Experimental assessment of drug-induced changes in cognitive function: vasopressin as a case study.

Two important forms of cognition are knowledge about internal states and social cognition. Knowledge about internal states is dependent on the ability to discriminate between different classes of visceral sensations and to associate them specifically to distinctive cues. The phenomenon of conditioned taste aversion (CTA) is the best example of this type of knowledge. Many chemicals induce interoceptive changes that can be perceived by animals and give rise not only to subjective sensations but also to causal attributions. However, the possibility that animals are able to discriminate different forms of interoceptive changes in a CTA paradigm has received little attention. Studies of the mechanisms of vasopressin-induced CTA provide evidence that it is the case and that animals are able to classify in different categories sensations related to the vasopressor activity of vasopressin and sensation induced by a prototypical aversive drug, apomorphine. Social cognition involves what individuals know about each other. One of the requirements for social cognition is social recognition, i.e., the ability to identify other individuals and classify them in different categories. Social recognition can be assessed by changes in duration of investigation of another animal when the stimulus animal is presented at different intervals. This form of memory is based on olfactory characteristics of the stimulus animal in rats and it can be enhanced or attenuated by memory-modulating drugs, as demonstrated by experiments with vasopressin.