Supplementary Figure 2: Single and compound connections on SR and SLM dendrites; related to Fig. 2.

(a) All reconstructed pyramidal cell dendritic segments from SR (top, n = 8) and SLM (bottom, n = 12). The dendritic cable is in gray, and dendritic spines from single connections are shaded orange while those from compound connections are blue and indicated by arrowheads. Note that axodendritic compound connections are not shown, and the dendritic branch may obscure some spines. (b) Density of compound synapses on reconstructed dendritic segments (from n = 8 SR segments and n = 12 SLM segments; ***two-sided Mann-Whitney test, p < 0.0001). (c) Distribution of axon path lengths (left) and angular trajectories (right) in SR (from n = 259 axons) and SLM (from n = 152 axons). Left inset, mean axon path length: **two-sided Mann-Whitney test, p = 0.003. Right inset, mean axon angular trajectory: **two-sided Mann-Whitney test, p = 0.002. (d) SLM path lengths (left) and angular trajectories (right) do not differ between axons making single (from n = 127 SLM axon segments) or compound connections (from n = 25 SLM axon segments). Left, mean path length: two-sided Mann-Whitney test, p = 0.67. Right, mean axon angular trajectory: two-sided Mann-Whitney test, p = 0.29. All box and whisker plots in (c) and (d) have the box depicting the 25th percentile, median, and 75th percentile, and the whiskers depicting 5-95 percentile. Data points outside these ranges are shown as individual circles. (e) Ultrastructural features of sets of coupled synaptic connections on SLM dendrites (from n = 72 compound connections, including the data from the axon-based dataset).