Gaze orientation during full-field and peripheral field passive optokinesis

During full-field optokinetic nystagmus the mean position of gaze shifts the eyes in the direction of the fast phase. The driving force for this, pre-supposes that the preferred locus for the position control system, is shifting gaze into the direction where the motion is coming from. In this study, six subjects were examined to determine whether the absence of the central visual field would influence the mean position of gaze during passive optokinesis. Our findings indicate that a full field and a central field restricted to 20 deg, evoked gaze shifts of up to 7 deg into the direction of the fast phase. However, when the central field was masked by either 12.5 deg or 25 deg the mean gaze position was found to be significantly reduced (p < 0.05). This effect was not influenced by the velocity of the stimulus (p > 0.05). These results lead us to conclude that gaze orientation during optokinesis is strongly influenced by the area of retina stimulated. The role of the slow eye movement control system and possible cognitive strategies adopted during selective spatial attention are discussed in the light of this finding.