthood (two months later). To examine the role of sleep, a separate group of animals underwent 90 min of sleep deprivation immediately after the encoding phase. Infant rats failed to express memory at recent time points, even when the post-encoding sleep opportunity was extended to three hours. In contrast, animals successfully retrieved the infant- acquired memory when tested in adulthood. Importantly, this remote memory expression was abolished when sleep was disrupted immediately after encoding during infancy. These findings suggest that spatial memories formed during infancy are stored in a latent state and that post-encoding sleep is necessary for their long-term consolidation, enabling later retrieval in adulthood. Our results highlight sleep as a critical determinant of infant memory persistence and provide new insights into the mechanisms underlying infantile amnesia.