Saccade trajectories evoked by sequential and colliding stimulation of the monkey superior colliculus.

Using microstimulation we employed an explicit experimental control of activity in the superior colliculus at two sites within the motor map. We compared saccade metrics and dynamics evoked at each site independently with those caused by sequential presentation and collisions of the two stimulation trains. Essentially, we forced controlled spatio-temporal patterns of activity into the saccade control circuit with various timing relationships from known sites within the collicular motor map, thus revealing the spatio-temporal transformation from superior colliculus to eye movement dynamics under experimentally controlled conditions. We extend prior findings about decreasing time intervals between sequential presentations of stimulations to include mid-flight combinations and dynamic modifications of trajectory. We explore how asynchronous collisions between two movements systematically engage a normalization mechanism of movement metrics, and demonstrate how dynamic patterns of activity across the SC motor map can create mid-flight curvature of movement through the post-collicular dynamics of a displacement controller. The explicit control addresses feasibility for systems control models and provides benchmark data for experimental verification of model mechanisms.