Abrupt emergence of long-lasting memory in the pre-weanling rat

During the course of ontogenesis does long-lasting memory emerge progressively or abruptly, and when? To examine this question, rat pups were conditioned at different ages (3-, 10-, 12-, 15- or 18-day-old) and tested at different retention intervals: from 3 days to 1 year. Conditioned aversion memory established before 12-day-old lasts for only 1 week, but when acquired after 15 days, memory survives for more than 1 year. This defines a short temporal window of 3 days for sudden emergence of a remote memory. Our result offers a precise temporal target to explore the mechanisms involved in long maintenance of memory.