Subcortical inputs to Po. Epifluorescence images showing retrogradely labeled cell bodies (arrows) in the ipsilateral reticular thalamic nucleus (TRN; a), zona incerta (ZI; b), anterior pretectal nucleus (APT; c), superior colliculus (SC; d), and contralateral principal (PrV; e, f) and interpolaris spinal (SpVI; g) trigeminal nuclei, gracilis nucleus (Gr; h), and dorsal horn of spinal cord (i). High-magnification details are shown as insets. A coronal section sketch is included, for reference. CuR: cuneatus nucleus, rotundus part; DMSpV: dorsomedial spinal trigeminal nucleus; DpG: deep gray layer; Gr: gracilis nucleus; InG: intermediate gray layer; InWh: intermediate white layer; Op: optic tract; PrV-DM: principal trigeminal nucleus, dorsomedial part; PrV-VL: principal trigeminal nucleus, ventrolateral part; ZId: dorsal zona incerta; Ziv: ventral zona incerta. Scale bars: 250 µm (a–i) and 25 µm (insets).