Instrumental conditioning of the rat cardiac control systems.

The PR, PP, and RR intervals of the rat EKG were instrumentally conditioned using a variety of reinforcement schedules under computer control. The PR and PP intervals could be conditioned independently. Individual rats demonstrated either a steady shift of their response distribution or an abrupt change of an all-or-none variety. Some response distributions shifted continuously; others, through the growth of new response patterns in a manner reminiscent of hypothesis-testing behavior of human subjects. A study of the effects of single reinforcements showed that each reinforcement contributed to the learning behavior of the subject, in a well-defined but nonlinear fashion.