Applying a combination of chemogenetics and optogenetics, they found that selective activation of caudal glutamatergic PPN neurons contributed to the relief of motor deficits in PD mice, and these effects were independent of CnF neurons (Masini and Kiehn, 2022), suggesting that more attention may need to be drawn to the caudal part of the PPN in relation to the PPN and PD treatment. This evidence concerns the gene NPHS1 and Parkinson disease.