Hippocampal unit response during temporal single alternation of classical conditioning with rewarding brain stimulation in the rat

Abstract

To evaluate hippocampal function on working memory, an experiment of rewarding classical conditioning with a temporal single-alternation (SA) paradigm was conducted. White rats that showed positive self-stimulation to the lateral hypothalamus were trained on an SA schedule with 60-sec intervals, in which reinforced trials (R; CS-US) were regularly alternated with non-reinforced trials (N; CS alone). Unit activity from the hippocampus and the animals’ movements were recorded during the pairing of auditory CS and lateral hypothalamic stimulation (US). When the experimental schedule was shifted to SA from pseudoconditioning, the hippocampal unit activity increased in the CS periods on both R and N trials in the absence of behavioral response alternation. During SA training, hippocampal unit activity in the CS period significantly increased on R trials relative to N trials, when a differential behavioral response also appeared. No detectable differences in the hippocampal unit background pre-CS levels were found between R and N trials. The results are discussed in terms of the interaction between working memory and reference memory in the hippocampal function. © 1985, Psychonomic Society, Inc.. All rights reserved.