Conditioned cardiac acceleration accompanying conditioned food reflex.

Abstract

A conditioned cardiac reflex accompanying conditioned food reflex was elaborated in dogs by applying the sound of metronome beat (conditioned stimulus) in combination with feeding of a definite amount of food (unconditioned stimulus), simultaneously or successively with an appropriate time interval. The changes of the cardiac rhythm were investigated, being recorded by means of “Cardiotachograph.” When the simultaneous conditioned reflex was well-established, the heart rate became accelerated by the conditioned stimulus approximately to the same extent as by the unconditioned stimulus alone. Both the generalization and the differentiation of the conditioned reflex were confirmed to exist quite in the manner consistent with the general principle known in the classical conditioned reflex. In the delayed conditioned food reflex, the cardiac rate increased soon after the onset of the conditioned stimulus similarly to the simultaneous conditioned reflex and decreased to a level somewhat higher than the basal cardiac rate after 20 to 30 seconds and remained at this level during the conditioned stimulus was being given. Thus there seems to be no internal inhibition for the conditioned cardiac acceleration corresponding to the inactive phase with respect to the salivary secretion in the delayed conditioned reflex. The mechanism concerned is not clear. After the delayed conditioned reflex had been well established, the conditioned cardiac acceleration was extinguished when the conditioned stimulus alone was repeatedly given without food. The conditioned cardiac acceleration, thus extinguished once, could be reestablished by renewed institution of reinforcements.