The unconditioned stimulus preexposure effect in preweanling rats in taste aversion learning: lack of context dependence.

BOBBIO, A.; CARTELLO, S.; REVILLO, D.A.; ORELLANA, E.; SPEAR, N.E.; ARIAS, C.

Congreso; International Society for Developmental Psychobiology; 2011

The unconditioned stimulus preexposure effect (US-PE) refers to the interference paradigm in which the acquisition of the conditioned response is retarded due to the prior experience with the US. Most part of studies analyzing psychological mechanisms underlying this effect has been developed with adult rats. The most widely accepted hypothesis explains the US-PE as a contextual blocking effect. According to this hypothesis contextual cues block the conditioned stimulus (CS)-US association at conditioning. The modulatory role of the context in interference paradigms such as latent inhibition or extinction is not observable until PD23 in rats. In the present study we investigated in preweanling rats the US-PE by means of a taste aversion paradigm, and the context-dependence of such effect using a taste aversion preparation. Preexposure to LiCl before conditioning retarded the acquisition of taste aversion. This effect was unaffected by a shift in the context between preexposure and conditioning (Experiment 1). Additionally, the US-PE was still observable when the route of administration of the US was varied from preexposure to conditioning phases or when the injection cues were completely removed at conditioning (Experiment 2). Finally, signaling LiCl at preexposure by an odor did not attenuate the US-PE (Experiment 3). These experiments show a strong US-PE in preweanling rats, and suggest that this effect is not suitable of interpretation in terms of an associative learning in this ontogenetic stage.