Characteristics of sound discrimination enhancement after sound exposure in adult rats.

The auditory perceptual capacity of adult rats was assessed with regard to performance during 2-sound-discriminative operant conditioning. If the animals were passively exposed to a sound stimulus before the conditioning, performance was improved (sound-exposure-enhanced discrimination [SED]). SED had a stimulus specificity that could not be predicted in terms of the cochleotopy. SED was obstructed by D-2-amino-5-phosphonovaleric acid, an antagonist of N-methyl-D-aspartate receptors, infused into the auditory cortex (AC). No evidence supported the hypothesis that SED was due to a change of attention or motivation or to interference in the association process (e.g., latent inhibition). These findings suggest that passive auditory experience can enhance the perceptual capacity of an adult rat's AC.