Saccade trajectories deviate away from spatial, and not retinal, location of nearby tactile distractors

The abrupt appearance of a stimulus typically elicits a reflexive saccade towards it. However, when individuals are voluntarily moving their eyes to another location, the appearance of this distractor stimulus can instead cause the trajectory of the saccade to curve. Here we studied how visual and tactile distractors influence the trajectories of eye-movements in a double-step task. Participants made two consecutive saccades (a horizontal followed by a vertical) during which a visual (LED) or tactile (vibration to the index finger) distractor could occur either before or after the first saccade. The results confirmed that, as with a visual distractor, the occurrence of a tactile distractor prior to an eye-movement caused the trajectory of the saccade to curve away from the distractors position. Additionally, with conditions in which the spatial and retinal locations of where the distractor had been shown were dissociated, we were able to demonstrate for both modalities that saccades curved away from the spatial position. We also examined whether crossing the hands, so that a tactile distractor on the left finger would occur on the right side of space and vice versa, influenced the direction of the curvature. In contrast to the curvature found when the hands were canonically arranged, in the crossed hands condition tactile distractors caused attenuated or no curvature of the saccade. Overall these results suggest that although both visual and tactile distractor signals compete with the representation of the saccade target within an oculomotor map, the representation for tactile distractors may not fully compensate for irregular limb position. Meeting abstract presented at VSS 2016