Search

Background: Some studies have suggested that in stroke patients, spatial inattention on the cancellation test is closely related to disorganized visual search. However, methods to assess spatial aspects of search organization on cancellation tests have not been well developed. In this study the authors design and evaluate new methods to quantify strategies of spatial exploration on the cancellation test in stroke patients who showed a broad range of spatial attentional abilities, and test whether disorganization and inattention are related., Methods: Twenty stroke patients were videotaped while they performed a cancellation test. Several variables that reflect spatial aspects of search organization were measured through subsequent video playback. Two patients with severe neglect were excluded from further analysis to avoid constraining the spatial expression of search organization. Spearman correlations were used to assess whether severity of spatial inattention correlated with the individual search organization measures., Results: Of the 18 remaining patients, 10 had mild-moderate spatial neglect (pathologic inattention), while the other 8 omitted at most one target (normal performance). There were no significant correlations between the number of targets omitted and any of the search organization measures., Conclusions: Spatial inattention on cancellation due to neglect following stroke is not closely related to the organization of visual search. Instead, search disorganization during cancellation may reflect disturbance of an unspecified executive control mechanism.

Patients with neglect erred toward the right when attempting to locate the intercepts of their midsagittal planes with a horizontal line placed in front of them. When control subjects could not see their bodies, they also pointed to the right. While control subjects improved when they were able to see their bodies, neglect subjects did not. When the horizontal line was moved toward the right, both neglect and control subjects increased their rightward pointing errors. However, patients with neglect made greater errors than did controls. When the line was in far left hemispace, controls pointed accurately to their midsagittal planes. The neglect subjects, in contrast, erred toward the left. Our results suggest that patients with neglect from right hemisphere lesions are not only inattentive to their bodies, but are also distracted by extracorporeal stimuli, especially on the right. Our results also suggest that normal subjects have a propensity to orient to or be distracted by stimuli in right hemispace.

Patients with hemispatial neglect fail to cancel lines distributed on one side of a piece of paper. This defect is thought to be induced by a deficit in the neuronal systems that mediate attention, intention, and exploration toward and in the hemispace contralateral to the lesion. However, an alternate (but not mutually exclusive) interpretation is that the patients are either strongly attracted to or impaired in disengaging from the stimuli occupying the other, non-neglected hemispace. We tested ten patients with neglect on two versions of a cancellation test. In the control test they cancelled lines by drawing over them, and in the experimental test they erased lines. There were significantly more omissions in the drawing-over task than in the erasing task. The improved performance when lines were cancelled by removal instead of by marking them suggests that hemispatial neglect is influenced by the presence of stimuli in the non-neglected hemispace.