Neglect after right hemisphere stroke: a smaller floodlight for distributed attention.

Objective: To learn whether there was a defect in an attentional floodlight. We used a line decision task for which subjects had to decide if two line segments separated by a gap were one line or two parallel lines. We varied the area of the gap and, therefore, the area over which subjects needed to spread attention to perform the task correctly.
Background: Visual tasks requiring focused attention use an attentional spotlight. Other visual tasks requiring spatially distributed attention may require a floodlight. Neglect after right hemisphere stroke can be associated with a defect in the attentional spotlight.
Results and Conclusions: Two patients with neglect after right hemisphere stroke performed more poorly than normal control subjects and left hemisphere-damaged control subjects as the area of spread in the gap increased. Right hemisphere-damaged patients did not differ from control subjects' performance on another visuospatial parameter--the degree of discontinuity between the line segments. These results support a defective attentional floodlight in neglect.