Eye Movements and Reward, Sequential States, and Context-Dependent Target Selection

Abstract

The eye movement system is a complete sensorimotor loop from sensation to action, which includes a large number of distinct cortical and subcortical regions and participates in both reflexive and voluntary behaviors. This dissertation elucidates some of the functions of three cortical areas known to participate in eye movement behavior: the supplementary eye fields (SEF), motor area (SMA), and the lateral intraparietal area (LIP). In the course of executing eye movements, the eye movement circuitry interfaces with other functional circuits, including the networks of brain structures involved in reward processing, the temporal organization of behavior, target selection, and object perception. Here it is shown how LIP, SEF, and SMA participate in these multiple functional circuits, and complement each other during eye movement tasks. First, it is shown that neurons in the SMA carry a reward expectancy signal in the post-saccadic period of oculomotor tasks. Second, the neurons of SEF, but not LIP, are shown to collectively encode the temporal progression of the task. Third, in a target selection task, most LIP neurons are shown to respond to both cue and distractor stimuli, while most SEF neurons respond selectively only to the cue. Finally, fourth, the spatial tuning of parietal neurons is investigated in more natural circumstances, and the directional tuning preferences of cells in parietal cortex are found to be task dependent. These results extend the understanding of how these cortical brain areas that participate in eye movement behavior specialize and complement each other, and how they interface with other brain circuits, to support the organism in successfully completing a variety of instructed tasks.