Synaptic boutons, or simply, boutons, are enlargements of the axon, visible with light microscopy, that represent putative synaptic contacts. Bouton density is normally expressed as the number of boutons per 100 μm or per μm.
We collected and organized data on the local connectivity of pairs of pre- and postsynaptic morphological types (m-types). We used a subset of the data to constrain the connectome (the set of connections), namely bouton density and number of synapses per connection, and the rest to validate it.