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The following papers exist for this project:

Abstract | Converging evidence suggests that each parahippocampal and hippocampal subregion contributes uniquely to the encoding, consolidation and retrieval of declarative memories, but their precise roles remain elusive. Current functional thinking does not fully incorporate the intricately connected networks that link these subregions, owing to their organizational complexity; however, such detailed anatomical knowledge is of pivotal importance for comprehending the unique functional contribution of each subregion. We have therefore developed an interactive diagram with the aim to display all of the currently known anatomical connections of the rat parahippocampal–hippocampal network. In this Review, we integrate the existing anatomical knowledge into a concise description of this network and discuss the functional implications of some relatively underexposed connections.

  • Sugar J, Witter MP, van Strien NM and Cappaert NLM (2011) The retrosplenial cortex: intrinsic connectivity and connections with the (para)hippocampal region in the rat. An interactive connectome. Front. Neuroinform. 5:7.

Abstract | A connectome is an indispensable tool for brain researchers, since it quickly provides comprehensive knowledge of the brain’s anatomical connections. Such knowledge lies at the basis of understanding network functions. Our first comprehensive and interactive account of brain connections comprised the rat hippocampal–parahippocampal network. We have now added all anatomical connections with the retrosplenial cortex (RSC) as well as the intrinsic connections of this region, because of the interesting functional overlap between these brain regions. The RSC is involved in a variety of cognitive tasks including memory, navigation, and prospective thinking, yet the exact role of the RSC and the functional differences between its subdivisions remain elusive. The connectome presented here may help to define this role by providing an unprecedented interactive and searchable overview of all connections within and between the rat RSC, parahippocampal region and hippocampal formation.

Abstract | The hippocampal formation and parahippocampal region are prominent components of the rat nervous system and play a crucial role in learning, memory, and spatial navigation. Many new details regarding the entorhinal cortex have been discovered since the previous edition, and the growing interest in the area of CA2 has been covered in this chapter. Emphasis is on a conceptual change: instead of perceiving the hippocampal circuit as the standard sequential processing network, current insights favor the concept that multiple parallel networks are present. Many new facts, combined with a thorough restructuring of information and inclusion of pointers to relevant (online) resources, make this chapter relevant to both the novice and senior readership.

 

  • F.Z.M. Binicewicz, N.M. van Strien, W.J. Wadman, M.P. van den Heuvel, N.L.M. Cappaert (2016) Graph analysis of the anatomical network organization of the hippocampal formation and parahippocampal region in the rat. Brain Structure Function;

Abstract | Graph theory was used to analyze the anatomical network of the rat hippocampal formation and the parahippocampal region (van Strien et al., Nat Rev Neurosci 10(4):272–282, 2009). For this analysis, the full network was decomposed along the three anatomical axes, resulting in three networks that describe the connectivity within the rostrocaudal, dorsoventral and laminar dimensions. The rostrocaudal network had a connection density of 12 % and a path length of 2.4. The dorsoventral network had a high cluster coefficient (0.53), a relatively high path length (1.62) and a rich club was identified. The modularity analysis revealed three modules in the dorsoventral network. The laminar network contained most information. The laminar dimension revealed a network with high clustering coefficient (0.47), a relatively high path length (2.11) and four significantly increased characteristic network building blocks (structural motifs). Thirteen rich club nodes were identified, almost all of them situated in the parahippocampal region. Six connector hubs were detected and all of them were located in the entorhinal cortex. Three large modules were revealed, indicating a close relationship between the perirhinal and postrhinal cortex as well as between the lateral and medial entorhinal cortex. These results confirmed the central position of the entorhinal cortex in the (para)hippocampal network and this possibly explains why pathology in this region has such profound impact on cognitive function, as seen in several brain diseases. The results also have implications for the idea of strict separation of the “spatial” and the “non-spatial” information stream into the hippocampus. This two-stream memory model suggests that the information influx from, respectively, the postrhinal–medial entorhinal cortex and the perirhinal–lateral entorhinal cortex is separate, but the current analysis shows that this apparent separation is not determined by anatomical constraints.

 

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