Dr. Daniel Reznik | Distinct Cortical Networks Associated with Subregions of the Human Medial Temporal Lobe Revealed by Intrinsic Functional Connectivity

The medial temporal lobe (MTL) consists of anatomically adjacent regions that follow the long axis of the parahippocampal gyrus and include the hippocampal formation, entorhinal, perirhinal, and parahippocampal cortices. Early neuropsychological studies in humans and lesion studies in animals suggested that the MTL is essential for memory function. However, the exact contribution of individual MTL subregions to mnemonic processing is unknown. Anatomical tracer studies in non-human primates examining connectivity of subregions within the MTL with the broader neocortex have been helpful in defining the structural boundaries within which memory-related functional mechanisms must operate. These studies suggest that the cortico-MTL circuitry in non-human primates is characterized by both parallel and hierarchical components that integrate diverse unimodal and polymodal informational sources. Similarly, human studies that used group-averaged intrinsic functional connectivity (FC) as an indirect measure of anatomical connectivity revealed distinct cortical networks associated with distinct subregions of the MTL. Nevertheless, important connectivity features expected from the non-human primate anatomy were not observed. Previous studies have demonstrated that network estimation based on group-averaged intrinsic FC can preclude the discovery of networks due to blurring between individuals' idiosyncratic anatomical features. Therefore, it is possible that important topographical details of the cortical networks linked to distinct subregions of the MTL are not fully revealed. In this talk I will present distinct cortical networks associated with distinct regions within the MTL estimated by intrinsic FC in densely sampled individuals. These networks will be discussed in terms of their relation to other distributed networks in human individuals and in terms of comparative neuroanatomy with other species.