Latent inhibition in the developing rat: an examination of context-specific effects.
Latent inhibition (LI) refers to the reduction in conditioned responding when the conditioned stimulus (CS) is preexposed prior to CS-unconditioned stimulus pairings. Experiment 1a demonstrated that preexposure to an odor CS prior to odor-shock pairings markedly reduced conditioned freezing in 25-day-old rats; however, this LI effect was observed only if odor preexposure and odor-shock pairings occurred in the same context (i.e., LI was context-specific at this age). The results of Experiment 1b showed that 18-day-olds also exhibited LI, but this effect was not context-specific at this age. In Experiment 2, rats were preexposed to the odor at 18 days of age and given odor-shock pairings at 25 days of age. These rats exhibited context-specific latent inhibition, suggesting that 18-day-old rats encoded the preexposure context. In Experiment 3, all parameters were identical to Experiment 2, with the exception that odor-shock pairings were given at approximately PN18 and testing occurred at approximately PN25. These rats exhibited latent inhibition at test, but this effect was not context-specific. The results of this study suggest that (a) PN18 rats can exhibit latent inhibition, and (b) the expression of context-specific latent inhibition depends on the age at which conditioning occurs.
Yap
Carol S L
CS
School of Psychology, University of New South Wales, Sydney 2052, Australia. c.yap@student.unsw.edu.au
Richardson
Rick
R
D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000502:physiology*; D001362:Avoidance Learning / Q000502:physiology; D003214:Conditioning, Classical / Q000502:physiology*; D004597:Electroshock / Q000379:methods; D046352:Freezing Reaction, Cataleptic / Q000502:physiology; D007266:Inhibition, Psychological; D008297:Male; D009812:Odorants; D051381:Rats; D017207:Rats, Sprague-Dawley; D012153:Retention, Psychology / Q000502:physiology