Classical conditioning of total respiratory resistance in humans

A differential classical conditioning paradigm was used to investigate changes in total respiratory resistance in healthy adult female subjects. The conditioned stimuli were red and blue colors projected on a screen, and the unconditioned stimulus was an arithmetic task in which the subject mentally subtracted serial 17s from a number displayed on the screen. One of the two colors was paired with the arithmetic problem, and the other color was presented alone. Participants completed seven paired and seven unpaired trials. Both total respiratory resistance and functional residual capacity changes were measured before and during each conditioned stimulus. Total respiratory resistance was higher during the paired conditioned stimuli than it was during the unpaired conditioned stimuli. This result was not related to variations in functional residual capacity. It was concluded that elevated total respiratory resistance during the paired stimuli was a result of conditioning. The elevations were probably due to increases in bronchomotor tone. Conditioned changes in total respiratory resistance may be related to some respiratory behaviors both in healthy individuals and in patients with asthma.