Published On: 25/06/2004|Categories: 2003–2007, Vol.25 (2), Vol.25 (2004)|

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An experiment is reported in which the effect of unconditioned stimulus (US) intensity on latent inhibition (LI) was examined, using a two-stage conditioned emotional response (CER) procedure in rats. A tone was used as the pre-exposed and conditioned stimulus (CS), and a foot-shock of either a low (0.3 mA) or high (0.7 mA) intensity was used as the US. A 2 x 2 factorial design was employed. The first factor was the pre-exposure condition (72 pre-exposures or non-pre-exposure) and the second was footshock intensity (low or high). A more durable LI effect was observed in the low-intensity condition than in the high-intensity condition during conditioning trials. The authors discuss the possibility that US intensity modulates either a process of restoring attention to the CS during conditioning or a contextual change, responsible for attenuating the LI effect in the high-intensity condition with respect to the low-intensity condition.

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