Interval between preexposure and test determines the magnitude of latent inhibition: Implications for an interference account

Abstract

The effect of a retention interval on latent inhibition was studied in three experiments by using rats and the conditioned taste-aversion procedure. In Experiment 1, we demonstrated an apparent loss oflatent inhibition (i.e., a strengthening of the aversion) in preexposed subjects that experienced a retention interval of 12 days between conditioning and the test. In Experiment 2, we found no effect of this retention interval on the habituation of neophobia produced by the phase of exposure to the flavor. In Experiment 3, we showed that interposing a retention interval between preexposure and conditioning produced effects exactly comparable to those seen in Experiment 1. The implications of these results for rival theories of latent inhibition, as an acquisition deficit or as a case of interference at retrieval, are discussed.

Interaction of retention interval with CS-preexposure and extinction treatments: Symmetry with respect to primacy

“…According to some theories of learning (e.g., Dickinson & Burke, 1996;Miller & Matzel, 1988), and supported by empirical results (e.g., Escobar, Arcediano, & Miller, 2002), extinguishing the training context should cause a recovery in responding to a target stimulus that was preexposed prior to conditioning (the opposite of an augmented CS-preexposure effect). Escobar et al's observation supports De la Casa and Lubow's explanation of the discrepancy between their result and the reports of recovery from the CS-preexposure effect (e.g., Aguado et al, 1994;Kraemer & Roberts, 1984).…”

“…Such results indicate that the expression of both first-and second-learned memories is subject to contextual modulation. The ubiquity of contextual modulation is important to consider when one is interpreting results from other experiments (e.g., Aguado et al, 1994) that show a recovery from the CS-preexposure effect when a delay is imposed between CS preexposure and training (as distinct from that between training and testing, which was the case in Experiments 1 and 2). If the first-learned memories of a CS were entirely context independent, then a shift in temporal context between CS preexposure and CS reinforcement should have no effect on the detection of the CS-preexposure effect.…”

“…In all, the effect is clearly replicable within their CTA preparation using their parameters. However, there are still a number of conflicting reports that suggest an opposite or null effect (e.g., Aguado et al, 1994;Kraemer & Ossenkopp, 1986). Toward reconciling the conflicting reports, De la Casa and Lubow (2000) provided evidence suggesting that the physical context of the retention interval plays a critical role in the occurrence of the augmented CS-preexposure effect.…”

“…However, when the CS is presented in a novel context (physical or temporal), there are fewer cues present to facilitate retrieval of either of the conflicting CS memories; therefore, responding will reflect the memories of the CS that are less reliant upon occasion setting by the context. In the aforementioned cases involving testing the effects of CS-preexposure (or extinction) treatment and conditioning after a shift in the temporal context (i.e., after a long retention interval; e.g., Aguado et al, 1994;Killcross et al, 1998;Kraemer et al, 1991;Kraemer & Roberts, 1984), responding to the CS is augmented, reflecting enhanced expression of the memory of the reinforced trials. These results suggest that the reinforced memories of the CS are more durable or less context specific than the nonreinforced memories.…”

“…In most CTA experiments, training and testing takes place in the home cages. Generally, in CTA studies, including those in which spontaneous recovery from the CS-preexposure effect has been observed in adult rats (e.g., Aguado et al, 1994), any retention interval also takes place in the home cage (i.e., the same context as training). De la Casa and Lubow found that, in their preparation, the augmented CS-preexposure effect occurs only when the retention interval is experienced outside of the experimental apparatus.…”