Object-based attention in patients with left and right hemisphere lesions

Abstract

Since Egly, Driver and Rafal's (1994) pioneering study of object-based attention, their two-object cueing design has been widely used to study space- and object-based attentional orienting. Here, patients with unilateral brain injury performed target detection in a modified version of the two-object cueing task. By obliquely orienting the two rectangular objects ±45°, we were able to measure cueing performance separately at midline, in the contralesional field, and in the ipsilesional field. Cues were 64% predictive and always appeared in an upper or lower midline location. For targets appearing at midline locations, RTs were faster at the cued than uncued locations, as expected. When targets appeared laterally to the right or left of fixation, performance was modulated by the configuration of the objects in the display, but in opposite ways on the contralesional and ipsilesional sides. Reaction times (RTs) on the ipsilesional side were in the predicted direction: faster to targets in cued objects than in uncued objects. Conversely, RTs to contralesional targets were slower in cued objects than in uncued objects. The left and right hemisphere groups did not differ from each other in this respect. In sum, both patient groups revealed contralesional object-based neglect while demonstrating the opposite, but expected, object-based facilitation effect in their ipsilesional field. These findings will be related to the anatomical structures lesioned in this group of patients as well as to previous studies of lateralized attentional orienting and theories of hemispheric asymmetries in attentional orienting.

Footnotes

 LCR: NIH MH62331 and VA Merit Grant AL: NIH F31 NS047836 AVF and JLB: NIH T32 MH62997 TMV: VA Merit Grant.