PAVLOVIAN AVERSIVE CONTEXT CONDITIONING USING CARBON-DIOXIDE AS THE UNCONDITIONAL STIMULUS

Four experiments were conducted to examine the utility of carbon dioxi de (CO2) as an aversive unconditioned stimulus (US) in a Pavlovian con text conditioning paradigm. Experiment 1 demonstrated that rats expose d to CO2 in a distinctive context showed elevated levels of freezing r elative to controls. Experiment 2 replicated this basic effect with a modified conditioning procedure and additionally demonstrated conditio ned analgesia. Experiment 3 demonstrated a positive monotonic relation ship between US duration and resistance to extinction of freezing beha vior as well as conditioned analgesia. Experiment 3 demonstrated extin ction and an extinction-related phenomenon, renewal. These studies cle arly demonstrate the utility of CO2, as a Pavlovian US.