EFFECTS Of different initial eye positions on saccades evoked by elect
rical stimulation of the superior colliculus (SC) were investigated in
alert monkeys with the head restrained. The dependence of saccade vec
tor on initial eye position was studied quantitatively by multiple reg
ression analysis. Following stimulation at 240 of 367 sites in the SC,
saccade vector was influenced by initial eye position. The magnitude
of eye position effects on horizontal saccade component was similar to
that for vertical component. These effects were mostly found with sti
mulation in the caudal SC. Results suggest that eye position signals m
ay control excitability of neurones in the SC.