Importantly, when perception was studied with a protocol designed to minimize the influence of learning and memory, monkeys with perirhinal lesions performed normally, even on very difficult discriminations where the stimuli

were rotated, enlarged, shrunk, desaturated, or degraded by masks (Hampton and Murray, 2002). In the present study we developed a tactic to reduce the possible influence of learning and memory impairment on perceptual performance. Rather than buy Enzalutamide train animals to learn many discriminations and then present single probe trials for each discrimination (Hampton and Murray, 2002), we trained animals to learn a single discrimination and then, while maintaining a high level of performance, presented 150 probe trials at each of 14 different levels of feature ambiguity. We suggest that rats with perirhinal cortex lesions exhibited intact performance on every probe trial level because performance did not require any new learning. The GDC-0068 manufacturer basic discrimination was very well learned and performance remained high throughout testing. One study with rats deserves mention (Bartko et al., 2007). Lego blocks were used to construct sets of objects with different levels of feature overlap (four levels were used). By using an exploratory task in which rats prefer to explore the odd object in a group of three (with all objects available at the same time), rats

with perirhinal cortex lesions performed normally when the objects were most distinct Parvulin but were impaired when the objects had high degrees of feature overlap. Yet as noted previously (Suzuki, 2009), it is possible that rats must hold objects in memory as they move back and forth examining the different objects. In support of this idea, a related study found that rats with perirhinal lesions did exhibit impaired performance on this task but that rats with hippocampal lesions exhibited the same pattern of impairment (N.J. Broadbent et al., 2009, Soc. Neurosci., abstract). These findings raise the possibility that impaired

performance on this task might reflect impaired learning and memory rather than impaired perception. Studies with feature-ambiguous stimuli have also been carried out with patients who have medial temporal lobe damage that includes the perirhinal cortex (Lee et al., 2005, Barense et al., 2007 and Lee and Rudebeck, 2010). Yet attempts to replicate some of this work and to find impairments with new tests were not successful (Kim et al., 2011 and Shrager et al., 2006). We (Squire and Wixted, 2011) and others (Suzuki, 2009 and Suzuki, 2010) have suggested that patients with perirhinal damage who exhibit impaired performance on tasks of visual perception may have significant additional damage to the adjacent lateral temporal cortex. In summary, we have demonstrated that the capacity to resolve feature ambiguity can be systematically studied in the rat with considerable rigor.