Detailed analyses of reading and nonlexical tasks by three patients wi
th unilateral spatial neglect (USN) secondary to stroke indicate that
the USN in each of these patients affects the left side (contralateral
to brain damage) of the viewer, with respect to the viewer's head, mi
d-sagittal plane of the body, or line of sight. In one case, the negle
ct was further specified as concerning the left side of the viewer's l
ine of sight (the left half of her residual visual field). Thus, the f
rame of reference of USN in these three cases appears to have viewer-c
entered (in at least one case, specifically retinotopic) coordinates.
The performance of these patients is contrasted to that of other patie
nts in the literature whose USN appears to have a frame of reference w
ith stimulus-centered or object-centered coordinates. These results ar
e interpreted within a model of visual processing (adapted from Marr,
1980 and others) with at least three coordinate frames. It is argued t
hat USN can affect one or more of these coordinate frames independentl
y. (C) 1998 Academic Press.