Abstract
Recent studies support the idea that stimulus processing in latent inhibition can vary during the course of preexposure. Controlled attentional mechanisms are said to be important in the early stages of preexposure, while in later stages animals adopt automatic processing of the stimulus to be used for conditioning. Given this distinction, it is possible that both types of processing are governed by different neural systems, affecting differentially the retrieval of information about the stimulus. In the present study we tested if a lesion to the dorso-lateral striatum or to the medial prefrontal cortex has a selective effect on exposure to the future conditioned stimulus (CS). With this aim, animals received different amounts of exposure to the future CS. The results showed that a lesion to the medial prefrontal cortex enhanced latent inhibition in animals receiving limited preexposure to the CS, but had no effect in animals receiving extended preexposure to the CS. The lesion of the dorso-lateral striatum produced a decrease in latent inhibition, but only in animals with an extended exposure to the future conditioned stimulus. These results suggest that the dorsal striatum and medial prefrontal cortex play essential roles in controlled and automatic processes. Automatic attentional processes appear to be impaired by a lesion to the dorso-lateral striatum and facilitated by a lesion to the prefrontal cortex.
Highlights
Latent inhibition (LI) is a retardation in the acquisition of a conditioned response during Pavlovian conditioning, if the conditioned stimulus (CS) has previously been presented on its own [1]
Simple main effect analysis revealed that the extended exposure groups consumed more liquid than the non-exposure groups in trials 2, 3, and 5 probably due to the preference of animals for sweet taste of saccharin
A mixed 2 x 2 x 2 ANOVA with trials as the within-subject factor revealed a significant preexposure x lesion interaction effect, F(1,31) = 5.99, p = 0.02, ηp2 = 0.145. This effect was due to the limited exposure mpfc group drank more liquid than non-exposure group (p = 0.019)
Summary
Latent inhibition (LI) is a retardation in the acquisition of a conditioned response during Pavlovian conditioning, if the CS has previously been presented on its own [1]. A variety of theoretical explanations have been offered for this effect. Some of these theories attribute LI to retrieval failure [2,3,4], other theories attribute it to acquisition failure [5,6,7,8]. With regard to the latter, it has been proposed on more than one occasion that the acquisition failure results from a loss of attention to the CS [9, 10].
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