Eye abduction reduces competition in the oculomotor system

Abstract

It is well established that there is a tight coupling between covert attention and the eye movement system. It is not yet clear whether there is a functional relationship between the two systems. Recent studies using the Posner cueing paradigm have demonstrated that preventing participants from executing a saccade reduces the attentional benefits associated with allocation of covert attention. One such technique involves abducting the eye in the orbit and presenting the stimuli outside of the effective oculomotor range (Craighero et al., 2004). In the present study we used saccadic curvature to examine whether eye abduction also reduces the competition in the oculomotor system. Saccadic curvature arises from competition within the oculomotor map when a visual distractor competes with the target. Typically, this causes saccades to curve away from the distractor. We experimentally reduced the ability to execute saccades by abducting the eye 30° into the temporal hemifield (monocular vision). This way the peripheral part of the temporal hemifield was located outside of the oculomotor range. Participants made a vertical eye movement while on some trials a distractor was shown either at a close or remote location in one of the hemifields. The results showed a decrease in curvature away from distractors located outside the oculomotor range. However, no such decrease was observed in the nasal hemifield, where saccade planning was unaffected. The results demonstrate that the inability to plan a saccade results in a decrease of distractor evoked activity in the oculomotor system even when the retinal stimulation is kept the same. The results are consistent with the premotor theory, which proposes that attention has emerged as an unavoidable consequence of movement planning. Meeting abstract presented at VSS 2016