Extinction in the developing ID rat: An examination of renewal effects

In the present series of experiments the context-specificity of extinction was examined from a developmental perspective. For postnatal day (PN) 23 rats, renewal offreezing to an aversive odor conditioned stimulus (CS) was observed when rats were conditioned in Context A, extinguished in Context B, and tested in Context A (i.e., ABA renewal). This effect was not observed in PN16 rats, which is consistent with previous studies suggesting that rats < similar to PN20 are impaired in encoding contextual information [i.e., Carew and Rudy [1991]. Developmental Psychobiology, 24, 191-2091. Subsequent experiments demonstrated thatfor rats conditioned at PN16 and tested at PN23, contextual regulation of extinction performance depended on the age at which extinction occurred. Specifically, ABA renewal was observed in rats given extinction training at PN22 but not in rats given extinction training at PN1 7. These latter results show that whether or not context regulates the expression of an ambiguous memory is determined by the animal's age when the memory becomes ambiguous. (c) 2007 Wiley Periodicals, Inc.