Motion induced blindness is affected by head-centered and object-centered mechanisms

In Motion-induced-blindness (MIB; Bonneh et. al., Nature 2001), a salient static pattern may disappear and reappear spontaneously in the presence of a global moving pattern. We have previously showed that this phenomenon is unlikely to reflect retinal suppression, sensory masking or adaptation, but the mechanisms involved in MIB are largely unknown. Recent evidence suggests that parietal mechanisms representing space in different reference frames may be involved in the control of awareness, and possibly in MIB. Here we ask in what frame of reference does the disappearance during MIB occur. To answer this question we measured the magnitude of disappearance at different spatial locations in three different conditions: (1) retinotopic mapping in which a single target dot was presented at different locations relative to fixation, (2) a head-centered condition in which the direction of the head was displaced by 20 deg. to the right or left keeping direct fixation and (3) object-centered condition in which a target dot in fixed retinal location was surrounded by an elliptic contour with different relative displacement along it's main axis. Results show the effect of all three manipulations. Anisometropic disappearance was found for most observers with more disappearance in the upper and upper-left visual fields. The disappearance map changed for different angles of head rotation even though the retinal locations were identical. The elliptic contour induced more disappearance around its focal points and less in its center. These results suggest that disappearance in MIB involves or affected by head-centered and object-centered mechanisms.