Representation of faces in perirhinal cortex

The prevailing view of medial temporal lobe (MTL) functioning holds that its structures are dedicated to long-term declarative memory. Recent evidence challenges this view, suggesting that perirhinal cortex (PrC), which interfaces the MTL with the ventral visual pathway, supports highly integrated object representations that contribute to both recognition memory and perceptual discrimination. Here, I used functional magnetic resonance imaging to examine PrC activity, as well as its broader functional connectivity, during perceptual and mnemonic tasks involving faces, a stimulus class proposed to rely on integrated representations for discrimination. In Chapter 2, I revealed that PrC involvement was related to task demands that emphasized face individuation. Discrimination under these conditions is proposed to benefit from the uniqueness afforded by highly-integrated stimulus representations. Multivariate partial least squares analyses revealed that PrC, the fusiform face area (FFA), and the amygdala were part of a pattern of regions exhibiting preferential activity for tasks emphasizing stimulus individuation. In Chapter 3, I provided evidence of resting-state connectivity between face-selective aspects of PrC, the FFA, and amygdala. These findings point to a privileged functional relationship between these regions, consistent with task-related co- recruitment revealed in Chapter 2. In addition, the strength of resting-state connectivity was related to behavioral performance on a face discrimination task. These results suggest a mechanism by which PrC may participate in the representation of faces. In Chapter 4, I examined PrC connectivity during task contexts. I provided evidence that distinctions between tasks emphasizing recognition memory and perceptual discrimination demands are better reflected in the connectivity of PrC with other regions in the brain, rather than in the presence or absence of PrC activity. Further, this functional connectivity was related to behavioral performance for the memory task. Together, these findings indicate that mnemonic demands are not the sole arbiter of PrC involvement, counter to the prevailing view of MTL functioning. Instead, they highlight the importance of connectivity-based approaches in elucidating the contributions of PrC, and point to a role of PrC in the representation of faces in a manner that can support memory and perception, and that may apply to other object categories more broadly