Abstract
Previous research suggests that the perirhinal cortex (PER), a hippocampal memory system structure, plays a role in fear learning when the conditioned stimulus requires unitization across time. This role of the PER appears to extend to extinction learning. However, how the PER may be involved in extinction learning has been less explored. Here, for the first time a chemogenetic approach is used to temporary silence the PER during extinction learning in male Sprague-Dawley rats during a Pavlovian fear extinction paradigm. Freezing, a measure of fear, was compared between an experimental group (PER silenced) and a control group (vehicle injected). Quantification of virus expression was similar across groups. Results show no significant group differences in cue-elicited freezing in any phase of the experiment, thus failing to support the stimulus unitization hypothesis. These results are discussed within the theoretical framework of the PER function and in consideration of the chemogenetic technique.