title: Shifting attention in viewer- and object-based reference frames after unilateral brain injury.
abstract: The aims of the present study were to investigate the respective roles that object- and viewer-based reference frames play in reorienting visual attention, and to assess their influence after unilateral brain injury. To do so, we studied 16 right hemisphere injured (RHI) and 13 left hemisphere injured (LHI) patients. We used a cueing design that manipulates the location of cues and targets relative to a display comprised of two rectangles (i.e., objects). Unlike previous studies with patients, we presented all cues at midline rather than in the left or right visual fields. Thus, in the critical conditions in which targets were presented laterally, reorienting of attention was always from a midline cue. Performance was measured for lateralized target detection as a function of viewer-based (contra- and ipsilesional sides) and object-based (requiring reorienting within or between objects) reference frames. As expected, contralesional detection was slower than ipsilesional detection for the patients. More importantly, objects influenced target detection differently in the contralesional and ipsilesional fields. Contralesionally, reorienting to a target within the cued object took longer than reorienting to a target in the same location but in the uncued object. This finding is consistent with object-based neglect. Ipsilesionally, the means were in the opposite direction. Furthermore, no significant difference was found in object-based influences between the patient groups (RHI vs. LHI). These findings are discussed in the context of reference frames used in reorienting attention for target detection.
authors.affiliation: Department of Veterans Affairs Northern California Health Care System, Martinez, CA 94553, USA.
authors.forename: Alexandra
authors.initials: A
authors.lastname: List
authors.forename: Ayelet N
authors.initials: AN
authors.lastname: Landau
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Brooks
authors.forename: Anastasia V
authors.initials: AV
authors.lastname: Flevaris
authors.forename: Francesca C
authors.initials: FC
authors.lastname: Fortenbaugh
authors.forename: Michael
authors.initials: M
authors.lastname: Esterman
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Van Vleet
authors.forename: Alice R
authors.initials: AR
authors.lastname: Albrecht
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Alvarez
authors.forename: Lynn C
authors.initials: LC
authors.lastname: Robertson
authors.forename: Krista
authors.initials: K
authors.lastname: Schendel
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001288:Attention / Q000502:physiology*; D001930:Brain Injuries / Q000209:etiology / Q000523:psychology*; D003463:Cues; D004569:Electroencephalography; D005133:Eye Movements / Q000502:physiology; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009949:Orientation; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D011932:Reading; D020521:Stroke / Q000150:complications / Q000523:psychology; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000523:psychology; D014796:Visual Perception / Q000502:physiology*