a, Simultaneous unilateral injection (top) of AAV-DIO-ChR2 virus in the CnF (mCherry, red) and the PPN (eYFP, green) in Vglut2cre mice (N = 3). Sagittal view of the brain (bottom) displaying the location in the brainstem (1–4) and the spinal cord (5) of the coronal sections shown in c. b, Coronal section showing ipsilateral and contralateral projection areas from glutamatergic PPN neurons. c1–5, Schematics and coronal sections showing projection areas from glutamatergic PPN (left, green) and CnF (right, red) neurons onto nuclei in the pons, medulla and spinal cord. In the schematics, the darker shades delineate the areas with the highest density of projections. In coronal sections, labelled processes are seen in black. Anatomical landmarks are indicated in the schematics. Scale bars, 200 μm. 4V, fourth ventricle; 7N, facial motor nucleus; Gi, gigantocellular nucleus; GiA, gigantocellular reticular nucleus, alpha part; GiV, gigantocellular reticular nucleus, ventral part; IOM, inferior olive, medial nucleus; IRt, intermediate reticular nucleus; LC, locus coeruleus; LPGi, lateral paragigantocellular nucleus; LRt, lateral reticular nucleus; MdV, medullary reticular nucleus, ventral part; PnC, pontine reticular nucleus, caudal part; PnV, pontine reticular nucleus, ventral part; py, pyramidal tract; pyx, pyramidal decussation; RMg, raphe magnus; ROb, raphe obscurus; RPa, raphe pallidus. The mouse brain schematics in this figure have been reproduced with permission from Elsevier38.