Behavioral and pharmacological unravelling of memory formation.

A brief description of how a passive avoidance task, using one day-old chicks, has been used to test for memory formation is given. Chicks will peck at bright shiny beads but if a bead is painted with a bitter tasting chemical, after tasting it once, the chicks will refuse to peck on subsequent presentation of that bead. The chick associates the bitter taste with the particular characteristics of the bead. These experiments have led to the development of a model of memory. The basic model is made of short-term memory, which lasts 10 minutes, intermediate memory that has two phases A and B and lasts for 30 minutes and finally long-term memory. The use of certain classes of drugs to prolong, delay or abolish the various phases is described and then it is shown that many hormones and certain behavioral manipulations can modulate memory. Experiments are described which examine not only the temporal storage but delineate spatial storage within the brain. A brief discussion of current methodologies for looking at the exact spatial location of memory traces is given. The article concludes by emphasizing how even minor differences in protocols across laboratories can have large effects on the memory traces and stresses the significance of the narrow temporal windows, around the training trial, when memory can be modulated.