BDNF and Parkinson disease: Preclinical studies indicate that VNS can enhance locomotor control, reduce neuroinflammation, increase brain-derived neurotrophic factor (BDNF), and mitigate neuronal damage in PD models (Farrand et al., 2017; Farrand et al., 2019; Kin et al., 2021; Hosomoto et al., 2023).