Classical conditioning of decreases in human systolic blood pressure.

Decrease in human systolic blood pressure of 4.35 mm Hg (range: 0 to 12 mm Hg) were classically conditioned in normal and hypertensive subjects using a delayed conditioning paradigm in which a 30-sec auditory stimulus (the conditioned stimulus) was followed immediately by tilting the subject 15degrees head-down to elicit small decreases in blood pressure. Conditioning occurred within five trials. A control group demonstrated that sensitization of the reflex by repeated tilting could not account for the blood-pressure decreases associated with the conditioned stimulus in experimental subjects.