Animal models of cognitive function

Various of animal models of cognitive function have been developed both to discover neural processes underlying cognition and to develop and test novel therapeutic interventions. Lesion models used in basic research have specified brain circuits involved in discrete cognitive behaviors, and simple system models have identified electrophysiological and biochemical events that might mediate processes such as learning and memory. Models used for drug screening for potential cognition enhancers have been less successful. Drug-screening models have identified several compounds as being of potential use as treatments for cognitive dysfunction prominent in conditions such as Alzheimer's disease. Unfortunately, most of these compounds have not been successful in clinical studies. This paper reviews representative model systems used for basic research and provides a more extensive treatment of models used to screen drugs, with an emphasis on models that attempt to mimic the cholinergic hypofunction characteristic of Alzheimer's disease. Included also are evaluations of the utility of models for drug screening and a discussion of possible reasons for discrepancies between preclinical and clinical evaluations of potential cognition enhancers.