Additional Exposures Reverse the Latent Inhibitory Effects of Recent and Remote Exposures

We studied the learning produced by simple exposures to a stimulus. Exposures depressed orienting and subsequent conditioned freezing in rats. A remotely preexposed conditioned stimulus (CS) conditioned better and overshadowed a novel CS more than a recently preexposed CS. Additional preexposures reversed these effects: a remotely preexposed CS elicited more orienting, conditioned worse and overshadowed less than a recently preexposed CS. Exposure to a compound composed of a novel CS and a remotely preexposed CS resulted in the novel CS subsequently conditioning better than a novel CS exposed in compound with a recently preexposed CS. The results were interpreted to mean that stimulus-alone exposures produce a loss in associability which recovers across time, that this restoration deepens the loss in associability, and that this deepening is regulated by a common error term.