ONTOGENY OF EYEBLINK CONDITIONING IN THE RAT - AUDITORY FREQUENCY ANDDISCRIMINATION-LEARNING EFFECTS

The present study sought to determine whether acoustic properties of t he auditory conditioned stimulus (CS) or the use of a discrimination l earning procedure would alter the emergence of eyeblink conditioning b etween postnatal Days 17 and 24 (Days 17-24) in the rat. In Experiment 1, we employed a 3 x 2 x 2 factorial design, involving pitch of the a uditory CS (2.8, 5.0, and 9.0 kHz), training condition (paired vs. unp aired), and age (Days 17 or 24). Associative learning was evident at a ll tone frequencies on Day 24, but increased across frequencies on Day 17, although large age differences in conditioning remained at all to ne frequencies. In Experiment 2, rat pups were trained to discriminate 2.8 versus 9.0-kHz tones on Day 17 or Day 24. Eyeblink conditioning i ncreased with tone frequency on Day 24 but discriminative conditioning failed to appear on Day 17. These findings are discussed in relation to the role of auditory system maturation in the ontogeny of eyeblink conditioning. (C) 1995 John Wiley and Sons, Inc.