Human cortical areas activated in relation to vergence eye movements-a PET study

Human cortical areas activated in relation to vergence eye movements were determined using positron emission tomography. Binocular disparity-driven visual stimuli were presented using a head-mounted display. Eye movements were monitored continuously by an infrared limbus tracker. A combination of a bar and a cross was used as the target. In the vergence task, subjects were instructed to follow an approaching bar, while ignoring a stationary cross. Activation in relation to vergence eye movement was discriminated from activation in relation to motion vision by using the ignore-bar task as the control. In the ignore-bar task, subjects were instructed to fixate on a stationary cross, while ignoring an approaching bar. The fixation task was used as the basic control for both the vergence and the ignore-bar tasks. Areas of activation in relation to vergence eye movements were found in the bilateral temporooccipital junction, the left inferior parietal lobule, and the right fusiform gyrus by comparing regional cerebral flow between the vergence and ignore-bar tasks and by the conjunctive analyses of vergence-vs-ignore comparison with vergence-vs-fixation comparison.