UCS intensity-dependent attenuation of infantile amnesia

Abstract

Unconditioned stimulus (UCS) reactivation treatments may attenuate infantile amnesia in rats by providing an external reminder cue, creating an internal contextual reminder cue via endogenous hormones, and/or modulating memory retrieval via neurochemical changes from activation of the stress cascade. In the present study, the UCS reactivation treatment and the relationship between intensity at training and intensity at testing were examined. In Experiment 1, 17-day-old Sprague-Dawley rats were given multiple-trial passive-avoidance conditioning with a high-intensity footshock. Those subjects administered a high-intensity reactivation treatment performed significantly better than did subjects that received a low-intensity reactivation treatment, subjects that received no treatment, or pseudo-trained animals. Experiment 2 repeated the first experiment with a low-intensity training footshock. The results indicated that only a high-intensity reactivation treatment attenuated infantile amnesia. These findings suggest that the training UCS need not match the reactivation treatment in terms of intensity and leaves open the possibility that aversive reactivation treatments may be multifaceted, involving external contextual cues, internal contextual cues, and neuromodulatory effects from activation of the stress cascade.