For example, given an attentional control system in which the sum of the weights across hemispheres dictates Trametinib molecular weight the current locus of selection, a perturbation in form of a transitory ‘virtual lesion’ induced

by transcranial magnetic stimulation (TMS) over one hemisphere should lead to an attentional shift toward the ipsilateral visual field. Conversely, bilateral stimulation should not change the overall attentional weighting balance, and hence nor the locus of selection. These predictions were recently confirmed in a study that used a multimodal approach of behavioral testing, neuroimaging and fMRI-guided TMS [16•]. First, individual differences in the estimated strengths of frontoparietal attentional weights were predictive of behavior when allocating spatial attention. Second, causal evidence in support of the ZD1839 purchase account’s predictions was established by demonstrating that space-based attention could be systematically shifted toward either visual field, depending on the site (unilateral or bilateral IPS1-2, or right SPL1) of a single

TMS pulse, presumably due to temporary changes to the attentional weights in underlying cortex. Thus, in the intact human brain, space-based attention appears to be controlled through competitive interactions between hemispheres. Having established a retinotopic organization of the frontoparietal network which in turn supports a contralaterally biased representation of space, an intriguing subsequent line of inquiry explored how a region of space is favorably prioritized for selection. Space-based selection is a complex process that is driven by the combination of sensory input and internal behavioral goals, the sum of which may be represented Flavopiridol (Alvocidib) via dynamic spatial priority maps 17, 18 and 19]. Such a priority map effectively grades spatial locations in accordance with top-down and bottom-up properties, and presumably, specific stimuli and task demands that gave rise to a particular pattern of prioritization should be indistinguishable within it. To test whether spatial priority maps

may be localized within the frontoparietal attention network, Jerde et al. [19] conducted a neuroimaging study in which one group of subjects completed a series of tasks designed to tax covert spatial attention, spatial working memory, or saccadic planning. Using a classifier trained on patterns of activation elicited from any one of the tasks, the experimenters found that spatial priorities could be accurately decoded from the remaining two tasks in both IPS2 and FEF. Neuronal populations within these two regions therefore likely signal prioritized space in a task-independent manner, such that selected locations are represented, while stimulus and task properties that drive selection are not.