The analysis of the associative and non-associative hypothesis of the US-preexposure effect in preweanling rats

ARIAS, C; GAZTAÑAGA, M; CHOTRO, M. G.

Jaen

Congreso; Sociedad Española de Psicología comparada/International society for comparative psychology; 2012

Sociedad Española de Psicología comparada/International society for comparative psychology

The unconditioned stimulus preexposure effect (US-PE) is the attenuation of the acquisition of an aversion induced by a previously experienced US. Two main explanations have been proposed for this phenomenon: tolerance to the effects of the US (non-associative hypothesis) and contextual blocking (associative hypothesis). According to some authors, preweanling rats do not easily acquire contextual conditioning, which would predict a weak US-PE. However, recent evidences of strong US-PE in infant rats have been found. In this study a series of experiments test both, the associative and the non-associative hypotheses of US-PE in infant rats using taste aversion conditioning. Preweanling rats were preexposed to LiCl before conditioning of a flavor with this same US. Results show that: a) presentation of the US in the home cage or in a different context from conditioning does not affect the magnitude of the US-PE, b) non-reinforced exposure to the context after conditioning does not alter the expression of the US-PE, and c)preexposure to the US does not affect the strength of the hypothermic unconditioned response. These results do not support either of both main hypotheses (tolerance or contextual blocking) proposed to account for the USPE in rats. (Basque Government IT-276-07, Ramon y Cajal contract to CAG).