Nearly every topographic region of the left and

right hemisphere contributes to the control of space-based Daporinad cost attention across the visual field by generating a spatial bias, or ‘attentional weight’ [9] in favor of the contralateral hemifield. The sum of the weights contributed by all areas within a hemisphere constitutes the overall spatial bias exerted over contralateral space, and the net output of the two hemispheres is similar, resulting in a balanced system. This balance of attentional weights across the hemispheres may be achieved through reciprocal interhemispheric inhibition of corresponding areas [10]. However, the higher-order control system appears to be somewhat complicated by right SPL1′s unique role in spatial attention, as the attentional weight generated by this area was not found to be counteracted by left SPL1. Instead, the left frontal eye field (FEF) and left intraparietal sulcus (IPS) areas IPS1-2 generated stronger attentional weights than the corresponding regions in the right hemisphere. Thus, the control system likely requires the cooperation of several distributed subcomponents in order to achieve balance across the two hemispheres. The interhemispheric competition account of

space-based attentional control is in stark contrast to the prevailing hemispatial theory [11], which assumes that GPCR Compound Library concentration the right hemisphere controls attention in both visual hemifields, whereas the left hemisphere controls attention in the contralateral visual field only. This hypothesized asymmetry across hemispheres received a groundswell of support primarily from patient studies with unilateral lesions in the inferior parietal lobule and/or the temporoparietal

junction 12 and 13]. These patients typically exhibit symptoms of visuo-spatial hemi-neglect to the contralesional side of space, but such deficits manifest with an overwhelmingly higher rate following right, rather than left, hemispheric damage. Verteporfin purchase A similar breadth of clinical evidence in favor of interhemispheric competition is largely lacking, presumably due to the unlikely occurrence of focal lesions contained within IPS. Recently, however, two such cases were reported 14 and 15]. Patients H.H. and N.V. have a focal lesion confined to left posterior IPS and right middle IPS (extending into SPL), respectively, and both exhibited attention-related deficits examined in a modified Posner cuing task. Here, subjects reported the orientation of a grating following an endogenous precue; on a proportion of trials, a competing distractor appeared in the uncued location. Behavioral deficits attributed to stimulus competition were present for both H.H. and N.V. despite having lesions in opposite hemispheres. Importantly, deficits were restricted to trials in which the target appeared in the contralesional side of space.