SHORT-TERM, INTERMEDIATE-TERM, AND LONG-TERM MEMORIES

This paper focuses on the temporal dimension of memory formation and s torage. is the usual two-fold separation between short-term memory (ST M) and long-term memory (LTM) sufficient to encompass all the phenomen a of memory? The traditional view is that STM grades into LTM. Evidenc e for an intermediate-term memory (ITM) has been proposed by some inve stigators. We have used both rats and chicks to investigate the stages of memory formation. In this paper, the advantages of chicks for this type of research are briefly discussed. Using a paradigm that produce s weak training, the retention function for control chicks appears to be made up of four successive components which we have interpreted as representing the memory buffer, STM, ITM, and LTM. In experiments usin g a variety of kinase inhibitors, we have obtained evidence that ITM a nd LTM depend on different classes of protein kinase activities. Agent s that act on calcium/calmodulin kinase cause amnesia in the ITM range -15 to 30 min post-training. Another class of inhibitors act on one or more of the kinases PKA, PKC, or PKG and cause amnesia by 60 min post -training, so we interpret this group of inhibitors as inhibiting the formation of LTM. However, the three-stage model of memory may be over -simple. For example some agents including [Leu]enkephalin and MK801 c ause amnesia 4 or more h after training. It is suggested that there is a cascade of cellular events that underlies the formation of memory; these events extend from binding of neurotransmitters to receptor mole cules, to release of second messengers, through activation of protein kinases, to early intermediate genes, and protein synthesis. In the at tempt to diagnose and eventually ameliorate memory disorders, it may p rove useful to consider the possibility of an ITM stage in humans and to look for possible impairments of ITM in patients who suffer from me mory disorders.