Discriminated instrumental learning by an acute encéphale isolé preparation

Rats were prepared and maintained with high cervical transections in order to study learning in an intact brain that is isolated from uncontrolled sensory input and immobilized, allowing ready access to central physiological mechanisms. Stimulation electrodes were aimed at loci associated with response reinforcing processes. A response sensor was placed in the mouth to record both learned and evoked biting. All experimental subjects were trained successfully to discriminate the presence of an exteroceptive stimulus that indicated availability of the brain stimulation for biting. An intact control subject performed similarly in a lever pressing situation for brain stimulation. Biting also was evoked in both experimental and control subjects following removal of reinforcers, in a relation like that previously demonstrated between withdrawal of reinforcers and attack. The value of the experimental procedure in the study of the neural bases of learning and of the interactions between learned and inherent response processes is discussed.