Activity of omnipause neurons during “staircase saccades” elicited by persistent microstimulation of the superior colliculus

We have recorded the activity of omnipause neurons (OPNs) in the raphe interpositus during so-called staircase saccades produced by prolonged activation of the superior colliculus (SC) by microstimulation. By showing that OPNs cyclically pause during the periodic movements produced by the steady activation function, we reveal the functional relationship of the OPNs within the recurrent brainstem network that produces dynamic, closed-loop, and feedback control of saccades. Despite persistent, steady activation of the SC, the OPNs followed the periodic activity of the brainstem burst generator. This reveals a dominant influence of the oscillating brainstem circuit over descending control from the SC.