Perirhinal cortex inactivations produce recall deficits in fear extinction to a discontinuous visual stimulus

Several studies suggest that the perirhinal cortex (PER) may function to unitize stimulus components across time or modalities, and multiple findings have supported the involvement of the PER in stimulus unitization during fear conditioning. However, the role of the PER in processing such stimuli during other aspects of fear learning, including fear extinction, have not been evaluated. The current study assessed the involvement of the PER during a fear extinction paradigm using a discontinuous or a continuous conditioned stimulus (CS). Rats were randomly assigned to one of four groups based on two factors: CS type (a continuous light versus a discontinuous light) and PER manipulation (Saline group or Muscimol group). Results showed that the PER is involved in fear expression regardless of the CS type; however, the PER had a stimulus-specific role in the recall of an extinction memory.