Operant heart-rate conditioning in the curarised rat

Abstract

Many two-process learning theorists have attempted to separate the processes of operant and classical conditioning on the basis that the type of response each governed was typically different. Specifically, it has been postulated that responses of the autonomic nervous system are not subject to the direct influence of operant contingencies. Within a bidirectional experimental design, it was shown that both increases and decreases in heart-rate could be produced by operant training procedures. The considerably easier task of shaping increases in rate was attributed to the interaction of the schedule and the unconditioned effects of the reinforcer on heart-rate. However, the results of the training procedures on the heart-rate were shown not to be a direct consequence of the presentations of the reinforcer. In these studies curarised animals were used in order to rule out the possibility that the heart-rate changes were mediated by operant manipulations of overt and covert skeletal responses. Caution was stressed in the use of curariform drugs in studies of autonomic conditioning both because of their possible blocking action on autonomic ganglia and because of the difficulty in applying adequate and consistent artificial ventilation to the animal. Experimental attempts were made to determine the specific mechanisms responsible for the operant heart-rate changes which were obtained. The evidence implied that increased output from both the sympathetic cardiac nerves and the adrenal medulla were responsible for maintaining the increases in heart-rate. This evidence, together with the results of an experiment which showed depletion in levels of adrenal adrenaline as a consequence of the baseline procedures of curarisation and artificial ventilation, suggested that the procedures involved in these studies were stressful to the animal, producing increased sympathetic functioning .The difficulty in resolving the problem of whether operant and classical conditioning are separate processes was not resolved by these experiments because of the possibility of central nervous system responses being influenced by each type of conditioning. The implications of these studies interpretation of autonomic response changes is considerable and the probable importance of operant components in studies of classical conditioning were elaborated.