TIME-DEPENDENT CHANGES IN THE EFFECTIVENESS OF A NONCONTINGENT FOOTSHOCK REMINDER

To investigate the mechanism by which noncontingent reexposure to the UCS restores an extinguished fear response in rats, a noncontingent fo otshock reminder was administered to Sprague-Dawley rats at various in tervals after extinction of a fear response. Reexposure to the UCS res tored an extinguished fear response if the reminder was administered 7 days after extinction but not immediately or 24 h after extinction. A second experiment showed that in the 7-day condition prolonged exposu re to the situational cues following the noncontingent footshock atten uated recovery of fear. Results are discussed in terms of changes in t he discriminability of the training and reminder contexts as attribute s of stimuli are forgotten. (C) Academic Press, Inc.