To the edge of gaze and beyond: Visual distraction outside the oculomotor range

Abstract

Neurophysiological studies demonstrated that attentional orienting is performed by fronto-parietal brain areas which also play an important role in oculomotor control (e.g. LIP, FEF). Accordingly, several studies claimed that exogenous attention can only be allocated to where we can potentially make an eye movement, i.e. within the oculomotor range. We tested this assumption by assessing the disruptive effect of a salient distractor at locations within and beyond participants' oculomotor range. Participants rotated their heads ~38° leftwards to prevent them from performing large rightward saccades. The required head rotation angle was determined individually prior to the experiment and monitored with an electromagnetic motion tracking device. In this posture, participants fixated the screen center and focused their attention on a location on the left side of the screen, where they had to discriminate the orientation of a visual noise patch. While assessing visual orientation sensitivity — an established proxy of visual attention — at this endogenously attended location, we flashed a salient cue either at the attended location or at various locations inside or outside their oculomotor range. We found that whenever the salient cue occurred at a location other than the endogenously attended location, it withdrew visual attention and significantly hampered endogenous attentional orienting. Crucially, this disruptive effect occurred regardless of whether the cue was presented within or beyond participants' oculomotor range, demonstrating that exogenous events equally grab our attention both inside and outside the oculomotor range. Since spatial exogenous attention was attracted unrestrictedly toward locations to which no saccade could be executed, the coupling of attention and eye movement control presumably is less tight than, for example, the prominent Premotor Theory of Attention would suggest. Rather, attention can be shifted freely over the entire visual range, independent of pathological and physiological limitations of the eye movement system.