Brain imaging of attentional networks in normal and pathological states.

The ability to image the human brain has provided a new perspective for neuropsychologists in their efforts to understand, diagnose, and treat insults to the human brain that might occur as the result of stroke, tumor, traumatic injury, degenerative disease, or errors in development. These new findings are the major theme of this special issue. In our article, we consider brain networks that carry out the functions of attention. We outline several such networks that have been studied in normal and pathological states. These include networks for orienting to sensory stimuli, for maintaining the alert state, and for orchestrating volitional control. There is evidence that these networks have a certain degree of anatomical and functional independence, but that they also interact in many practical situations. Damage to each of these networks, irrespective of the source, produces distinctive neuropsychological deficits. We consider the links between the etiology of the injury and changes in cognition and behavior and examine the role of brain imaging in the study of rehabilitation.