Distinct familiarity-based response patterns for faces and buildings in perirhinal and parahippocampal cortex

An unresolved question in our understanding of the medial temporal lobes is how functional differences between structures pertaining to stimulus category relate to the distinction between item-based and contextually based recognition-memory processes. Specifically, it remains unclear whether perirhinal cortex (PrC) supports item-based familiarity signals for all stimulus categories or whether parahippocampal cortex (PhC) may also play a role for stimulus categories that are known to engage this structure in other task contexts. Here, we used multivoxel pattern analyses of fMRI data to compare patterns of activity in humans that are associated with the perceived familiarity of faces, buildings, and chairs. During scanning, participants judged the familiarity of previously studied and novel items from all three categories. Instances in which recognition was based on recollection were removed from all analyses. In right PrC, we found patterns of activity that distinguished familiar from novel faces. By contrast, in right PhC, we observed such patterns for buildings. Familiarity signals for chairs were present in both structures but shared little overlap with the patterns observed for faces and buildings on a more fine-grained scale. In the hippocampus, we found no evidence for familiarity signals for any object category. Our findings show that both PrC and PhC contribute to the assessment of item familiarity. They suggest that PhC does not only represent episodic context but can also represent item information for some object categories in recognition-memory decisions. In turn, our findings also indicate that the involvement of PrC in representing item familiarity is not ubiquitous.