The robust reciprocal connectivity with PER provides POR with access to information about individual objects,

and connections with other medial temporal structures also provide links to mnemonic input. Moreover, the PER is anatomically and functionally integrated with the amygdala, which is involved in emotion processing and reward learning (LeDoux, 2000; Pitkänen et al., 2000). The POR also receives very strong input from retrosplenial cortex and appears to rely on this information for contextual learning (Keene and Bucci, 2008; Robinson et al., 2012). Thus, the POR is optimally situated to combine object and pattern information from the PER with incoming contextual and spatial information from C646 ic50 retrosplenial and posterior parietal cortices to form complex representations of

specific environmental FK228 chemical structure contexts. The hippocampus is also implicated in contextual learning, so one question of interest is how the processing of contextual information differs between POR and the hippocampus proper. Results of experimental lesion studies of contextual fear conditioning suggest context is processed differently by hippocampus and POR. For example, posttraining lesions of the hippocampus are ineffective 50-100 days after training (Anagnostaras et al., 1999; Maren et al., 1997). In contrast, posttraining PER or POR lesions are effective even 100 days after training (Burwell et al., 2004). Object-location correlates similar to those described here in POR have been observed in the hippocampus. Komorowski et al. (2009)

reported that hippocampal cells signaled item-context conjunctions in a biconditional discrimination task in which the place determined which of two odor stimuli would be rewarded. In that study, item-location conjunctions developed over time as animals learned to associate items with reward. We have not examined the emergence of object-location conjunctions in the POR, but other work suggests that changes in the spatial layout of local stimuli result in immediate remapping in the POR (Burwell and Hafeman, 2003). The evidence suggests that POR supports online processing of context and provides representations of the current context to the hippocampus for the purposes of associative learning and episodic memory. This is consistent with the idea that the hippocampus Thalidomide is located above the PER and POR in a hierarchy of associativity (Lavenex and Amaral, 2000). We suggest that object information in the POR arrives by the well-documented direct PER to POR pathway. Alternatively, it could be that object information arrives at the POR by an indirect pathway that involves both the PER and the hippocampus. Indeed, the PER and POR each have reciprocal connections with the entorhinal cortex and CA1 of the hippocampus, and both project to the subiculum. This alternative view, however, does not account for the function of the direct PER-POR projections.