Behavioral models of memory and amnesia.

In modelling memory and amnesia, the different forms of cognition must be distinguished. For memory, distinctions between acquisition, storage, and retrieval must be made and the different kinds of memory (e.g., immediate, working, reference) identified. Other notions, such as attention, orientation, and vigilance also belong under the heading "cognition". Thus the term "cognition enhancer" is imprecise because it does not indicate which kind of cognition is to be enhanced. Animal models should be developed for each type of cognition, be based on information from the clinic, and attempt to be specific. Examples of models more specific than the passive avoidance test were discussed and included the radial maze, in which different kinds of memory could be analyzed and correlated with, for example, changes in central cholinergic activity. From the point of view of drug development an important distinction was made between "empirical" and "simulation" models. In other areas of psychopharmacology "empirical" models have been widely used because they show predictable responses to known reference compounds. In the field of cognition there are no generally recognized reference compounds and therefore no "empirical" models. There is therefore a need for "simulation" models which imitate the various aspects of cognition and its pathology. The major criterion for validating this kind of model is that it should show changes similar to those observed in humans either resulting from a particular pathology or from a particular drug treatment.