UC San Diego

Accurate action requires selectively processing only the sensory signals that are relevant to that action. The superior colliculus (SC) is important for the generation of saccadic eye movements, and has more recently been implicated in the winner-take-all selection of visual targets for voluntary eye movements and covert attention. However, there have been no conclusive tests of how important SC activity is for selecting visual objects as the targets of eye movements, or other actions. This dissertation reviews the role of the SC in eye movement and attention and then describes experiments that addressed three hypotheses: 1. that SC activity is important for the winner-take-all selection of visual targets for eye movements, 2. that the SC is important for the selection of visual targets for actions other than eye movements, and 3. that SC activity is important for integrating visual signals from potential targets, prior to the selection of a single target. The first two hypotheses were tested by experiments described in Chapter 2, in which the selection of visual targets for eye movements, or pressing a button, were compared before and after SC inactivation. Inactivation biased the subjects to select visual stimuli placed out of the affected visual field for each of the responses, but the effects on eye movements were much larger, indicating that the SC plays a particularly important role in the selection of visual targets for eye movement. The third hypothesis was tested by experiments described in Chapter 3, in which monkeys initiated smooth pursuit to multiple potential targets, prior to the selection of a single target. SC inactivation decreased the contribution of visual motion signals from potential targets within the affected visual field, and increased the contribution of motion out of the affected field, demonstrating that the SC plays a role in the integration of visual signals used to produce eye movements, prior to the selection of a single target. Together these results highlight the growing recognition that the primate SC is not just a motor map for saccades but plays a broader role in controlling selection for behavioral responses