Latent Inhibition Is Facilitated When a Target Stimulus Is Preexposed in Compound With a Nontarget Stimulus, but Only When the Two Stimuli Coterminate: A Test of the Hall-Rodriguez Theory

The Hall-Rodriguez (Hall & Rodriguez, 2010) theory predicts that latent inhibition can be facilitated when a target stimulus is preexposed in compound with a second, nontarget stimulus: specifically, latent inhibition will be facilitated when the target coterminates with the second stimulus in preexposure, but facilitation will fail to occur when the two stimuli do not coterminate. The present study tested these predictions. In each experiment, rats were preexposed to a 30 s target stimulus alone or in compound with a second stimulus across its final 10 s, or they were preexposed to the context. All rats were then exposed to pairings of the target stimulus and foot shock, and finally, tested for freezing to the target. Experiment 1 demonstrated standard latent inhibition. Experiment 2 provided evidence that preexposure to a 30 s auditory target stimulus, in compound with a visual stimulus across its final 10 s, produced facilitated latent inhibition. Experiment 3 demonstrated that the latent inhibition was also facilitated when each 30 s presentation of a target visual stimulus was compounded with an auditory stimulus across its final 10 s. Experiment 4 showed that facilitation did not occur when each 30 s presentation of the target was compounded with a second stimulus across its initial 10 s, while Experiment 5 found that latent inhibition of the target was impaired when each of its 30 s presentations terminated in the onset of a second (10 s) stimulus. These findings are consistent with the predictions of the Hall-Rodriguez theory. They confirm that the facilitation of latent inhibition depends on coterminations of target and nontarget stimuli in preexposure and, more generally, that the impact of a second stimulus on latent inhibition to a target depends on their temporal relation in preexposure.