Photostimulation of the STH neurons expressing ChR2 or HR under the Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) promoter did not ameliorate parkinsonism in a 6-OHDA model of rats, suggesting that both the facilitation and suppression of the STH firing do not have a direct effect on the amelioration of parkinsonism. Here, CA2 is linked to Parkinson disease.