Figure 2. Wiring diagram for cortical neurons including multisynaptic connections.

(a) Wiring diagram of 362 proofread layer 2/3 (L2/3) pyramidal cells (PyCs) as a directed graph. Two orthogonal views with nodes at 3D locations of cell bodies. Single (gray), dual (blue), and triple, quadruple, quintuple (red) connections. (b) Dual connection from a presynaptic cell (orange) to a postsynaptic cell (gray). Ultrastructure of both synapses can be seen in closeups from the electron microscopy (EM) images. The Euclidean distance between the synapses is 64.3 μm. (c) Normalized distributions of synapses sizes for L2/3 PyCs synapses separated by postsynaptic cell type. (d) Same as (c) for inhibitory cells in layer 2/3. (e) Cumulative distributions of the number of synapses per connection for different pre- and postsynaptic cell types. (f) Distribution of Euclidean distances between synapse pairs of dual connections. Median distance is 46.5 μm. Scale bars: 10 μm (a), 500 nm (b).

Figure 2—figure supplement 1. Renderings of all synapses from multisynaptic connections between layer 2/3 (L2/3) pyramidal cells.

Dendritic spines (yellow) and synaptic clefts (red) are rendered in 3D. Most are dual connections (160), but there are also triples (24), quadruples (3), and quintuples (2).

Figure 2—figure supplement 2. Examples of synapses between layer 2/3 (L2/3) pyramidal cells.

Scale bar: 500nm. In each pair of images, the left shows one section through a synapse, and the right adds the automatically detected cleft as an overlay. Note here that the clefts are associated with postsynaptic densities.