RT Journal Article SR Electronic T1 Connectivity map of bipolar cells and photoreceptors in the mouse retina JF bioRxiv FD Cold Spring Harbor Laboratory SP 065722 DO 10.1101/065722 A1 Christian Behrens A1 Timm Schubert A1 Silke Haverkamp A1 Thomas Euler A1 Philipp Berens YR 2016 UL http://biorxiv.org/content/early/2016/07/26/065722.abstract AB Visual processing begins at the first synapse of the visual system. In the mouse retina, three different types of photoreceptors provide input to 14 bipolar cell (BC) types. Classically, most BC types are thought to contact all cones within their dendritic field; ON BCs would contact cones exclusively via so-called invaginating synapses, while OFF BCs would form basal synapses. By mining publically available electron microscopy data, we discovered interesting violations of these rules of outer retinal connectivity: ON BC type X contacted only ~20% of the cones in its dendritic field and made mostly atypical non-invaginating contacts. Types 5T, 5O and 8 also contacted fewer cones than expected. In addition, we found that rod BCs received input from cones, providing anatomical evidence that rod and cone pathways are interconnected in both directions. This suggests that the organization of the outer plexiform layer is more complex than classically thought.