Generalization of the conditioned reflexes established by direct electrical stimulation of the hippocampus

In four dogs instrumental defensive conditioned reflexes to direct electrical stimulation of the hippocampus were elaborated. After reaching 60 percent CR performance, unreinforced stimulations of several limbic structures were given to test generalization. Positive generalization was more frequent than negative one. The generalization effect changed considerably in the course of further conditioning, during which two main types of changes were observed. After repeated stimulations of additional points in the hippocampus, the septum and the limbic cortex, a strengthening of the generalization effect was observed, while test stimulations of the amygdala and the hypothalamus resulted in a gradual decrease of the generalization effect, including its complete disappearance.