Object-based attention (OBA) can - in addition to acting upon explicit object representations - act upon occluded objects and those defined by subjective contours. Thus, perceptual completion may precede the allocation of OBA. It remains unknown, however, whether or not such degraded object representations are selected at the same cortical level as explicit object representations. Such an investigation may indicate where in the visual cortical hierarchy perceptual object formation occurs. This study sought to ascertain the level within V1-V3 at which object-based selection is first observed for explicit versus degraded (occluded, illusory) objects. During fMRI acquisition, participants identified a target preceded by a predictive central arrow cue in the double-rectangle cueing paradigm. Behaviorally, participants identified the target faster when it appeared at the invalid-same versus invalid-different object location. This same-object advantage emerged regardless of object type, but, commensurate with recent data, was present only when objects were oriented horizontally. We independently localized retinotopically-specific regions of cortex corresponding to all possible target locations to examine neural fluctuations in each region of the visual cortical hierarchy. Consistent with our behavioral data, activation in V1 following cue onset increased within representations of the invalid-same versus invalid-different object location, which indicates prioritization of the same object location. This effect in V1 was restricted to horizontal objects. No such cue-evoked OBA effects were present in V2/V3. Additionally, activation in V1 following target onset increased when targets appeared in the invalid-different versus invalid-same object location. This effect, which may indicate a mismatch between where participants expected the target to appear, and the location in which it actually appeared, was evident only in representations of the invalid-same object location. No such target-evoked OBA effects were present in V2/V3. Thus, object-based selection occurs early in the visual cortical hierarchy, and does not depend on explicit object representations.
|Number of pages||1|
|Journal||Journal of Vision|
|Publication status||Published - Aug 2017|