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From www.temporal-lobe.com
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Introduction
In order to comprehend the unique functional contribution of each parahippocampal - hippocampal sub-region, detailed anatomical knowledge is of pivotal importance. In the diagram featured on this website, the three-dimensional organization of the projection patterns between and within the parahippocampal region and hippocampal formation (see the anatomy primer) was visualized. All literature concerning projections of this system for the rat (see References) was collected and reported projections were stored in a database. Over the years, the nomenclature has changed and when necessary reported results were translated into a common frame of reference. Subsequently, almost 1600 projections were drawn between all subdivisions of the HF and PHR with as much topographical detail as current knowledge permits.
Many researchers that study the hippocampus have made their own attempt at drawing a diagram of the connections in the hippocampus. We - Natalie Cappaert and Niels van Strien - too started this project in an attempt to increase our own understanding of the network. Soon we discovered that creating a diagram of the hippocampal - parahippocampal connections with all its topological detail is a complex task. We started on this project in 2005 and worked together with an expert in the field, prof.dr. Menno P. Witter.
Although many additions are conceivable and in preparation See: Project Status, the first version of our interactive diagram is now freely available for download. It displays almost 1600 connections in the rat hippocampal - parahippocampal region, which can all be interactively switched on and off. In addition, a review is available in which underexposed aspects of the HF-PHR anatomy are highlighted together with some of the functional implications of these connections.
Below, an image of the diagram is displayed. Clicking on the image below will bring you to the download page.
Aims
Converging evidence suggests that encoding, consolidation and retrieval of declarative memories rely on interactions between the hippocampal formation and the parahippocampal region. Anatomical studies established that these areas consist of eight sub-regions, which form multiple, intricately connected networks. Current functional thinking does not fully take the improved under-standing of the circuitry into consideration. Here, we integrate existing knowledge into an interactive diagram in which any connection can be turned on or off at the level of cortical layers, which helps neuroscientists to conceive this complex network.
- To provide an overview of all known anatomical projections of the rat hippocampal - parahippocampal network.
- To provide a graphical interface with which users can turn on or off any connections at regional level down to the level of cortical layers.
- To make it easy to find references for a particular projection.
Status
- The diagram is now available as a supplement to our review of the parahippocampal - hippocampal anatomy in the April 2009 issue of Nature Reviews Neuroscience [1].
- Updated versions of the diagram will be offered for download through this website.
Currently, we are:
- Updating the website to a mediawiki environment, for ease of use. Only confirmed users will be able to make changes to this wiki. Should you want to add information to this website, please contact us.
- Adding anatomical connections of the amygdala with hippocampal and parahippocampal areas (in progress).
- Adding anatomical connections of the retrosplenial cortex with the hippocampal and parahippocampal areas (in progress).
- Adding anatomical connections of hippocampal - parahippocampal region and amaygdala of the mouse, monkey and human (in progress).
Future directions
- Add physiologically proven connections.
- Add contralateral projections.
Recognitions & Support
The project has been reviewed twice in the faculty 1000 Biology and received the following recognitions:
By Sachin Deshmukh and James Knierim [3]
The project behind www.temporal-lobe.com receives financial support from The Research Council of Norway.
References
- ↑ van Strien NM, Cappaert NL, Witter MP.The anatomy of memory: an interactive overview of the parahippocampal-hippocampal network. Nat Rev Neurosci. 2009 Apr;10(4):272-82
- ↑ Howard Eichenbaum: Faculty of 1000 Biology, 25 Mar 2009 http://f1000biology.com/article/id/1157623/evaluation
- ↑ James Knierim: Faculty of 1000 Biology, 7 Aug 2009 http://f1000biology.com/article/id/1157623/evaluation
