Role of monkey superior colliculus in saccade averaging.

We have investigated the involvement of collicular movement cells in the monkey in the execution of averaging saccades, elicited by a visual double-step stimulus. We found that, qualitatively, most (12/14) movement cells were recruited during averaging saccades in roughly the same way as for comparable visually-elicited saccades to single targets (V-saccades). However, movement-cell responses during averaging saccades in trials where the target suddenly changed direction were often less intense than for a comparable V-saccade. In these cases, the averaging responses were observed to be also slower than V-saccades of the same amplitude. Firing rate and double-step saccade dynamics were found to be significantly correlated in 9/14 cells tested. Several hypotheses for the collicular role in the generation of averaging saccades are discussed.