Towards an interactive digital atlas system for exploring anatomical connectivity patterns in the entire rat brain

• ¹ University of Oslo, CMBN & IMB, Norway

Detailed knowledge about neuroanatomical projections and patterns of connectivity are essential for understanding brain function under normal and pathological conditions. Over the last century a tremendous amount of publications have reported neuronal connection data from the rat brain, which is a prevailing model in neuroscience research. Despite a rapid proliferation of anatomical data, we are still far from a comprehensive understanding of the wiring patterns of the brain. Retrieval of relevant information from legacy data is typically hampered by format and space restrictions in journal publications, and lack of standardized data presentations. Thus, there is a need for improved access to data describing precise neural connections.

To this end, we are developing database systems for organizing, sharing, and exploring neuronal connection data together with metadata describing the animal and experimental parameters required to reuse data. Building upon infrastructure and tools developed within the Rodent Brain Workbench portal (www.rbwb.org) we are currently developing a digital atlas system holding comprehensive series of high-resolution histological images from neural tracing experiments performed using standardized procedures. Recent progress in the project includes registration of more than 1200 images of coronal sections derived from six tract-tracing experiments in which a tracer was injected into stereotaxically defined body representations in the rat primary somatosensory cortex. The images are spatially organized according to assigned stereotaxic coordinates and can be inspected in an interactive web-based viewer tool. The distribution of tracer labeling has been manually evaluated and is communicated in a comprehensive table in which each region is directly linked to corresponding sections in the image archive.

The presented atlas system provides efficient access to a large number of detailed data on neuronal connections, potentially useful for a wide range of purposes, such as data mining for re-analysis, planning of new experiments, or interpretation of functional data involving the primary somatosensory cortex. The current pilot system serves to demonstrate proof of concept of how rat brain connectivity can be systematically mapped and communicated.