ONE-TRIAL AVERSIVE-CONDITIONING TO CONTEXTUAL CUES - EFFECTS OF TIME OF SHOCK PRESENTATION ON FREEZING DURING CONDITIONING AND TESTING

The present experiment examined the course of contextual freezing as a response to the delivery of a single electric footshock. In three groups of rats, the time of shock presentation was manipulated while the total amount of time spent in the shock context was equated among groups. One group received the shock early in the session, a second group was shocked in the middle of the session, and a third group received the shock at the end of the session. An additional control group was included that did not receive a shock. Relative to the early-shock group, the other two shock groups demonstrated a retarded onset of freezing after the shock delivery. During a subsequent nonshock test session, the pattern of freezing in the shock groups was indicative of one-trial temporal conditioning as a result of the previous conditioning session. Taken together, the results suggest that, within the range of the present parameters, manipulations of the time of a single shock presentation result in differences in freezing to contextual cues that are dependent on the presence of temporal cues.