Structural connectivity for visuospatial attention: significance of ventral pathways.

In the present study, we identified the most probable trajectories of point-to-point segregated connections between functional attentional centers using a combination of functional magnetic resonance imaging and a novel diffusion tensor imaging-based algorithm for pathway extraction. Cortical regions activated by a visuospatial attention task were subsequently used as seeds for probabilistic fiber tracking in 26 healthy subjects. Combining probability maps of frontal and temporoparietal regions yielded a network that consisted of dorsal and ventral connections. The dorsal connections linked temporoparietal cortex with the frontal eye field and area 44 of the inferior frontal gyrus (IFG). Traveling along superior longitudinal and arcuate fascicles, these fibers are well described in relation to spatial attention. However, the ventral connections, which traveled in the white matter between insula (INS) cortex and putamen parallel to the sylvian fissure, were not previously described for visuospatial attention. Linking temporoparietal cortex with anterior INS and area 45 of IFG, these connections may provide an anatomical substrate for crossmodal cortical integration needed for stimulus perception and response in relation to current intention. The newly anatomically described integral network for visuospatial attention might improve the understanding of spatial attention deficits after white matter lesions.