While this suggests a seemingly broad connectivity pattern between PPC and FEF, separable pathways may be functionally distinct. Evidence for functional specialization distributed within the frontoparietal network has been found in a study that examined connectivity patterns of different network nodes [42••]. Two pathways between frontal cortex and PPC were identified using diffusion tensor imaging (DTI) and probabilistic tractography, and functional interactions of activity evoked during attention tasks: first, a lateral

pathway connecting FEF and IPS2 and second, a medial pathway connecting the supplementary eye field (SEF) and SPL1 (Figure 3). Intriguingly, Caspase-dependent apoptosis these two pathways appear to mediate different functions. The IPS2-FEF pathway

supports attentional selection in retinotopic, or viewer-centered spatial coordinates, whereas the SEF-SPL1 pathway supports attentional selections based on an object-centered spatial reference frame. Thus, Trametinib supplier the multiple topographic representations in PPC may code for attentional priorities in different spatial reference frames. In sum, a growing body of research demonstrates the broad involvement of frontoparietal cortex in space-based, feature-based, object-based, and category-based selection, Tyrosine-protein kinase BLK consistent with the possible existence of domain-general control centers within the human control network (see Figure 2). An important question that remains unresolved is how a single network can flexibly generate a diverse range of control signals depending on current task demands. Further studies are needed to determine whether separable selection mechanisms are subserved by true domain-general neuronal populations or whether each mechanism recruits distinct subpopulations of neurons within the same regions 23 and 26]. Relatedly,

it remains an open question what individual roles subregions within the network may play in the generation of attentional control signals. The existence of 14 topographic representations in human PPC alone seems, on the face of it, excessive and redundant. As such, an investigation into potential functional dissociations between subunits is warranted. DTI studies lend some support to this line of inquiry, as IPS can be largely subdivided based on structural connectivity patterns alone 37 and 40]. Given that the functional properties of a brain region are necessarily constrained by its anatomical connections, these data imply that subunits of IPS may very well be functionally distinct, but carefully implemented imaging studies are necessary to confirm this hypothesis.