Learning and Physiological Regulation

Within the cardiovascular system the baroreflexes of the carotid sinus and aortic arch are crucial to blood pressure stabilization. Our research focuses on the question of whether a mechanism of neural plasticity, known as classical conditioning, which is involved in drug tolerance, digestive secretion, and adjustment of critical visual tracking reflexes, is also involved in activation and calibration of the baroreflexes. Classical conditioning itself is simply a repeating sequence of a weak (conditioned) stimulus followed by a stronger (unconditioned) stimulus. It has been known since Pavlov that eventually, the weaker stimulus produces reflex effects closely resembling those of the stronger stimulus. Mathematical models that we have developed predict that classical conditioning can significantly augment the effectiveness of innate regulatory reflexes, and in various ways tailor their action to the needs of an individual's anatomy, constitution and life experience. Our recent research has established that the vascular sympathoinhibitory and cardiac depressor effects of the baroreflex can be conditioned, and that the conditioned responses satisfy the assumptions of the models. Our experiments all use a unique highly instrumented, CNS intact long-term rat model. We are able to monitor blood pressure, EKG, regional blood flow, brain electrical activity, electrical activity of individual skeletal and autonomic nerves, and many other physiological variables simulataneouly and accurately. At the same time we can present various visual and auditory stimuli, and activate selected autonomic afferent nerves repeatedly.

Ongoing studies will extend the empirical mechanisms and theoretical concepts of traditional physiology to include classical conditioning, and will specifically determine whether there is a fundamental and implicit role of conditioning in normal blood pressure regulation.