In addition, several web-based atlas resources, both two- and three-dimensional, have been initiated, providing valuable additions to the conventional atlases ( Bai et al., 2006 Hjornevik et al., 2007 Lein et al., 2007 Jones et al., 2009). Textbooks and articles may provide more in-depth information on criteria used to subdivide the region, including cyto- and chemoarchitectonic features, but typically provide fewer illustrations ( Witter and Amaral, 2004 Andersen et al., 2007). The most commonly used atlases of the rodent brain provide annotated two-dimensional diagrams with boundaries and names of areas and regions, but with limited information about the criteria used to set the boundaries ( Swanson, 2004 Paxinos and Watson, 2007). To aid the identification of subdivisions and boundaries of the rat hippocampal region, several different atlases and textbooks are currently available. Hence, comparison of results across different studies, as well as analysis and planning of experiments require access to updated, detailed, and accurate definitions of the hippocampal subdivisions. Overall, this poses a challenge for communicating information about location in the region. The complexity increases over time, since anatomical and functional definitions of the rat hippocampal and parahippocampal regions and their subdivisions require more and more detailed descriptions, in view of for example complex functional gradients and increased usage in different ages of the experimental animals ( Petrovich et al., 2001 Hafting et al., 2005 Kjelstrup et al., 2008 Bast et al., 2009 van Strien et al., 2009 Boccara et al., 2010 Langston et al., 2010). Due to the anatomical complexity of this region and increased knowledge about its structure, chemoarchitecture, and connections, several schemes to subdivide the region have been introduced together with different nomenclatures (see e.g., Witter and Amaral, 2004 Andersen et al., 2007 Bota and Swanson, 2010). The rat hippocampal region is a frequently used research model for exploring both normal and pathological conditions, including the processes involved in memory and learning ( Kesner and Hopkins, 2006 Manns and Eichenbaum, 2009 Deshmukh et al., 2010) and neurodegenerative diseases ( de la Monte et al., 1988 Spargo et al., 1993 Shelbourne et al., 2007). In summary, we provide a novel content-rich digital atlas resource facilitating identification of morphological features relevant for delineating the anatomical subdivisions of the rat hippocampal region. Bi-directional links between images and the index of structures are provided. Images can be inspected with a graphical overlay of selected subregions.
#HIPPOCAMPUS ANATOMY AND FUNCTION RAT SERIES#
The atlas application consists of an interactive image viewer with high-resolution images of an extensive series of sections stained for NeuN, calbindin, and parvalbumin, and an index of structures with detailed descriptions of the criteria used to define the boundaries. To address this issue, we have developed a web-based atlas application in which images of histological sections are integrated with new and up-to-date criteria for subdividing the rat hippocampus formation, fasciola, and associated parahippocampal regions. An overview of both anatomical features and criteria used to delineate boundaries is required to assign location to experimental material from the hippocampal region. Published atlases of the rat brain typically lack the underlying histological criteria necessary to identify boundaries, and textbooks descriptions of the region are often inadequately illustrated and thus difficult to relate to experimental data. The region is complex, consisting of multiple subdivisions that are challenging to delineate anatomically. The rat hippocampal region is frequently studied in relation to learning and memory processes and brain diseases.
3 Department of Anatomy and Neuroscience, VU University Medical Center, Amsterdam, Netherlands.2 Centre for the Biology of Memory, The Kavli Institute for Systems Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway.1 Centre for Molecular Biology and Neuroscience, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.