Purpose of review
Classical conditioning is a form of associative learning, based on the pioneering work of I. P. Pavlov: due to its association with an unconditioned stimulus that induces an unconditioned response, an initially neutral stimulus will become a conditioned stimulus evoking a conditioned response in the absence of the unconditioned stimulus. One important area for the application of conditioning principles is the regulation of physiological systems in general, and endocrine responses and its concomitant changes specifically. Conditioned endocrine responses were predominantly addressed in animal studies so far, mainly examining conditioned insulin production (and blood-glucose change) and corticosterone release.
There are very few studies on classical conditioning of endocrine responses in the annual period of this review. The advancement, however, is that some are conducted with humans. Recently, as a new avenue, hormones and neurotransmitters have been examined as mediators of basic conditioning processes. Moreover, there is an increasing interest in gender-specific conditioning responses which are influenced by gonadal hormones.
Research on classical conditioning demonstrates that endocrine systems are adaptable to environmental signals. Likewise, the endocrine status of an organism (at least with regard to glucocorticoids and gonadal hormones) was shown to modify classically conditioned responses. Partly due to the high expenditure of conducting conditioning experiments, the quantity of studies is limited, but there is a need to extend this research to humans. In sum, the application of conditioning paradigms constitutes an important research tool for behavioral medicine as well as psychiatry to examine brain–behavior relationships.
Abbreviations ACTH: adrenocorticotropic hormone; CNS: central nervous system; CTA: conditioned taste aversion.