ONTOGENY OF EYEBLINK CONDITIONING IN THE RAT - EFFECTS OF US INTENSITY AND INTERSTIMULUS-INTERVAL ON DELAY CONDITIONING

Eyeblink conditioning in rat pups (17 or 24 days of age) was examined in two experiments, as a function of US intensity (Experiment 1) and i nterstimulus interval ([ISI] Experiment 2). In Experiment 1, pups rece ived three sessions of delay conditioning with a tone CS (380 msec, 2. 8 kHz, 90 dB [SPL]) and either a 1- or a 3-mA periocular shock US. Rat s trained on Day 24 showed conditioning that increased as a function o f US intensity. Pups trained on Day 17 did not condition with either U S intensity level. Experiment 2 examined the effects of conditioning w ith ISIs of 280, 560, 1,120, or 1,960 msec. Pups trained on PND24 show ed a decrement in acquisition with ISIs longer than 280 msec. Seventee n-day-old pups were not conditioned at any of the ISIs used. The resul ts indicate that the age-related development of eyeblink conditioning (Stanton, Freeman, & Skelton, 1992) is not altered under these paramet ric conditions.