DISCUSSION
We have characterized the connectivity of a class of hyperexcitable excitatory pyramidal neurons existing within the superficial layers of the granular retrosplenial cortex. These neurons are excitatory (Figures 5, 6) and are the most prevalent cell type in this region (Figure 3), yet they make few local connections (Figure 6), instead sending their axons into the deeper layers and corpus callosum (Figure 7). However, they receive numerous inhibitory inputs from the neighboring FS cells (Figure 6) and thus are embedded within an inhibition-dominated network.