A dissociation between the proactive ECS effects on inhibitory avoidance learning and on classical fear conditioning

Abstract

This study investigated if the nature of the task is a determinant factor of whether or not a series of electroconvulsive shock (ECS) will proactively affect learning in animals. Rats were administered one daily ECS for 7 days. A day after the last administration they were concomitantly trained on an inhibitory avoidance task and on classical conditioning of fear response to a brief tone. Twenty-four hours later they were exposed for 8 min to an open-field arena and the freezing reaction was measured both before and after tone presentation (classical fear conditioning test). On the subsequent day the step-through latency (without presentation of the tone) was measured on the avoidance apparatus (inhibitory avoidance test). Impairment of inhibitory avoidance was seen in ECS-administered animals in comparison to controls, but the freezing reaction to the tone was equally high in both groups. Additional groups of rats were trained in order to control for ECS alone-induced freezing and pseudoconditioning. Also, it was demonstrated that the differential ECS effects on the two tasks were not due to the order of testing since similar dissociation was obtained when inhibitory avoidance test was conducted before the open-field test.