The input mix in the Po neuropil varies across the nucleus. Idealized diagram of a coronal section of Po and VPM. The L6 and TRN inputs are both massive and homogeneously distributed across the two nuclei (thick gray arrows pointing from the outside to each nucleus). Vertical arrows indicating different Po portions represent other pathways whose prevalence in the local neuropil is markedly variable. Roughly estimated prevalence is indicated by different case size. An uneven pale red shading is used to note that the prevalence of L5b terminals (in red ink) varies widely across Po. Other glutamatergic (in black ink) and GABAergic (in blue ink) inputs are listed. In contrast with Po, the VPM neuropil input mix is dominated by trigeminal inputs. The camera lucida drawing of a typical mouse Po neuron (Porrero et al., 2016) is added for reference, at the same scale. Note that because of the size and radial arrangement of their dendrites, many Po cells might sample signals from adjacent input-specific domains. Scale bar: 250 µm. SCi: intermediate layers of the superior colliculus; Sp: spinal cord; DCN: dorsal column nuclei; APT: anterior pretectal nucleus; ZI: zona incerta; PrV: principal trigeminal nucleus; SpV: spinal trigeminal nucleus; PB: parabrachial nuclei.