GPI and Parkinson disease: The synergistic interaction between the STN and GPi has been known to affect gait (Singh et al., 2011a,2013; Singh, 2018), since increased STN firing is expected to enhance GPi activity, resulting in thalamic disfacilitation of the cortical region and, consequently, inhibition of motor performance in PD (Frank, 2006; Bogacz and Gurney, 2007; Zavala et al., 2015).