Mechanisms of object-based attention (OBA) are commonly associated with the cerebral cortex. However, less is known about the involvement of lower visual pathways in these processes. In the current study, the classic double-rectangle cueing task (Egly et al., 1994) was implemented in a stereoscope, in order to differentiate between the involvement of lower (monocular) and higher (binocular) visual pathways in OBA processes. We found that there was a functional role for subcortical structures in two main aspects of OBA: in the process of exogenous orienting towards an object (Experiment 1; N =34); and in the process of attentional deployment within objects (Experiment 2; N =32). Thus, it seems that subcortical visual regions are not simply passing information to higher cortical areas but have a functional computational role in OBA. These findings emphasize the importance of subcortical regions in attentional processes and, more specifically, in OBA.

Object-based attention (OBA) can -in addition to acting upon explicit object representations -act upon occluded and illusory objects. It remains unknown, however, whether or not the selection of such object representations is detectable at the same level within visual cortex. This study examined the level within visual cortex (V1-V3, LOC) at which object-based selection is observed for explicit, occluded and illusory objects. During fMRI acquisition, participants identified a target preceded by a predictive arrow cue in the double-rectangle cueing paradigm. We independently localized retinotopicallyspecific regions of cortex corresponding to all possible target locations to examine neural fluctuations at each level of the visual cortical hierarchy. We found, after cue onset, that activity along visual cortex was not greater for representations of cued than of uncued same object locations. In contrast, we found that activity in V3 was enhanced at retinotopic representations that correspond to uncued same than different object locations. These results, together, support attentional spreading. Additionally, when the target appeared at either the cued or uncued locations, we found higher activation in areas representing uncued same object versus cued locations. This effect emerged along the visual cortical hierarchy. Further, when the target appeared on either the cued or uncued object, we found that activation in V3 transiently increased at uncued same than different object locations. This effect was also detectable upstream in LOC. These results index attentional re-orienting between locations/objects. Effects emerged regardless of object type: explicit or completed. Thus, the gating of object information proceeds completion.