 Rats with a damaged perirhinal cortex seemed unable to tell novel objects from familiar ones—they were still more interested in exploring when novel objects were present, but examined the novel and familiar objects equally, unlike undamaged rats.Thus, other brain regions are capable of noticing unfamiliarity, but the perirhinal cortex is needed to associate the feeling with a specific source.The perirhinal cortex also receives a large dopaminergic input and signals the rewards that are associated with visual stimuli 

Damage to the perirhinal cortex has been shown to cause impairment in discriminating among object concepts when there is a high degree of visual semantic overlap among choices, such as between a hairdryer and a gun.