Short and long-term memory

It has been assumed for over a century that short-term memory (STM) processes are in charge of cognition while long-term memory (LTM) is being formed, a process that takes hours. A major question is whether STM is merely a step towards LTM, or a separate entity. The crucial experiments to answer this question were never done in mammalians. Here we demonstrated that that several treatments with specific molecular actions given into the hippocampus, entorhinal or parietal cortex immediately after one trial step-down inhibitory avoidance training can effectively block STM without affect LTM formation. This shows that STM and LTM involve separate mechanisms. Some treatments even affects STM and LTM in opposite directions. Others, however, influence both memory types similarly, suggesting links between the two both at a receptor level and the post-receptor level. Drugs effects on working memory (WM) were also studied. In some brain regions WM is affected by receptor blockers that alter either STM or LTM; in others it is not. Finally, behavioral observations have also separated STM from LTM. The former have no extinction; the later can be readily extinguished. STM is not sensitive to the deleterious effect of a novel experience presented 1 h after training; LTM certainly is. Thus, there are at least three simultaneous, related, but separate memory systems using simultaneously all or some of the same regions of brain; WM, STM and LTM.