Abstract
Observers deploy covert attention as a means of winnowing the complexity of visual scenes into manageable input that can be processed efficiently. The well-established ‘two rectangle paradigm’ has been widely used to characterize space- and object-based attention, associated with highlighting a particular spatial position or a particular object, respectively (Egly et al., 1994). Neuroimaging and neuropsychological studies have ascribed space-based attention predominantly to the fronto-parietal network in the right hemisphere (RH; e.g., Schotten et al., 2011) and object-based attention primarily to the left hemisphere (LH; e.g., Orlandi & Proverbio, 2019). Here, we address whether this hemispheric asymmetry is a fixed property of the RH versus LH or is amenable to functional reorganization in individuals who have only a single hemisphere. 23 participants with childhood hemispherectomy (9 with preserved LH and 14 with preserved RH) for the management of drug-resistant epilepsy, completed a modified, age-appropriate two-rectangle paradigm (“Help Doug the dog figure out the color of the missing ball”), comprised of 70% valid trials (cue and target in same location), 10% invalid space (cue and target at same end of two different rectangles), 10% invalid object (cue and target at different ends of the same rectangle) and 10% neutral trials (four rectangle ends cued, target position random). Both patient groups performed significantly better for the valid than other conditions on both accuracy and reaction time measures, which did not differ from each other. Interestingly, there was no main effect of patient group (side of resection). These surprising results indicate that either hemisphere can mediate both types of attention without hemisphere-specific advantages after loss of an entire hemisphere, perhaps reflecting plasticity and functional reorganization in childhood.