Input landscapes of the Po neuropil. Cartoon diagram of Po regions targeted by the various input systems. The approximate delineation of preferential input regions is based on the combined evidence from immunolabeling and tracing data. Higher color saturation is used to indicate regions containing more densely packed terminals. Empty areas indicate regions containing few or no terminals. a, Thalamic reticular nucleus (TRN) and L6 corticothalamic inputs cover Po in roughly homogeneous fashion. b, Cortical L5b inputs. c, Territories targeted by axons from dorsal column nuclei, the spinal cord, trigeminal complex or the intermediate/deep layers of the superior colliculus (SCi). d, Territories targeted by zona incerta and anterior pretectal nucleus.