Initiation and inhibitory control of saccades with the progression of Parkinson's disease - Changes in three major drives converging on the superior colliculus

► Three major drives converge on the superior colliculus (SC) with disease progression. ► Two are inhibition from basal ganglia (BG) and decreased frontal cortex-BG activity. ► Finally, SC disinhibition emerge as functional compensation by extra-BG structures. ► Parameters reflecting SC disinhibition correlate negatively with some UPDRS subscores. ► We propose that saccades can gauge BG function in PD with disease progression.