Published online by Cambridge University Press: 13 July 2009
If information enters memory under the influence of a memory-enhancing substance, for about 16 hours thereafter the recollection of that information is no better than if it had been acquired without any treatment. Later tests of retention, however, performed one or more days, or even weeks, after the experience, show a drug-induced improvement of memory. Memory-enhancing compounds thus appear to facilitate the formation of the long-term memory trace. On the assumption that differences between treated and untreated animals emerge from that moment on when memory is based on the products of the processes modulated by the drugs, it can be postulated that long-term memory comes into play after about 16–20 hours.