High resolution fMRI reveals distinct forms of associative novelty in the medial temporal lobe

Both Alzheimer’s Disease and Parkinson’s Disease involve alterations to the structure of the medial temporal lobe (MTL). Varying patterns of neuronal connectivity, however, suggest that not only does the MTL support learning and memory, but that its subregions play distinct roles in these processes as well. The exact nature of these contributions remains an area of active investigation. Examinations of associative novelty may offer an important tool for characterizing the processes carried out by different subregions. Associative novelty can be further broken down into associative novelty per se, which are simply novel stimulus configurations, and associative mismatch novelty, which are novel stimulus configurations that violate existing expectations. In this study, we used high resolution fMRI to characterize different associative novelty signals across the MTL; specifically, we were interested in whether there was a dissociation of associative novelty signal types between MTL subregions, or instead, a functional specialization for associative novelty signal types distributed across these subregions. Establishing subregional function could help elucidate the spectrum of cognitive deficits manifest in both Parkinson’s and Alzheimer’s patients.