Functional imaging of the primate superior colliculus during saccades to visual targets.

The primate superior colliculus (SC) is a midbrain nucleus crucial for the control of rapid eye movements (saccades). Its neurons are topographically arranged over the rostrocaudal and mediolateral extent of its deeper layers so that saccade metrics (amplitude and direction) are coded in terms of the location of active neurons. We used the quantitative [14C]-deoxyglucose method to obtain a map of the two-dimensional pattern of activity throughout the SC of rhesus monkeys repeatedly executing visually guided saccades of the same amplitude and direction for the duration of the experiment. Increased metabolic activity was confined to a circumscribed region of the two-dimensional reconstructed map of the SC contralateral to the direction of the movement. The precise rostrocaudal and mediolateral location of the area activated depended on saccade metrics. Our data support the notion that the population of active SC cells remains stationary in collicular space during saccades.