Hippocampal activity during classical discrimination—Reversal eyeblink conditioning in rabbits.

Multiple-unit neuronal recordings were taken from the hippocampi of 10 male, New Zealand white rabbits during classical discrimination and reversal eyeblink conditioning using 2 tones as the conditioned stimuli (CS+ and CS–) and an air-puff unconditioned stimulus. During discrimination training, characteristic learning-related activity was seen in the hippocampus on trials when a conditioned response (CR) was executed. During early phases of reversal training, however, when high numbers of CRs were evident to both the new CS+ (the former CS–) and the new CS– (the former CS+), no learning-related activity was observed. Characteristic CR-related hippocampal activity to the CS+ was observed only after the rabbits began to learn the reversal response. These results suggest that the hippocampus may encode different features of eyeblink conditioning during discrimination and reversal learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)