Fig. 6: Tracing axonal segments.

a An example of an excitatory axon (orange) that has been traced in the stratum radiatum of the hippocampus (SR). This axonal segment establishes excitatory synapses (green) with six different dendrites (represented in different colors). b Proportions of excitatory (green) and inhibitory (red) axons in the SR, and layers 1 and 3 of the somatosensory cortex (L1 and L3, respectively). Asterisk: the differences between the SR and the other two locations were statistically significant (Chi-square; p < 0.05). c Distribution of synapses between dendritic spines and shafts. Excitatory synapses in the SR, L1 and L3 have been broken down into those established on spines (dark green) and those established on dendritic shafts (light green). Inhibitory synapses on spines (red) and on dendritic shafts (pink) have also been represented. See also Supplementary Tables S4, S5. Asterisks: Differences between the three brain regions were statistically significant (Chi-square; p < 0.001). d Linear densities of synapses established by excitatory (green) and inhibitory (red) axons in the SR, L1 and L3. See also Supplementary Table S6. Asterisk: the linear density of synapses established by excitatory axons in the SR is larger than in either of the other two regions (KW, Bonferroni correction; p < 0.001). Double asterisk: differences between excitatory and inhibitory axons are statistically significant in L1 (MW, p < 0.001).