Establishing a relationship between activity reduction in human perirhinal cortex and priming

Perirhinal neurons exhibit reduced firing rates with stimulus repetition, a phenomenon termed "repetition suppression." However, relationships between perirhinal repetition suppression and behavioral expressions of memory remain unclear. We used anatomically constrained functional magnetic resonance imaging (fMRI) to assess relationships between perirhinal activity and priming, a type of implicit memory. Priming was expressed as speeded animacy judgments for old versus new words. Concurrently, old words elicited less neural activity in bilateral perirhinal cortex. The magnitude of the left perirhinal activity reduction selectively predicted the magnitude of behavioral priming in an across-subjects hierarchical linear regression analysis. These findings have implications for considering how perirhinal cortex may contribute to different neurocognitive functions, possibly including both implicit memory and familiarity-based recognition. This study documents the first evidence linking behavioral measures of priming to information processing in perirhinal cortex.