The missing link: the role of interhemispheric interaction in attentional processing.

Although interhemispheric interaction via the callosum is most often conceived as a mechanism for transferring sensory information and coordinating processing between the hemispheres, it will be argued here that the callosum also plays an important role in attentional processing. Experiments will be presented that support this viewpoint, both when attention is conceptualized as a resource and when it is conceptualized as a selective mechanism for gating sensory information. Interhemispheric interaction is posited to aid attentional processing because it allows for a division of labor across the hemispheres, and allows for parallel processing so that operations performed in one hemisphere can be insulated from those executed in the other. Given this additional role for interhemispheric processing, it is suggested that the corpus callosum should be considered a component in the network of neural structures that underlie attentional control.