Distinct processes in line bisection according to severity of left unilateral spatial neglect.

We investigated the line bisection performances in 24 patients with left unilateral spatial neglect. They bisected lines of two lengths in three positions relative to the sagittal midplane of the body. The results showed that in the mild or moderate neglect patients, length and spatial locations of the lines affected the placement of the subjective midpoint. In the severe neglect patients, however, length had little effect on their performances, and location of the right endpoint in the egocentric space mainly determined the subjective midpoint. The line bisection process of the severe neglect patients was not only quantitatively but also qualitatively different from that of the mild or moderate cases.