Latent inhibition in the developing rat: an examination of context-specific effects

Dev Psychobiol. 2005 Jul;47(1):55-65. doi: 10.1002/dev.20074.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Association Learning / physiology*
  • Avoidance Learning / physiology
  • Conditioning, Classical / physiology*
  • Electroshock / methods
  • Freezing Reaction, Cataleptic / physiology
  • Inhibition, Psychological*
  • Male
  • Odorants
  • Rats
  • Rats, Sprague-Dawley
  • Retention, Psychology / physiology