The prelimbic cortex contributes to the down-regulation of attention toward redundant cues

Previous research suggests disruption of activity in the prelimbic (PL) cortex produces deficits in tasks requiring preferential attention toward cues that are good predictors of an event. By manipulating cue predictive power, we clarify this role using Pavlovian conditioning. Experiment 1a showed pretraining excitotoxic lesions of the PL cortex disrupted the ability of animals to distribute attention across stimuli conditioned in compound. Experiment 1b demonstrated that these lesions did not affect the ability to block learning about a stimulus when it was presented simultaneously with another stimulus that was previously paired with the outcome. However, in a subsequent test, PL-lesioned animals learnt about this blocked cue faster than sham-lesioned animals when this stimulus alone was paired with reinforcement, suggesting these animals did not down-regulate attention toward the redundant cue during blocking. Experiment 2 tested this hypothesis using an unblocking procedure designed to explicitly reveal a down-regulation of attention during blocking. In this, sham-lesioned animals were shown to down-regulate attention during blocking. PL-lesioned animals did not exhibit this effect. We propose that observed deficits are the result of a specific deficit in down-regulating attention toward redundant cues, indicating the disruption of an attentional process described in Mackintosh's (Mackintosh NJ. 1975. Psychol Review. 82:276) attentional theory.