Vying for dominance: dynamic interactions control visual fixation and saccadic initiation in the superior colliculus

Visual fixation and saccadic initiation are the tools that we use to explore the visual environment. In the superior colliculi, these behaviors may be viewed as independent motor programs that compete for control. Here, we provide a model describing the superior colliculi's involvement in visual fixation and saccadic initiation, in which extrinsic signals (sensory, motor, and cognitive) are shaped into competing motor programs through its local circuitry. In addition to providing evidence in support of this model, we demonstrate that it can explain the differences in the timing of saccadic initiation that have been observed experimentally.